This page shows what was measured, who it was measured in, and what that does not settle.
What Hydroxychloroquine does in the body
Lupus, rheumatoid arthritis, and malaria where the parasite is still susceptible
Hydroxychloroquine is a weak base, which means it drifts into any acidic pocket inside a cell and gets stuck there, raising the pH of that pocket. In the malaria parasite, the acidic pocket is the stomach where it digests haemoglobin, and raising the pH poisons it with its own waste. In an immune cell, the acidic pocket is the endosome, where the sensors that detect foreign DNA and RNA live — and in lupus, those sensors are being triggered by the body’s own DNA. Raising the endosome pH is thought to turn the volume down on that false alarm. The prescribing information does not commit to this: it says the mechanisms in rheumatoid arthritis and lupus are not fully known.
What happened in people
Mean absolute oral bioavailability 79% and a whole-blood to plasma concentration ratio of roughly 2.6
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The recorded finding that sits closest to something a person would notice. Written into the record, not signed off, and it carries no population or interval.
Hydroxychloroquine sulfate tablets United States prescribing information — Indications 1.1 to 1.4 with Limitations of Use, Warnings and Precautions 5.1 to 5.… · a recorded source, not a stored snapshot
The 2020 demand surge caused shortages for people taking it for lupus and rheumatoid arthritis, in whom it is not readily substitutable
Where it acts
Acidic intracellular compartments — the parasite’s digestive vacuole in malaria, and the endosome of immune cells in the autoimmune indications
Kind of result
A step measured inside a person
Supervision
RNAWiki has not recorded a supervision or regulatory status for this substance.
What the registries record it as
Its recorded molecular formula is C18H26ClN3O•H2SO4.
US prescribing information · 805a1acd-2e0d-48f1-af6b-0e5d8e06c228 · read 2026-08-30
Where each sentence above came from
No recorded sentence describes the change this makes in a way that stands on its own. The page opens with what it is taken for instead, and the recorded explanation follows below.
Shown as the opening line on this page.
A limit recorded against this substance. Not signed off as a reviewed claim.
The four opening statements run to 148 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Stand-in result
A stand-in result is a number measured because the real result takes too long.
A picture of it, and where the picture fails
It is like judging a journey by the speedometer rather than by arriving.
Where that stops being true. Speed does predict arrival. Many stand-in results do not predict the real one.
What people get wrong. A stand-in result is often reported as the result itself.
A surrogate endpoint substituted for a clinical endpoint, valid only where the substitution has been shown to hold.
Randomisation
Randomisation means chance decides who gets which treatment.
A picture of it, and where the picture fails
It is like a coin toss deciding the groups.
Where that stops being true. A coin toss is fair once. Fairness here comes from doing it for everyone.
What people get wrong. It is thought to make groups identical. It makes them similar on average, including on things nobody measured.
Allocation of participants to arms by a chance process, so that unmeasured factors are balanced in expectation.
Confidence interval
A confidence interval is the range the true answer is likely to sit in.
A picture of it, and where the picture fails
It is like a weather forecast giving a range rather than one number.
Where that stops being true. A forecast range covers tomorrow. This one covers what the study could resolve.
What people get wrong. The middle number is read as the answer. A range crossing zero means no change is still possible.
An interval estimate that would contain the true parameter in a stated proportion of repeated studies.
Pathway
A pathway is a chain of steps inside a cell, each one setting off the next.
A picture of it, and where the picture fails
A pathway is like a row of dominoes.
Where that stops being true. Dominoes fall one way. Pathways loop back and can switch themselves off.
What people get wrong. Changing one step is read as changing the outcome. Other steps often absorb it.
An ordered series of molecular interactions producing a defined cellular change.
What happened in people◇Read from sources, not yet reviewed
What was measured, goal by goal
One row for each goal a registered study measured something for. One column for each kind of thing that could be measured.
Registered studies list 40 outcome measures that RNAWiki could read. A registered study says what someone planned to measure. It does not say what they found. 0 of the matched studies tested this substance, and 0 posted a result.
There is no single score. A strong test result and a weak life result are different facts.
Goals down the side, kinds of measurement across the top. Each cell says what kind of thing was registered, not what was found.
Goal
Life outcome
What a body can do
How a person feels
A test result
A step in the body
Harms
How long
Who was studied
Blood sugar
∅Nothing in the sources checkedNo registered study lists a life outcome for this goal.
∅Nothing in the sources checkedNo registered study lists a performance measure for this goal.
∅Nothing in the sources checkedNo registered study lists a symptom measure for this goal.
△Only a number moved3 registered test measure.
∅Nothing in the sources checkedNo registered study lists a body-step measure for this goal.
—Not recordedHarms were not a registered measure for this goal.
—Not recordedNo finished study window is recorded.
…Waiting for a reviewerWho was studied is listed further down the page.
Pain
∅Nothing in the sources checkedNo registered study lists a life outcome for this goal.
∅Nothing in the sources checkedNo registered study lists a performance measure for this goal.
…Waiting for a reviewer1 registered symptom measure.
∅Nothing in the sources checkedNo registered study lists a test result for this goal.
∅Nothing in the sources checkedNo registered study lists a body-step measure for this goal.
—Not recordedHarms were not a registered measure for this goal.
—Not recordedNo finished study window is recorded.
…Waiting for a reviewerWho was studied is listed further down the page.
Healthy ageing
…Waiting for a reviewer1 registered study measure of this kind. No reviewed result yet.
∅Nothing in the sources checkedNo registered study lists a performance measure for this goal.
∅Nothing in the sources checkedNo registered study lists a symptom measure for this goal.
∅Nothing in the sources checkedNo registered study lists a test result for this goal.
∅Nothing in the sources checkedNo registered study lists a body-step measure for this goal.
—Not recordedHarms were not a registered measure for this goal.
—Not recordedNo finished study window is recorded.
…Waiting for a reviewerWho was studied is listed further down the page.
Which registered measures put each goal on this table
Relative risk of flare 2.5 (95% CI 1.08 to 5.58) on placebo — 16 of 22 against 9 of 25 — with shorter time to flare (p=0.02)
Repeated elsewhere
Partially Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. The severe-exacerbation relative risk of 6.1 had a 95% confidence interval of 0.72 to 52.44 and is not statistically significant, though it is frequently cited as though it were. The trial had 47 patients and ran for six months; it establishes that continuing the drug prevents flares in stable disease, not that starting it controls active disease.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet of hydroxychloroquine sulfate at 100, 200, 300 and 400 mg — a 200 mg sulfate tablet delivers 155 mg of hydroxychloroquine base — usually taken once or twice daily
Interval reported. 95% CI 1
Written into the record, not signed off as a reviewed claim.
Hydroxychloroquine sulfate tablets United States prescribing information — Indications 1.1 to 1.4 with Limitations of Use, Warnings and Precautions 5.1 to 5.… · a recorded source, not a stored snapshot
28-day all-cause mortality in patients hospitalised with COVID-19
✗ The study did not show it
Who was studied
RECOVERY hydroxychloroquine arm (N Engl J Med 2020;383:2030-2040; ISRCTN50189673)
How many people
4716
Study design
Randomised, controlled, open-label platform trial
Compared against
Not recorded for this study
Kind of result
Living longer, or avoiding a major event
What was found
421 of 1,561 (27.0%) against 790 of 3,155 (25.0%); rate ratio 1.09 (95% CI 0.97 to 1.23), p=0.15
Repeated elsewhere
Replicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. Discharge alive within 28 days was lower on hydroxychloroquine (59.6% against 62.9%; rate ratio 0.90, 95% CI 0.83 to 0.98), and among patients not ventilated at baseline, progression to invasive mechanical ventilation or death was higher (30.7% against 26.9%; risk ratio 1.14, 95% CI 1.03 to 1.27). The arm was closed early for lack of efficacy.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet of hydroxychloroquine sulfate at 100, 200, 300 and 400 mg — a 200 mg sulfate tablet delivers 155 mg of hydroxychloroquine base — usually taken once or twice daily
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
Hydroxychloroquine sulfate tablets United States prescribing information — Indications 1.1 to 1.4 with Limitations of Use, Warnings and Precautions 5.1 to 5.… · a recorded source, not a stored snapshot
Laboratory-confirmed COVID-19 or compatible illness within 14 days of a high- or moderate-risk exposure
✗ The study did not show it
Who was studied
Boulware DR et al., N Engl J Med 2020;383:517-525 (post-exposure prophylaxis)
How many people
821
Study design
Randomised, double-blind, placebo-controlled
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
49 of 414 (11.8%) against 58 of 407 (14.3%); absolute difference -2.4 percentage points (95% CI -7.0 to 2.2), p=0.35
Repeated elsewhere
Replicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. Side effects were more than twice as common on hydroxychloroquine (40.1% against 16.8%), with no serious adverse reactions reported.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet of hydroxychloroquine sulfate at 100, 200, 300 and 400 mg — a 200 mg sulfate tablet delivers 155 mg of hydroxychloroquine base — usually taken once or twice daily
Interval reported. 95% CI -7
Written into the record, not signed off as a reviewed claim.
Hydroxychloroquine sulfate tablets United States prescribing information — Indications 1.1 to 1.4 with Limitations of Use, Warnings and Precautions 5.1 to 5.… · a recorded source, not a stored snapshot
RNAWiki holds 3 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What happened in people◇Read from sources, not yet reviewed
How close this is to real life
The top step is something a person would feel or care about. The bottom is a guess from software. Filled steps are where evidence exists for this substance.
■Living longer, or avoiding a major eventEvidence recorded. Death, a heart attack, a stroke, a hospital stay.10 registered measures of this kind. No reviewed result.
■What a body can do day to dayEvidence recorded. Walking, dressing, breathing, recovering.1 registered measure of this kind.
■Measured performanceEvidence recorded. How much was lifted, how far was run, how fast.1 registered measure of this kind.
■Symptoms and quality of lifeEvidence recorded. Pain, tiredness, mood, sleep, as the person rated it.1 registered measure of this kind.
■A number that stands in for healthEvidence recorded. Cholesterol, blood sugar, bone density. A stand-in, not the thing itself.5 registered measures of this kind.
■A step measured inside a personEvidence recorded. Something measured in human tissue or human cells.A human record sits on the stored organism ladder.
■AnimalsEvidence recorded. Mice, rats, dogs. Useful for ideas, not proof about people.Stored records in Mouse. A result in animals says what to test next. It does not say what happens in people.
■Cells in a dishEvidence recorded. Cells or chemistry on a bench, far from a whole body.Stored mechanism abstracts describe steps measured in cells or tissue.
□A guess from softwareNo evidence recorded. Nobody measured it. RNAWiki never publishes one as a finding.RNAWiki stores no prediction for this record. Software can suggest a link. RNAWiki does not publish one as a finding.
Higher on these steps means closer to something a person would feel. It does not mean better done.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Start
Hydroxychloroquine
What a person takes: Oral tablet of hydroxychloroquine sulfate at 100, 200, 300 and 400 mg — a 200 mg sulfate tablet delivers 155 mg of hydroxychloroquine base — usually taken once or twice daily.
The measurement behind this step
Mean absolute oral bioavailability is 79% fasting and steady-state whole blood concentration is dose proportional from 200 to 400 mg daily. The drug distributes extensively into tissue and accumulates in acidic intracellular compartments, giving an elimination half-life measured in weeks and a time to steady state measured in months — which is why any benefit is slow to appear and any accumulated toxicity is slow to clear. Whole blood concentrations run roughly 2.6 times plasma concentrations.
Getting in
Well absorbed, and it hides in blood cells
About four-fifths of the tablet gets in. Once there, the drug concentrates inside blood cells, so a blood-cell measurement reads more than twice a plasma one.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Mean absolute oral bioavailability is 79% (SD 12%) fasting. After a single 200 mg sulfate tablet, whole blood Cmax is 129.6 ng/mL against a plasma Cmax of 50.3 ng/mL, with Tmax at 3.3 and 3.7 hours respectively. Kinetics are linear across the therapeutic range. Whole blood, not plasma, is the correct matrix for therapeutic monitoring.
Hydroxychloroquine sulfate tablets United States prescribing information — Indications 1.1 to 1.4 with Limitations of Use, Warnings and Precautions 5.1 to 5.… · a recorded source, not a stored snapshot
The molecule drifts freely through membranes until it meets an acidic pocket, where it picks up a proton, becomes charged, and can no longer get out.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Lysosomotropic accumulation: the neutral species diffuses across the membrane, is protonated at the low pH inside lysosomes and endosomes, and the charged form cannot cross back. Intracellular concentrations reach orders of magnitude above plasma, which is why the drug has an elimination half-life measured in weeks and takes months to reach steady state.
Hydroxychloroquine sulfate tablets United States prescribing information — Indications 1.1 to 1.4 with Limitations of Use, Warnings and Precautions 5.1 to 5.… · a recorded source, not a stored snapshot
Accumulating base neutralises the acid. Whatever depends on that compartment being acidic stops working properly.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
In Plasmodium the affected compartment is the digestive vacuole, where haemoglobin is broken down and the toxic free haem is polymerised into inert haemozoin; raising the pH blocks polymerisation and the parasite is poisoned by its own digestion product. In human immune cells the affected compartment is the endosome.
Hydroxychloroquine sulfate tablets United States prescribing information — Indications 1.1 to 1.4 with Limitations of Use, Warnings and Precautions 5.1 to 5.… · a recorded source, not a stored snapshot
In lupus, the proposed effect is on self-DNA sensing
The sensors that detect foreign DNA and RNA sit inside those same acidic pockets. In lupus they are being set off by the body’s own DNA. Raising the pH is thought to quiet them.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Toll-like receptors 7 and 9 signal from the endosome and require acidification for ligand binding and proteolytic maturation. Suppressing that pathway would reduce type I interferon output from plasmacytoid dendritic cells, which is the central pathway of lupus. Section 12.1 declines to state this, saying only that the immunomodulatory mechanisms are not fully known.
Hydroxychloroquine sulfate tablets United States prescribing information — Indications 1.1 to 1.4 with Limitations of Use, Warnings and Precautions 5.1 to 5.… · a recorded source, not a stored snapshot
The measured benefit is prevention. In the withdrawal trial, people who stopped it flared two and a half times as often as people who stayed on it.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Relative risk of clinical flare 2.5 (95% CI 1.08 to 5.58) on placebo against continued therapy over 24 weeks in 47 patients with stable disease, with shorter time to flare (p=0.02). The severe-exacerbation relative risk of 6.1 had a confidence interval of 0.72 to 52.44 and is not a significant result.
Hydroxychloroquine sulfate tablets United States prescribing information — Indications 1.1 to 1.4 with Limitations of Use, Warnings and Precautions 5.1 to 5.… · a recorded source, not a stored snapshot
The same trapping damages the retina and the heart
The drug also accumulates in the retina and in heart muscle, and over years it can cause damage that does not reverse when the drug stops.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Retinal toxicity is dose- and duration-dependent: prevalence 7.5% overall after five years of use, rising towards 20% after twenty years at 4.0 to 5.0 mg/kg. The label states retinal changes and visual disturbance may progress even after cessation. In heart muscle, endomyocardial biopsy in reported cardiomyopathy cases showed phospholipidosis without inflammation or necrosis — the same lysosomal accumulation, in a different tissue.
Hydroxychloroquine sulfate tablets United States prescribing information — Indications 1.1 to 1.4 with Limitations of Use, Warnings and Precautions 5.1 to 5.… · a recorded source, not a stored snapshot
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 6 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What it would be like to take◇Read from sources, not yet reviewed
Felt, measured, or meaningful
Three different things that get called the same word. Registered studies measured all three, and mixing them is how a blood test becomes a health claim.
Felt
Things a person could notice without a test.
pain intensity measured by 100 mm visual analog scale
Measured
Things only a test, a scale or a device shows.
insulin sensitivity index
insulin sensitivity
hemoglobin a1c
vascular inflammation as measured by fdg pet/ct at 6 months
glucose level
Meaningful
Things that change how a life goes, not only a number.
progression free survival
overall survival
2 month progression free survival rate
remission
health assessment questionnaire disability index at week 12
remission defined as cdai 150 maintained through to 24 weeks
remission defined as cdai 150 maintained through to 52 weeks
clinical remission
complete remission rate
all cause mortality
and 1 more.
A registered study says what someone planned to measure. It does not say what they found. A number moving is not the same as a life going better. The two are shown apart here.
Felt, but not shown to help. A person notices a change. No study showed it leads anywhere good.
Measured, but not felt. A number moves. The person notices nothing. Both can be true.
Measured, but not shown to matter. A number moves in the good direction. Nobody showed that lives went better.
Matters, but takes years. The result that counts may take longer than anyone would keep watching.
Names that fit none of the three (23)
disease activity erythrocyte sedimentation rate
48 week change in das28
overall response rate
prostate specific antigen response
overall response
tumor response rate
response
bioequivalence based on auc and cmax
that experienced a dose limiting toxicity
response rate
adverse events
dose limiting toxicity rate
treatment emergent adverse events
efficacy
safety number of adverse events
validated aid associated product technical failures
live birth
days alive and not receiving organ support in icu
micrornas expression level
timed 25 foot walk
These are harms, study-process measures, or names the rules did not recognise. They are shown rather than dropped.
What it would be like to take◇Read from sources, not yet reviewed
How long anything takes
Nine different lengths of time that get confused with each other. None of them is worked out from another.
Before anything is noticed.RNAWiki does not store this separately, and never works it out from another figure on this page.
Before a test result moves.RNAWiki does not store this separately, and never works it out from another figure on this page.
Before performance moves.RNAWiki does not store this separately, and never works it out from another figure on this page.
How long the result was watched.No finished study window is recorded for a study that tested this substance.
How long people took it.How long people actually took it is not stored. The study window is not the same thing.
How long people were followed.Follow-up length is not stored separately. It is never read off the study window, which would be a different thing.
How fast the body clears it. 40 to 50 days in whole blood
Read from the label, which states: “Following chronic oral administration of hydroxychloroquine, the absorption half-life of hydroxychloroquine was approximately 3 to 4 hours and the terminal half-life ranged from 40 to 50 days in whole blood.”
How long effects linger.RNAWiki does not store this separately, and never works it out from another figure on this page.
Beyond the studies. Nothing is recorded about the long term.
The longest finished study sets the edge of what anyone measured.
A study window is not how long people took it, and neither is how long they were followed. Where RNAWiki holds only one of the three, it shows one.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
Adults with systemic or discoid lupus, adults with rheumatoid arthritis, and travellers or residents in malarious areas where chloroquine resistance has not been reported. It is avoided in psoriasis, in porphyria, and in anyone with QT prolongation or the risk factors for it.
Who is missing from the studies
Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What the label states about particular groups
On pediatric, the label states: “The safety and effectiveness of hydroxychloroquine sulfate have not been established in pediatric patients for the treatment of rheumatoid arthritis, chronic discoid lupus erythematosus, or systemic lupus erythematosus.”
US prescribing information · 805a1acd-2e0d-48f1-af6b-0e5d8e06c228 · read 2026-08-30
On older people, the label states: “Clinical trials of hydroxychloroquine sulfate did not include sufficient numbers of patients 65 years of age and older to determine whether they respond differently from younger adult patients.”
US prescribing information · 805a1acd-2e0d-48f1-af6b-0e5d8e06c228 · read 2026-08-30
On people who are pregnant, the label states: “Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to hydroxychloroquine sulfate during pregnancy.”
US prescribing information · 805a1acd-2e0d-48f1-af6b-0e5d8e06c228 · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary Published lactation data report that hydroxychloroquine is present in human milk at low levels.”
US prescribing information · 805a1acd-2e0d-48f1-af6b-0e5d8e06c228 · read 2026-08-30
Where the result stopped carrying
No mortality benefit in hospitalised COVID-19, with fewer patients discharged alive and more progressing to ventilation or death
No benefit as post-exposure prophylaxis, with side effects in 40.1% against 16.8% on placebo
The retinopathy risk taught for forty years was found to be roughly an order of magnitude too low once modern imaging was used
Ideal body weight, the basis on which the drug had been dosed, predicted retinal risk less well than real body weight, and the dosing rule was rewritten
This is a scope explorer, not a diagnosis engine.
It shows who was studied so you can see whether people similar to you were included.
RNAWiki cannot tell whether a study fits you. It can show who was in it.
What it would be like to take◇Read from sources, not yet reviewed
Why it might seem to do nothing
A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.
It was studied for a different goal
The studies measured something else entirely.
On this record: Some registered studies measured things that match no goal on this page.
It was studied in different people
The people in the studies were not much like the reader.
On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
The evidence may simply be wrong
Small early studies often do not hold up.
On this record: RNAWiki has not yet published a reviewed conclusion for this use.
Other reasons RNAWiki checked and found nothing for (10)
A different form was studied
The studied form is not the form on the shelf. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
The change is too small to feel
A real change can still sit below what a person notices. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
The product may not be what it says
Contents of a sold product are not always what the label states. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.
None of these is a reason to take more. Taking more is not a step this page ever suggests.
What it would be like to take◇Read from sources, not yet reviewed
What taking it involves
The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.
How it is supplied
Prescription only
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
Oral tablet of hydroxychloroquine sulfate at 100, 200, 300 and 400 mg — a 200 mg sulfate tablet delivers 155 mg of hydroxychloroquine base — usually taken once or twice daily
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
RNAWiki has not recorded a supervision or regulatory status for this substance.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
No register row and no identity class settled the question.
No source is stored against this line.
What is in the pack
Mean absolute oral bioavailability is 79% fasting and steady-state whole blood concentration is dose proportional from 200 to 400 mg daily.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold. The rest of the recorded wording: The drug distributes extensively into tissue and accumulates in acidic intracellular compartments, giving an elimination half-life measured in weeks and a time to steady state measured in months — which is why any benefit is slow to appear and any accumulated toxicity is slow to clear. 6 times plasma concentrations.
No source is stored against this line.
Where it is registered
Regulatory records are listed in the technical disclosure at the foot of this page.
# Counted from records
Where this came from
A count of rows RNAWiki holds. It describes our records, not your body.
Register entries are stored per jurisdiction and shown with their dates.
No source is stored against this line.
Why people stop
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No record of why people stopped taking it is stored for this substance.
No source is stored against this line.
What it would be like to take◇Read from sources, not yet reviewed
What can go wrong
Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.
·Worth asking a clinician aboutWritten into the record from the studies named on this page
Section 5.1 warns of fatal and life-threatening cardiomyopathy, with endomyocardial biopsy in multiple cases showing phospholipidosis without inflammation or necrosis, and of QT prolongation and ventricular arrhythmias including torsades de pointes whose magnitude may rise with drug concentration; the drug is not recommended with other QT-prolonging agents and is to be avoided in known QT prolongation, heart failure, recent infarction, bradycardia below 50 beats per minute, prior ventricular dysrhythmia and uncorrected hypokalaemia or hypomagnesaemia. Section 5.2 warns of irreversible retinal damage related to cumulative dose and duration, with baseline and periodic ophthalmic examination, and notes that changes may progress after the drug is stopped. Also warns of Stevens-Johnson syndrome, toxic epidermal necrolysis, DRESS and acute generalised exanthematous pustulosis; directs avoiding the drug in psoriasis and in porphyria; and warns of myelosuppression and of renal phospholipidosis.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Where this came from
Hydroxychloroquine sulfate tablets United States prescribing information — Indications 1.1 to 1.4 with Limitations of Use, Warnings and Precautions 5.1 to 5.… · a recorded source, not a stored snapshot
These are reports people sent to a regulator. They do not show the medicine caused the reaction.
Nobody counted how many people took the medicine and reported nothing.
The same event can be reported more than once, and many reports are incomplete.
News coverage, lawsuits and new warnings change how often people report.
A count is not a rate and not a risk.
Hydroxychloroquine appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 22165 reaction mentions were counted. One report can name several reactions.
The recorded terms (10)
rheumatoid arthritis — 4232 reaction mentions
drug intolerance — 3086 reaction mentions
joint swelling — 2286 reaction mentions
pain — 2188 reaction mentions
arthralgia — 1902 reaction mentions
treatment failure — 1844 reaction mentions
synovitis — 1785 reaction mentions
fatigue — 1716 reaction mentions
condition aggravated — 1612 reaction mentions
rash — 1514 reaction mentions
open-targets-adr · recorded 2026-06-24 · a recorded source, not a stored snapshot
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear◇Read from sources, not yet reviewed
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Oral tablet of hydroxychloroquine sulfate at 100, 200, 300 and 400 mg — a 200 mg sulfate tablet delivers 155 mg of hydroxychloroquine base — usually taken once or twice daily
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
A recorded note compares this form with the others that are sold. It is kept below, word for word.
§ A fixed RNAWiki sentence
Where this came from
Wording RNAWiki always uses, not a finding about this substance.
The recorded note, unchanged: The drug distributes extensively into tissue and accumulates in acidic intracellular compartments, giving an elimination half-life measured in weeks and a time to steady state measured in months — which is why any benefit is slow to appear and any accumulated toxicity is slow to clear. Whole blood concentrations run roughly 2.6 times plasma concentrations.
No source is stored against this line.
What is recorded as being sold
72 products list this as an active ingredient in the United States drug directory. 72 of them contain it and nothing else.
FDA National Drug Code directory · 71335-2813 · read 2026-08-29
They are sold as powder, tablet and tablet, film coated, taken oral.
FDA National Drug Code directory · 71335-2813 · read 2026-08-29
The regulator's established pharmacologic class for it is antimalarial [epc] and antirheumatic agent [epc].
FDA National Drug Code directory · 71335-2813 · read 2026-08-29
50 published labels name it as an active ingredient. 50 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · a5b3455a-e842-7d4b-e053-2995a90adee3 · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · a5b3455a-e842-7d4b-e053-2995a90adee3 · read 2026-08-29
Hydroxychloroquine Sulfate is tablets, film-coated at 200 mg of hydroxychloroquine sulfate, recorded as prescription product; fda label in effect 2025-10-09 in the United States.
US prescribing information · 04139607-f7c0-4fe1-a210-ffa5af347d56 · read 2026-08-27
Recorded price in US: 0.14854–0.63694 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 32 priced products whose strengths and pack forms differ, as of 2026-08-26, paid by retail pharmacies buying the product, as surveyed by the Centers for Medicare & Medicaid Services. It is not a list price, an insurance price, or what anyone pays at a counter..
Recorded source · 2026-08-26 · read 2026-08-28
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
RNAWiki could not confidently classify this substance, so no self-experiment plan is offered.
Questions worth asking
Which of the trials of Hydroxychloroquine studied people like me?
What was measured, and for how long?
Was the result a laboratory value or a health outcome?
What would we watch for, and when would we stop?
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki records evidence. It does not say whether this substance is right for you.
What is missing or unclear◇Read from sources, not yet reviewed
Claims that go past the evidence
Things said about this substance that sound reasonable, and the exact step that is missing between the evidence and the claim.
✗Goes past the evidence
That hydroxychloroquine works in lupus by alkalinising endosomes and suppressing Toll-like receptor 7 and 9 signalling — the label states the mechanisms are not fully known
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That in-vitro antiviral activity of a lysosomotropic drug predicts clinical benefit against a respiratory virus
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That the 6.1-fold relative risk of severe exacerbation on withdrawal is an established finding, when its confidence interval runs from 0.72 to 52.44
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That being licensed for malaria makes it a usable travel prophylaxis, when the Limitations of Use exclude every chloroquine-resistant region
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Hydroxychloroquine are recorded. Results from one form may not transfer to another.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Mechanism not reviewed
No reviewed mechanism story exists for this substance.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
What happened in people◇Read from sources, not yet reviewed
Check any of this yourself
Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.
Every line above can be traced to the study named beside it. Follow the link and read it.
Stopping it doubled the flare rate
In plain words
The trial that established hydroxychloroquine in lupus did not start it — it stopped it. Forty-seven people with stable lupus either continued or were switched to placebo. Sixteen of twenty-two on placebo flared, against nine of twenty-five who continued.
What was measured
Relative risk of clinical flare and time to flare over 24 weeks after randomised withdrawal
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
A six-month randomised double-blind placebo-controlled withdrawal study in 47 patients with clinically stable systemic lupus erythematosus assigned 25 to continue their existing hydroxychloroquine dose and 22 to placebo for 24 weeks; ten in each group were also on prednisone. The relative risk of clinical flare was 2.5 times higher on placebo (95% CI 1.08 to 5.58) — 16 of 22 against 9 of 25 — and time to flare was shorter (p=0.02). The relative risk of a severe exacerbation requiring withdrawal from the study was 6.1 times higher on placebo, but with a confidence interval spanning 0.72 to 52.44, which is not a significant finding and is frequently quoted as if it were. Prednisone dose changes did not differ between groups. A withdrawal design answers a narrower question than a start-from-scratch trial: it establishes that continuing the drug in already-stable disease prevents flares, and says nothing about what happens if you start it in active disease.
Written into the record, not signed off as a reviewed claim
The eye risk turned out to be about ten times what was taught
In plain words
For decades, hydroxychloroquine retinopathy was described as rare — well under one per cent. A 2,361-patient study using modern imaging found 7.5% overall, and close to 20% after twenty years of use. The dosing rule changed as a result.
What was measured
Prevalence of retinal toxicity by daily dose per kilogram of real body weight and by duration of use
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
A retrospective case-control study within an integrated health organisation of about 3.4 million members examined 2,361 patients who had taken hydroxychloroquine continuously for at least five years and had visual field testing or spectral-domain optical coherence tomography. Overall prevalence of retinopathy was 7.5%, varying with daily consumption (odds ratio 5.67, 95% CI 4.14 to 7.79 above 5.0 mg/kg) and duration (odds ratio 3.22, 95% CI 2.20 to 4.70 beyond 10 years). At 4.0 to 5.0 mg/kg daily, prevalence stayed under 2% in the first ten years and rose to almost 20% after twenty. Kidney disease (OR 2.08) and concurrent tamoxifen (OR 4.59, 95% CI 2.05 to 10.27) were independent risk factors. Two things changed because of this. First, the dosing basis: real body weight predicted risk better than ideal body weight, and the American Academy of Ophthalmology 2016 revision recommends a maximum of 5.0 mg/kg real weight where the previous rule used ideal weight, a change that lowers the permitted dose for most patients. Second, the screening: automated visual fields plus spectral-domain OCT annually after five years, extended to the central 24 degrees in patients of Asian descent because the damage pattern is often extramacular. The old prevalence figure was not wrong about what it measured — it measured bull’s-eye maculopathy, which is late. Better instruments found the disease earlier and the number changed by an order of magnitude.
Written into the record, not signed off as a reviewed claim
RECOVERY: no mortality benefit in COVID-19, and worse on every secondary measure
In plain words
In the largest randomised trial of the question, 1,561 hospitalised patients received hydroxychloroquine and 3,155 received usual care. Deaths at 28 days were 27.0% against 25.0%. Fewer were discharged alive, and more went on to ventilation or death.
What was measured
28-day all-cause mortality in hospitalised COVID-19
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The RECOVERY platform trial randomly assigned 1,561 patients hospitalised with COVID-19 to hydroxychloroquine and 3,155 to usual care. Enrolment into the hydroxychloroquine arm was closed on 5 June 2020 after an interim analysis found lack of efficacy. Death within 28 days occurred in 421 (27.0%) against 790 (25.0%), rate ratio 1.09 (95% CI 0.97 to 1.23, p=0.15), with consistent results in every prespecified subgroup. Patients on hydroxychloroquine were less likely to be discharged alive within 28 days (59.6% against 62.9%; rate ratio 0.90, 95% CI 0.83 to 0.98), and among those not ventilated at baseline, more progressed to invasive mechanical ventilation or death (30.7% against 26.9%; risk ratio 1.14, 95% CI 1.03 to 1.27). There was a small numerical excess of cardiac deaths of 0.4 percentage points and no difference in new major cardiac arrhythmia. The point estimates on mortality and on progression both favour usual care; only the secondary ones reach significance. The FDA revoked the emergency use authorisation on 15 June 2020, ten days after the arm closed.
Written into the record, not signed off as a reviewed claim
And it did not work as prophylaxis after exposure either
In plain words
The other version of the question — take it right after being exposed, before symptoms — was tested in 821 people and was also negative, with two and a half times as many side effects.
What was measured
Laboratory-confirmed COVID-19 or compatible illness within 14 days of a documented exposure
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
A randomised double-blind placebo-controlled trial across the United States and parts of Canada enrolled 821 asymptomatic adults within four days of a household or occupational exposure to a confirmed case at under six feet for more than ten minutes; 87.6% had high-risk exposures. New illness compatible with COVID-19 within 14 days occurred in 49 of 414 (11.8%) on hydroxychloroquine against 58 of 407 (14.3%) on placebo, an absolute difference of -2.4 percentage points (95% CI -7.0 to 2.2, p=0.35). Side effects were more common on hydroxychloroquine (40.1% against 16.8%) with no serious adverse reactions reported. Taken with RECOVERY, the two trials cover both ends of the disease course — before infection is established and after hospitalisation — and neither found benefit.
Written into the record, not signed off as a reviewed claim
The label does not claim to know how it works in lupus
In plain words
Every explanation you will read of hydroxychloroquine in lupus — endosomes, Toll-like receptors, interferon — is a hypothesis. The prescribing information states the mechanisms are not fully known.
What was measured
That hydroxychloroquine controls lupus by alkalinising endosomes and suppressing Toll-like receptor 7 and 9 signalling — a well-supported hypothesis the label declines to state as the mechanism
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Section 12.1 handles the two indications separately. For malaria it states that hydroxychloroquine is a 4-aminoquinoline antimalarial. For rheumatoid arthritis, chronic discoid lupus and systemic lupus it states: "The mechanisms underlying the anti-inflammatory and immunomodulatory effects of hydroxychloroquine sulfate tablets in the treatment of rheumatoid arthritis, chronic discoid lupus erythematosus and systemic lupus erythematosus are not fully known." The endosomal Toll-like receptor account is coherent, has laboratory support and explains why a drug that raises the pH of acidic compartments would blunt sensing of self nucleic acids. It also has a specific consequence that has not been demonstrated in patients: if that were the whole mechanism, the drug should be inert against inflammation driven through surface receptors, and its clinical profile does not obviously divide that way. This matters practically because the same uncertainty is what allowed the 2020 argument that a lysosomotropic drug would work against a respiratory virus — the mechanism was flexible enough to justify almost anything.
Source
Hydroxychloroquine sulfate tablets United States prescribing information, section 12.1
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
contested
Review state
Written into the record, not signed off as a reviewed claim
Fatal cardiomyopathy, and it is not the QT interval
In plain words
Two separate heart problems are in the label. One is a rhythm risk everyone talks about. The other is a slow accumulation of fatty material in heart muscle, found on biopsy, that can be fatal and is not detected by an ECG.
What was measured
Biopsy-confirmed phospholipidosis-associated cardiomyopathy, conduction disorders and QT prolongation
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
Section 5.1 reports fatal and life-threatening cardiotoxicity including cardiomyopathy, with signs of cardiac compromise during both acute and chronic treatment. In multiple cases, endomyocardial biopsy showed the cardiomyopathy associated with phospholipidosis in the absence of inflammation, infiltration or necrosis — the drug’s accumulation in lysosomes disrupting phospholipid handling, which is the same lysosomotropic property that is proposed to explain its benefit. Presentations include ventricular hypertrophy, pulmonary hypertension and conduction disorders including sick sinus syndrome, with atrioventricular or bundle branch block on ECG. Separately, the label records QT prolongation whose magnitude may increase with drug concentration, and ventricular arrhythmias including torsades de pointes. Sections 5.8 and 5.11 extend the phospholipidosis concern to other organs, and direct considering it as a cause of renal injury in connective tissue disease and discontinuing if it is demonstrated on biopsy in any organ system. The mechanism that makes the drug useful and the mechanism that makes it toxic are, on the label’s own account, the same physical process in different tissues.
Source
Hydroxychloroquine sulfate tablets United States prescribing information, sections 5.1, 5.8 and 5.11
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
Its malaria indication is limited by resistance the label spells out
In plain words
It is still called an antimalarial, and its label rules out most of the situations a traveller would face: it is not for complicated malaria, not where chloroquine resistance occurs, and not for preventing relapse.
What was measured
That a drug licensed for malaria treatment and prophylaxis is a usable option for travel to a malarious area — an inference its own Limitations of Use largely close off
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The Limitations of Use under section 1.1 state that hydroxychloroquine is not recommended for treatment of complicated malaria; for treatment of chloroquine- or hydroxychloroquine-resistant Plasmodium; for malaria acquired in geographic areas where chloroquine resistance occurs, or where the species has not been identified; for prophylaxis in areas where chloroquine resistance occurs; or for prevention of relapse of P. vivax or P. ovale, because it is not active against the hypnozoite liver stage — radical cure requires concomitant 8-aminoquinoline therapy. Chloroquine resistance in P. falciparum is now near-universal across sub-Saharan Africa, South and Southeast Asia and the Amazon basin, which leaves the licensed prophylaxis indication applicable to a small and shrinking fraction of the malarious world. The label directs the reader to current CDC recommendations for resistance information rather than stating a geography, which is the correct handling of a fact that changes faster than a label can.
Source
Hydroxychloroquine sulfate tablets United States prescribing information, section 1.1 Limitations of Use
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
How many documents were read
49 documents were read for this substance.
RNAWiki source record
39 of them state the same bioavailability, and they agree.
RNAWiki source record
45 of them state the same tMax, and they agree.
RNAWiki source record
Where else this substance is registered
FDA substance identifier (UNII)
8Q2869CNVH
CAS registry number
118-42-3
PubChem compound
3652
RxNorm concept
153972
Checks this page had to pass
✓ Passed
Identity resolved
no open identity hold
✓ Passed
No unresolved merge across substance families
no quarantine open
✓ Passed
Every public sentence names a source
The opening statement carries the origin: Written into the record, not signed off.
✗ Not passed
Trial roles classified for highlighted evidence
No registered study is classified as testing this substance.
✓ Passed
No internal keys in reader text
enforced by the copy-contract test over the rendered page
✗ Not passed
Safety mode resolved
No register row and no identity class settled the question.
✓ Passed
Canonical metadata present
slug and display name present
What is missing or unclear◇Read from sources, not yet reviewed
How this medicine reached us
Kept near the foot of the page. A historical event moves up only when it changes something about this substance today.
What the approval register records
17 approved applications cover products containing this substance. The earliest was NDA009768, approved 19550418 to ADVANZ PHARMA.
This order is fixed in code and does not count clicks or time on the page.
What is not here
3 questions this page could not answer
These sections were prepared and left out because there was nothing to put in them. They are listed rather than hidden, so the gaps in this record are visible.
What it may clash with — found nothing in the sources checked.
Other ways to the same goal — found nothing in the sources checked.
What changed on this page — found nothing in the sources checked.
The record as stored
The full record, for auditing
Everything above is built from what is below. This layer keeps the technical vocabulary, record identifiers and every stored row, so a reader who wants to check the page can.
The older medicine-wide conclusion held in this record
Written for a clinical reader, and about the medicine as a whole rather than about one indication, population and set of trials. RNAWiki does not treat it as a programme conclusion and no reviewer has signed it off in that form. It is here word for word because it is what the record holds.
A 4-aminoquinoline whose mechanism in lupus its own label says is not fully known, which in a 47-patient double-blind withdrawal trial produced a 2.5-fold higher relative risk of flare in those switched to placebo (95% CI 1.08 to 5.58) — and whose long-term retinal toxicity was reassessed in 2,361 patients at 7.5% overall, rising towards 20% after twenty years, about ten times the risk the field had assumed.
Recorded evidence blocks (16)
Q1
What did Hydroxychloroquine's largest trial (133553 people) and its longest (21 years) measure?
133553 people in Hydroxychloroquine's largest registered study, 21 years in its longest registered window, measuring All-cause mortality. ClinicalTrials.gov · 2026-09-01
153 phase2, 91 phase3, 63 phase1, 50 phase4, 34 na, 19 na or unstated, 9 early phase1; NCT03414502; 2029-03; no ageing endpoint recorded. Last human test completed 2026, NCT04132505.
Interpretation These counts include studies where Hydroxychloroquine was a comparison treatment, a background treatment or an exposure in an observational study, and the longest window may be a planned end date. Trial roles have not yet been classified for this record.
Show the evidence
phase2
153
phase3
91
phase1
63
phase4
50
na
34
na or unstated
19
2 more recorded rows
early phase1
9
Last recorded human testNCT04132505
2026-03-24
recorded 2026-09-01 · last checked 2026-09-04
Q2
From mouse to human: where has Hydroxychloroquine shown lifespan?
terminated; "study suspended while data is reviewed for safety and efficacy."
NCT00786682
terminated; "Lack of improved efficacy compared to historical controls, competing studies"
NCT01026844
terminated; "slow enrollment"
NCT01073852
withdrawn; "withdrawn, not funded"
14 further recorded trials
NCT01144169
terminated; "barriers to accrual: delay until surgery and additional pre-operative visits"
NCT01417403
terminated; "Recently published data that has shown HCQ to be safe when combined with chemo and or radiation at even higher doses than what is used in this study."
NCT01537315
terminated; "lack of funding"
NCT01784523
terminated; "low recruitment rate exacerbated by manufacturing shortage and price increase of hydroxychloroquine."
NCT01828476
terminated; "The Investigator left the organization."
NCT01833845
terminated; "due to failure to recruit subjects"
NCT01946880
terminated; "Slow enrollment."
NCT02026232
terminated; "COVID-19 \& loss of funding"
NCT02303405
terminated; "Investigator decision"
NCT02379650
withdrawn; "Testing required by FDA for IND approval was too expensive to move forward with conduct of the study."
NCT02414776
terminated; "PI Leaving Site"
NCT02421575
terminated; "slow accrual"
NCT02444728
terminated; "Because of insufficient enrollement"
NCT02595346
terminated; "Difficulty in enrolling new patients"
recorded 2026-09-01 · last checked 2026-09-04
Q4
Human studies of Hydroxychloroquine used Hydroxychloroquine Sulfate Tablets, 200 mg (Geneva Pharmaceutical, Inc.) — over how long?
Human studies of Hydroxychloroquine used "Hydroxychloroquine Sulfate Tablets, 200 mg (Geneva Pharmaceutical, Inc.)". ClinicalTrials.gov · 2026-09-01
Favipiravir (3200 mg + 1200 mg) combined with Hydroxychloroquine
recorded 2026-09-01 · last checked 2026-09-04
Q5
More Hydroxychloroquine was worse in human: at what point?
Hormetic in human: "Taken together, these results suggest that TP53 upregulates basal autophagy through the FBXO22-TFEB axis, which governs the hormetic effect in chemotherapy.<b>Abbreviations</b>: BBC3/PUMA: BCL2 binding component 3; CDKN1A/p21: cyclin dependent kinase inhibitor 1A; ChIP-seq: chromatin immunoprecipitation followed by…" Europe PMC · dose-response search · 2022-12-29
5 recorded sentences naming Hydroxychloroquine; hormetic, dose-response, Dose-response
Show the evidence
hormeticPMID 33706682
"Taken together, these results suggest that TP53 upregulates basal autophagy through the FBXO22-TFEB axis, which governs the hormetic effect in chemotherapy.<b>Abbreviations</b>: BBC3/PUMA: BCL2 binding component 3; CDKN1A/p21: cyclin dependent kinase inhibitor 1A; ChIP-seq: chromatin immunoprecipitation followed by sequencing; DDB2: damage specific DNA binding protein 2; DRAM: DNA damage…"
dose-responsePMID 36630735
"Based on its structure and riboswitch dose-response activity we identified that the antagonist activity of hydroxychloroquine is consistent with it being a conformationally restricted analog of the polyamine spermidine."
Dose-responsePMID 34994164
"Dose-response curves in single-molecule assays with hydroxychloroquine were created for isolates with suspected reduced susceptibility."
dose-response
PMID 34994164
"The dose-response model showed a decrease in susceptibility of these three strains to hydroxychloroquine."
PMID 12115175
"A dose-response relationship for hydroxychloroquine (HCQ), in terms of the proportion of patients achieving the Paulus 20% criteria for improvement, had previously been observed in patients with rheumatoid arthritis (RA) receiving a 6-week loading regimen of 400, 800, or 1,200 mg HCQ daily."
recorded 2022-12-29 · last checked 2026-09-04
Q6
Hydroxychloroquine's half-life is 40 to 50 days in whole blood — which schedules were studied?
40 to 50 days in whole blood, the half-life Hydroxychloroquine's label states. openfda-label · ebe00e35-ed3d-40f4-9a93-a37b0da01ddb · 2026-08-27
bioavailability 79% (SD: 12%) %.
Show the evidence
half life
40 to 50 days in whole blood; Following chronic oral administration of hydroxychloroquine, the absorption half-life of hydroxychloroquine was approximately 3 to 4 hours and the terminal half-life ranged from 40 to 50 days in whole blood.
tmax
Absorption Following a single 200 mg oral dose of hydroxychloroquine sulfate tablets to healthy male volunteers, whole blood hydroxychloroquine Cmax was 129.6 ng/mL (plasma Cmax was 50.3 ng/mL) with Tmax of 3.3 hours (plasma Tmax 3.7 hours).
bioavailability
79% (SD: 12%) %; Mean absolute oral bioavailability is 79% (SD: 12%) in fasting conditions.
metabolism
In vitro, hydroxychloroquine is metabolized mainly by CYP2C8, CYP3A4 and CYP2D6 as well as by FMO-1 and MAO-A. Elimination / Excretion Renal clearance in patients with rheumatoid arthritis treated with hydroxychloroquine sulphate tablets for at least 6 months was similar to that in single dose studies in healthy volunteers, suggesting that no change in clearance occurred with chronic dosing.
recorded 2026-08-27 · last checked 2026-09-04
Q7
Could one person measure Hydroxychloroquine's effect on progression free survival?
Progression free survival: measured in Hydroxychloroquine's trials.
Interpretation progression free survival is the recorded endpoint.
health assessment questionnaire disability index at week 12; 2026-09-01
half life
2026-09-04; halfLife; 40 to 50 days in whole blood; 2026-08-27
human trials at or under30
122
smallest human trial
0; NCT01073852; NA; the smallest recorded human enrolment at or below 30; the registry states no direction of its result; WITHDRAWN
Q8
Which of 2 month progression free survival rate, 48 week change in das28 and achieving good eular response at the end of 12 weeks did Hydroxychloroquine's trials measure?
2 month progression free survival rate, 48 week change in das28 and achieving good eular response at the end of 12 weeks lead 40 outcome terms across Hydroxychloroquine's trials. ClinicalTrials.gov · 2026-09-01
Interpretation overall survival, overall response rate, prostate specific antigen response, overall response, tumor response rate and response follow.
Show the evidence
progression free survival
1
disease activity erythrocyte sedimentation rate
1
48 week change in das28
1
overall survival
1
overall response rate
1
prostate specific antigen response
1
14 more recorded rows
overall response
1
tumor response rate
1
response
1
bioequivalence based on auc and cmax
1
that experienced a dose limiting toxicity
1
insulin sensitivity index
1
pain intensity measured by 100 mm visual analog scale
1
response rate
1
2 month progression free survival rate
1
insulin sensitivity
1
adverse events
1
dose limiting toxicity rate
1
remission
1
health assessment questionnaire disability index at week 12
1
recorded 2026-09-01 · last checked 2026-09-04
Q9
Which of Hydroxychloroquine's 50 ongoing trials reports first?
Median Progression Free Survival; Maximum tolerated dose of Akt inhibitor MK-2206; latest 2038-09-30
Show the evidence
Trial
NCT00977470
"Erlotinib With or Without Hydroxychloroquine in Chemo-Naive Advanced NSCLC and (EGFR) Mutations"; n 76; "Median Progression Free Survival"; 2027-12
NCT01480154
"Akt Inhibitor MK2206 and Hydroxychloroquine in Treating Patients With Advanced Solid Tumors, Melanoma, Prostate or Kidney Cancer"; n 62; "Maximum tolerated dose of Akt inhibitor MK-2206"; 2027-03-31
NCT02735707
"Randomized, Embedded, Multifactorial Adaptive Platform Trial for Community- Acquired Pneumonia"; n 20000; "All-cause mortality"; 2028-02
NCT03032406
"CLEVER Pilot Trial: A Phase II Pilot Trial of HydroxyChLoroquine, EVErolimus or the Combination for Prevention of Recurrent Breast Cancer"; n 53; "Feasibility: Number of Participants Who Completed 6 Cycles of Protocol Treatment Without Grade 3 or 4 Toxicity"; 2027-01-01
NCT03414502
"Treatment of Rheumatoid Arthritis With DMARDs: Predictors of Response"; n 400; "Efficacy of Disease-modifying Antirheumatic Drugs Therapy for Rheumatoid Arthritis"; 2029-03
NCT03598595
"Gemcitabine, Docetaxel, and Hydroxychloroquine in Treating Participants With Recurrent or Refractory Osteosarcoma"; n 31; "Maximum tolerated dose of hydroxychloroquine (Phase I)"; 2027-05-31
14 further recorded trials
NCT04201457
"A Trial of Dabrafenib, Trametinib and Hydroxychloroquine for Patients With Recurrent LGG or HGG With a BRAF Aberration"; n 57; "Maximum Tolerated Dose (MTD)/ Recommended Phase 2 Dose (RP2D)"; 2026-03-31
NCT04354649
"Immune-Mediated Pathophysiology And Clinical Triage Program"; n 46; "Recurrence of grade ≥2 Immune-Related Arthritis or Arthralgia"; 2029-07
NCT04381936
"Randomised Evaluation of COVID-19 Therapy"; n 70000; "Community-acquired pneumonia: All-cause mortality (with subsidiary analyses of cause of death and of death at various timepoints following discharge)"; 2038-09-30
NCT04464759
"A Study of Nivolumab and Hydroxychloroquine or Nivolumab/Ipilimumab and Hydroxychloroquine in Advanced Melanoma"; n 41; "Phase 1: Maximum tolerated dose (MTD) - Number of Subjects with Dose-limiting Toxicities"; 2027-05-12
NCT04523857
"ABemacicliB or Abemaciclib and HydroxYchloroquine to Target Minimal Residual Disease in Breast Cancer"; n 44; "Incidence of treatment-emergent adverse events during cycle 1 of the safety cohort (safety of combination HCQ + Abema)"; 2028-12
NCT04532346
"Hydroxychloroquine in Children's Interstitial Lung Diseases With Genetic Causes"; n 60; "Oxygenation status"; 2027-04
NCT04841148
"Avelumab or Hydroxychloroquine With or Without Palbociclib to Eliminate Dormant Breast Cancer"; n 96; "Determine the efficacy of HCQ or Avelumab, alone or in combination with Palbociclib, in eradicating DTCs"; 2028-05
NCT04911816
"Neoadjuvant mFOLFIRINOX With Perioperative Oral Hydroxychloroquine in Resectable Pancreatic Adenocarcinoma"; n 40; "Phase I - Establishing Maximum tolerated dose (MTD)"; 2030-06
NCT04918524
"The Clinical Features and Pregnancy Outcomes of CTD Patients"; n 126; "Live birth rate"; 2026-12-31
NCT04981145
"The Efficacy and Safety of Iguratimod (IGU) in the Treatment of Primary Sjögren's Syndrome"; n 78; "The change of SSRI-30 between the two groups at 24 weeks"; 2025-07
NCT05041907
"Finding Treatments for COVID-19: A Trial of Antiviral Pharmacodynamics in Early Symptomatic COVID-19 (PLATCOV)"; n 3800; "Rate of viral clearance for interventions relative to the no study arm (This is a superiority comparison)"; 2027-01
NCT05119140
"Administration of Hydroxychloroquine (Plaquenil) to African Americans and Hispanics for the Treatment of Mild to Severe Ulcerative Colitis"; n 3; "Change in surface CTLA4 expression"; 2025-05
NCT05126147
"Hydroxychloroquine in Mild Graves' Orbitopathy"; n 108; "The change of ophthalmic outcome"; 2026-12-31
NCT05287321
"The Efficacy of Aspirin Combined With Hydroxychloroquine Treatment in High Risk Pregnancies for Preeclampsia"; n 58; "Composite morbidity"; 2028-12-31
recorded 2026-09-01 · last checked 2026-09-04
Q10
Which running trial of Hydroxychloroquine could settle inflammatory markers?
NCT06768294 measures The evaluation the effect of baricitinib on inflammation of the synovial membrane in CPPD, reading out 2027-01.
5 open trials; n 32; "Baricitinib in CPPD - the BAPTIST Study"
Show the evidence
Trial
NCT06768294
"Baricitinib in CPPD - the BAPTIST Study"; n 32; "The evaluation the effect of baricitinib on inflammation of the synovial membrane in CPPD"; 2027-01
NCT00977470
"Erlotinib With or Without Hydroxychloroquine in Chemo-Naive Advanced NSCLC and (EGFR) Mutations"; n 76; "Median Progression Free Survival"; 2027-12
NCT02735707
"Randomized, Embedded, Multifactorial Adaptive Platform Trial for Community- Acquired Pneumonia"; n 20000; "All-cause mortality"; 2028-02
NCT05842174
"Targeting Ischemia-Induced Autophagy Dependence in Hepatocellular Carcinoma"; n 93; "Local Progression Free Survival"; 2030-10-15
NCT04381936
"Randomised Evaluation of COVID-19 Therapy"; n 70000; "Community-acquired pneumonia: All-cause mortality (with subsidiary analyses of cause of death and of death at various timepoints following discharge)"; 2038-09-30
Q11
Which 90 trials of Hydroxychloroquine posted no result?
Posted no result
90 of 90 completed trials
Registrations
NCT00946790, NCT00102557, NCT00311883, NCT00176982, NCT00873496 and NCT00031824, and 84 more
Completion dates
oldest 1993-12; newest 2024-04-11
Show the evidence
Trial
NCT00946790
1993-12
NCT00102557
2005-10
NCT00311883
2007-12
NCT00176982
2008-01
NCT00873496
2009-01
NCT00031824
2011-01
14 further recorded trials
NCT00568880
2011-06-22
NCT00632866
2012-05
NCT01396200
2012-10
NCT00962845
2013-05-30
NCT00714181
2013-06
NCT01601028
2013-08
NCT01760421
2013-08
NCT00909831
2013-11
NCT01551069
2014-04
NCT01148043
2014-09
NCT01495403
2015-04
NCT02351752
2015-10
NCT02756546
2015-12
NCT02475915
2016-03
Q12
At the median, Hydroxychloroquine's trials enrolled 57.5 people — anything larger?
Median enrolment
57.5
Largest enrolment
133553
Registered trials counted
370
Q13
What do 22165 spontaneous reports say about Hydroxychloroquine — and not say?
These are reports people sent to a regulator. They do not show the medicine caused the reaction. Nobody counted how many people took the medicine and reported nothing. The same event can be reported more than once, and many reports are incomplete. News coverage, lawsuits and new warnings change how often people report. A count is not a rate and not a risk.
Hydroxychloroquine appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 22165 reaction mentions were counted: rheumatoid arthritis 4232; drug intolerance 3086; joint swelling 2286; pain 2188. open-targets-adr · CHEMBL1535 · 2026-06-24
Show the evidence
rheumatoid arthritis
4232
drug intolerance
3086
joint swelling
2286
pain
2188
arthralgia
1902
treatment failure
1844
4 more recorded rows
synovitis
1785
fatigue
1716
condition aggravated
1612
rash
1514
recorded 2026-06-24 · last checked 2026-09-04
Q14
Hydroxychloroquine and CYP3A4, CYP1A2 and CYP2B6: shared by which compounds?
CYP3A4, CYP1A2 and CYP2B6 appear in Hydroxychloroquine's recorded interaction sentences, 16 in all. openfda-label+europepmc · 2026-08-30
In vitro, hydroxychloroquine has no significant potential to induce CYP1A2, CYP2B6 and CYP3A4.
clinical_pharmacology
In vitro, hydroxychloroquine has no significant potential to induce CYP1A2, CYP2B6 and CYP3A4. 12.4 Microbiology Mechanism of Action in Malaria The precise mechanism by which hydroxychloroquine exhibits activity against Plasmodium is not known.
pharmacokinetics
In vitro study suggested that hydroxychloroquine has no significant potential to inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, and the main transporters OATP1B1, OATP1B3, OAT1, OAT3, OCT1, and OCT2.
CYP2B6
pharmacokinetics
In vitro, hydroxychloroquine has no significant potential to induce CYP1A2, CYP2B6 and CYP3A4.
clinical_pharmacology
In vitro, hydroxychloroquine has no significant potential to induce CYP1A2, CYP2B6 and CYP3A4. 12.4 Microbiology Mechanism of Action in Malaria The precise mechanism by which hydroxychloroquine exhibits activity against Plasmodium is not known.
pharmacokinetics
In vitro study suggested that hydroxychloroquine has no significant potential to inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, and the main transporters OATP1B1, OATP1B3, OAT1, OAT3, OCT1, and OCT2.
CYP2C19pharmacokinetics
In vitro study suggested that hydroxychloroquine has no significant potential to inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, and the main transporters OATP1B1, OATP1B3, OAT1, OAT3, OCT1, and OCT2.
CYP2C8
pharmacokinetics
In vitro , hydroxychloroquine is metabolized mainly by CYP2C8, CYP3A4 and CYP2D6 as well as by FMO-1 and MAO-A Elimination/Excretion Renal clearance in patients with rheumatoid arthritis treated with hydroxychloroquine sulfate for at least 6 months was similar to that in single dose studies in healthy volunteers, suggesting that no change in clearance occurred with chronic dosing.
pharmacokinetics
In vitro study suggested that hydroxychloroquine has no significant potential to inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, and the main transporters OATP1B1, OATP1B3, OAT1, OAT3, OCT1, and OCT2.
CYP2C9pharmacokinetics
In vitro study suggested that hydroxychloroquine has no significant potential to inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, and the main transporters OATP1B1, OATP1B3, OAT1, OAT3, OCT1, and OCT2.
CYP2D6
pharmacokinetics
In vitro , hydroxychloroquine is metabolized mainly by CYP2C8, CYP3A4 and CYP2D6 as well as by FMO-1 and MAO-A Elimination/Excretion Renal clearance in patients with rheumatoid arthritis treated with hydroxychloroquine sulfate for at least 6 months was similar to that in single dose studies in healthy volunteers, suggesting that no change in clearance occurred with chronic dosing.
pharmacokinetics
Drug Interaction Studies In vitro study suggestedthat hydroxychloroquine has a potential to inhibit CYP2D6, CYP3A4, P- glycoproteins (P-gp), MATE1 and MATE2-K.
CYP3A4
pharmacokinetics
In vitro , hydroxychloroquine is metabolized mainly by CYP2C8, CYP3A4 and CYP2D6 as well as by FMO-1 and MAO-A Elimination/Excretion Renal clearance in patients with rheumatoid arthritis treated with hydroxychloroquine sulfate for at least 6 months was similar to that in single dose studies in healthy volunteers, suggesting that no change in clearance occurred with chronic dosing.
pharmacokinetics
In vitro, hydroxychloroquine has no significant potential to induce CYP1A2, CYP2B6 and CYP3A4.
clinical_pharmacology
In vitro, hydroxychloroquine has no significant potential to induce CYP1A2, CYP2B6 and CYP3A4. 12.4 Microbiology Mechanism of Action in Malaria The precise mechanism by which hydroxychloroquine exhibits activity against Plasmodium is not known.
pharmacokinetics
Drug Interaction Studies In vitro study suggestedthat hydroxychloroquine has a potential to inhibit CYP2D6, CYP3A4, P- glycoproteins (P-gp), MATE1 and MATE2-K.
recorded 2026-08-30 · last checked 2026-09-04
Q15
Was Hydroxychloroquine studied with fasting?
fasting is named in Hydroxychloroquine's label sentences: "The purpose of this trial was to evaluate the pharmacokinetics (PK), bioequivalence (BE), and safety of 2 preparations of hydroxychloroquine (200-mg tablet) under fasting and fed conditions." openfda-label+europepmc · 2026-08-30
1 recorded statement; fasting
Show the evidence
fasting
The purpose of this trial was to evaluate the pharmacokinetics (PK), bioequivalence (BE), and safety of 2 preparations of hydroxychloroquine (200-mg tablet) under fasting and fed conditions.
recorded 2026-08-30 · last checked 2026-09-04
Q16
What is recorded about Hydroxychloroquine and mTOR?
"Conversely, hydroxychloroquine, a blocker of autolysosome formation, as well as two MTOR inhibitors that activate autophagy, rapamycin and torin-1, enhanced the vesicle density." — where Hydroxychloroquine and mTOR appear together. Europe PMC · pathway abstract search · 2026-07-21
"Conversely, hydroxychloroquine, a blocker of autolysosome formation, as well as two MTOR inhibitors that activate autophagy, rapamycin and torin-1, enhanced the vesicle density."
autophagyPMID 42329081
"Conversely, hydroxychloroquine, a blocker of autolysosome formation, as well as two MTOR inhibitors that activate autophagy, rapamycin and torin-1, enhanced the vesicle density."
mTORPMID 42329081
"The density of lysosomal vesicles was increased by MTOR inhibitors and by hydroxychloroquine, but insensitive to 3-methyladenine."
autophagyPMID 42329081
"Measurements of Ca<sup>2+</sup> signals associated with contractile activation revealed that voltage-activated sarcoplasmic reticulum Ca<sup>2+</sup> release was unaffected by torin-1 but was depressed in 3-methyladenine- and in hydroxychloroquine-exposed fibers, suggesting that restraining autophagic flux is detrimental to excitation contraction coupling."
mTORPMID 42479152
"This review article summarizes and shows the effectiveness and potential of repurposed drugs including metabolic and cardiovascular modulators (metformin, simvastatin), antimicrobial and antiparasitic agents (artesunate, ivermectin, ketoconazole, chloroquine, hydroxychloroquine, niclosamide, doxycycline, pentamidine), mTOR inhibitors (temsirolimus, everolimus, rapamycin), anti-inflammatory and…"
autophagyPMID 42314534
"Furthermore, the mechanisms were investigated using the autophagy inhibitor hydroxychloroquine (HCQ), ROS scavenger N-acetylcysteine (NAC), and PI3K/AKT pathway activator Recilisib."
recorded 2026-07-21 · last checked 2026-09-04
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