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Paracetamol

  • Prescription medicine
  • Given by a clinician
  • Identity checked
  • Sources last checked 2026-09-04

This page shows what was measured, who it was measured in, and what that does not settle.

What Paracetamol does in the body

Pain and fever

Nobody knows exactly how paracetamol relieves pain, and its official prescribing information says so outright. What is reasonably established is that it acts centrally rather than at the site of injury — it resets the brain’s temperature set-point to bring a fever down, and does something to pain processing in the brain and spinal cord that has never been pinned to a specific protein. What it does not do is block inflammation in a swollen joint the way ibuprofen does, which is why it leaves the stomach, the kidney and the platelet alone, and also why it does so little for arthritis. The liver clears most of a normal dose harmlessly; a small fraction becomes a reactive molecule that is mopped up by glutathione, and when the dose outruns the glutathione supply that molecule destroys liver cells.

What happened in people

Median time to recovery from acute low back pain 17 days on paracetamol against 16 on placebo, hazard ratio 0.99 (0.87 to 1.14), in 1,652 randomised patients

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.

The limit that matters most

That paracetamol works by inhibiting prostaglandin synthesis, or by any named mechanism — the label states the site and mechanism of the analgesic effect has not been determined

Where it acts
Not established. The antipyretic action is placed at the hypothalamic heat-regulating centres; the analgesic site is unknown, with candidate mechanisms proposed in the central nervous system rather than in inflamed peripheral tissue
Kind of result
Symptoms and quality of life
Supervision
Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.

What the registries record it as

  • The substance registry classes this as chemical.

    FDA substance registry · 362O9ITL9D · read 2026-08-29

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 172 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.

Comparator

A comparator is whatever the treatment was measured against.

A picture of it, and where the picture fails

It is like the other runner in a race.

Where that stops being true. A race has one winner. A study can show both arms improved.

What people get wrong. Results are read without asking what the other group got. Beating nothing is not beating a treatment.

The control condition against which the experimental intervention is assessed.

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.

Absolute difference

An absolute difference is how many more people in a hundred were affected.

A picture of it, and where the picture fails

It is like counting heads in two rooms of a hundred.

Where that stops being true. Heads are easy to count. Study results carry a margin of error too.

What people get wrong. It is confused with a percentage change, which can look far larger.

The arithmetic difference in event rates between arms.

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.

What happened in peopleRead from sources, not yet reviewed

What happened in people

Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.

Time until recovery from acute low back pain, recovery defined as a pain score of 0 or 1 on a 0-10 scale sustained for seven consecutive days

The study did not show it

Who was studied
PACE (Lancet 2014;384:1586-1596; ACTRN12609000966291)
How many people
1652
Study design
Randomised, double-dummy, placebo-controlled, three-arm primary care trial
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
Median 17 days (95% CI 14 to 19) on regular paracetamol, 17 days (15 to 20) as-needed and 16 days (14 to 20) on placebo; hazard ratio regular against placebo 0.99 (0.87 to 1.14), adjusted p=0.79
Repeated elsewhere
Partially 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. Adherence was identical across arms (median 4.0 of a maximum 6 tablets per day in both the regular paracetamol and placebo groups), which excludes non-adherence as the explanation. Adverse events were reported by 18.5% on regular paracetamol and 18.5% on placebo.

How far it carries. This study is recorded from the curated record, not from the registry match.

Form and route. Oral tablets, caplets, chewables, oral suspensions and effervescent forms; rectal suppositories; an intravenous solution; and as a component of a very large number of combination products, prescription and over-the-counter

Interval reported. 95% CI 14 to 19) on regular paracetamol, 17 days (15 to 20) as-needed and 16 days (14 to 20) on placebo; hazard ratio regular against placebo 0

Written into the record, not signed off as a reviewed claim.

Change in mean daytime ambulatory systolic blood pressure from baseline to end of treatment, acetaminophen 1 g four times daily against placebo for two weeks

The study showed what it set out to show

Who was studied
PATH-BP (NCT01997112)
How many people
110
Study design
Randomised, double-blind, placebo-controlled crossover
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
Placebo-corrected increase of 4.7 mmHg in mean daytime systolic pressure (95% CI 2.9 to 6.6, p<0.0001) and 1.6 mmHg diastolic (0.5 to 2.7, p=0.005), in the 103 who completed both arms
Repeated elsewhere
Unreplicated

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 endpoint is a surrogate and the trial was not powered for any clinical event. It tested regular 4 g daily dosing for two weeks in people already hypertensive, and says nothing directly about occasional use.

How far it carries. This study is recorded from the curated record, not from the registry match.

Form and route. Oral tablets, caplets, chewables, oral suspensions and effervescent forms; rectal suppositories; an intravenous solution; and as a component of a very large number of combination products, prescription and over-the-counter

Interval reported. 95% CI 2

Written into the record, not signed off as a reviewed claim.

Proportion of participants achieving at least 50% of maximum pain relief over six hours

The study showed what it set out to show

Who was studied
Cochrane CD010210 — pooled single-dose ibuprofen plus paracetamol trials
How many people
1647
Study design
Systematic review of three randomised, double-blind, placebo-controlled trials
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
73% on ibuprofen 400 mg with paracetamol 1000 mg, 52% on ibuprofen 400 mg alone, 7% on placebo; number needed to treat 1.5 (95% CI 1.4 to 1.7) against placebo and 5.4 (3.5 to 12) against ibuprofen alone
Repeated elsewhere
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 models are predominantly dental extraction and the horizon is six hours. The review reports no arm of paracetamol alone against placebo at these doses, so the single-agent contribution cannot be read directly from it.

How far it carries. This study is recorded from the curated record, not from the registry match.

Form and route. Oral tablets, caplets, chewables, oral suspensions and effervescent forms; rectal suppositories; an intravenous solution; and as a component of a very large number of combination products, prescription and over-the-counter

Interval reported. 95% CI 1

Written into the record, not signed off as a reviewed claim.

What we know
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 it changes in the bodyRead 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.

  1. Start

    Paracetamol

    What a person takes: Oral tablets, caplets, chewables, oral suspensions and effervescent forms; rectal suppositories; an intravenous solution; and as a component of a very large number of combination products, prescription and over-the-counter.

    The measurement behind this step

    Absorption from the gastrointestinal tract is rapid and almost complete, and complete within four hours in overdose. Distribution is relatively uniform through most body fluids and plasma protein binding is unusually low and variable — 20% to 50% at intoxication concentrations. Metabolism is hepatic: 80 to 85% conjugated with glucuronic acid and sulfate, a minor fraction oxidised by cytochrome P450 to the reactive N-acetyl-p-benzoquinone imine.

  2. Getting in

    It is absorbed almost completely, and binds to almost nothing

    Paracetamol is absorbed quickly and near-completely from the gut, and unlike most drugs it barely sticks to blood proteins — so it spreads freely through body water, including into the brain.

    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

    The label states that absorption from the gastrointestinal tract is rapid and almost complete, that the drug is relatively uniformly distributed throughout most body fluids, and that plasma protein binding is variable, with only 20% to 50% bound at concentrations encountered during acute intoxication. Contrast ibuprofen and naproxen at above 99% bound.

  3. What it acts on

    The fever effect has an address

    For temperature, the mechanism is known: paracetamol blocks the action of the signals that tell the brain’s thermostat to raise the set-point, and the body then sheds the extra heat.

    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

    The label attributes the antipyretic effect to inhibition of endogenous pyrogen action on the hypothalamic heat-regulating centres. This is the one mechanistic claim the regulator will make for the molecule.

  4. The change it makes

    The pain effect does not

    For pain, the same document says the site and mechanism have not been determined. Several explanations are seriously proposed and none has been established.

    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

    Candidates include inhibition of cyclooxygenase in the low-peroxide environment of the central nervous system, the metabolite AM404 formed by conjugation of p-aminophenol with arachidonic acid acting at TRPV1 and CB1, and enhancement of descending serotonergic inhibition. The absence of any anti-inflammatory effect at analgesic doses is the observation every candidate has to explain.

  5. Reaching the cell

    Most of the dose leaves harmlessly

    Eighty-odd per cent of a normal dose is stuck to a sugar or a sulfate group in the liver and passed out in urine. That path has effectively unlimited capacity at ordinary doses.

    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

    About 80 to 85% is conjugated, principally with glucuronic acid and to a lesser extent with sulfate, and excreted renally. These pathways saturate only at high exposure, at which point a larger fraction is diverted to oxidation.

  6. What that does for a person

    A small fraction becomes something that destroys liver cells

    The rest is oxidised into a reactive molecule that would attack liver cells, except that a scavenger called glutathione mops it up. When the dose outruns the glutathione supply, it stops being mopped up.

    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

    Cytochrome P450, chiefly CYP2E1, oxidises a minor fraction to N-acetyl-p-benzoquinone imine, detoxified by conjugation with glutathione. Beyond the rate at which glutathione is regenerated, NAPQI forms covalent adducts with hepatocyte proteins and causes centrilobular necrosis. CYP2E1 induction by chronic alcohol and glutathione depletion by fasting or malnutrition both move the threshold downward without changing the milligram number on the box.

  7. What that does for a person

    What was measured, and where it failed

    Measured: it lowers fever, and combined with ibuprofen it is one of the most effective single-dose analgesic regimens known. Failed: acute low back pain, where it matched placebo exactly, and osteoarthritis, where the effect is smaller than anyone can feel.

    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

    PACE: median recovery 17 days on regular paracetamol against 16 on placebo, hazard ratio 0.99 (0.87 to 1.14), n=1,652. Machado meta-analysis: osteoarthritis pain -3.7 on a 0-100 scale, low back pain -0.5. Network meta-analysis of 58,451 patients: no role for single-agent paracetamol in osteoarthritis at any dose. Combination with ibuprofen 400 mg: number needed to treat 1.5 (1.4 to 1.7).

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 is missing or unclearRead 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.

  • Almost everyone, at some point, including infants and pregnant women, for whom it remains the recommended first-line antipyretic. People with liver disease, chronic alcohol use or malnutrition sit closer to the toxic threshold than the label’s milligram numbers suggest.

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 effectiveness of Acetaminophen Injection for the treatment of acute pain in pediatric patients younger than 2 years of age has not been established.”

    US prescribing information · 6d763554-913d-4bed-9efd-b9c9b936a2f4 · read 2026-08-30

  • On older people, the label states: “Of the total number of subjects in clinical studies of acetaminophen, 15% were age 65 and over, while 5% were age 75 and over.”

    US prescribing information · 6d763554-913d-4bed-9efd-b9c9b936a2f4 · read 2026-08-30

  • On people who are pregnant, the label states: “Risk Summary Published epidemiological studies with oral acetaminophen use during pregnancy have not reported a definitive association with acetaminophen use and birth defects, miscarriage, or adverse maternal or fetal outcomes [see Data ] .”

    US prescribing information · 6d763554-913d-4bed-9efd-b9c9b936a2f4 · read 2026-08-30

  • On people who are breastfeeding, the label states: “Risk Summary There is no information regarding the presence of Acetaminophen Injection in human milk, the effects on the breastfed infant, or the effects on milk production.”

    US prescribing information · 6d763554-913d-4bed-9efd-b9c9b936a2f4 · read 2026-08-30

Where the result stopped carrying

  • PACE: no difference from placebo on time to recovery from acute low back pain, with adherence identical across arms
  • The 2017 network meta-analysis of 58,451 osteoarthritis patients found no role for single-agent paracetamol at any dose
  • The blood pressure effect that was assumed not to exist was measured at 4.7 mmHg in a randomised crossover trial
  • The pregnancy neurodevelopment association reported in earlier cohorts disappeared under sibling control
  • High-quality evidence found patients on paracetamol nearly four times as likely to have abnormal liver function tests as those on placebo (risk ratio 3.8, 1.9 to 7.4), of uncertain clinical significance
  • 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 takeRead 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 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 (11)
It was studied for a different goal
The studies measured something else entirely. Nothing in this record points to this reason.
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 takeRead 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

Given by a clinician

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 tablets, caplets, chewables, oral suspensions and effervescent forms; rectal suppositories; an intravenous solution; and as a component of a very large number of combination products, prescription and over-the-counter

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

Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.

Quoted from a source

Where this came from

Copied from a source RNAWiki stored, with the source named.

Suppression classes recorded: S6.

No source is stored against this line.

What is in the pack

Absorption from the gastrointestinal tract is rapid and almost complete, and complete within four hours in overdose. Distribution is relatively uniform through most body fluids and plasma protein binding is unusually low and variable — 20% to 50% at intoxication concentrations. Metabolism is hepatic: 80 to 85% conjugated with glucuronic acid and sulfate, a minor fraction oxidised by cytochrome P450 to the reactive N-acetyl-p-benzoquinone imine.

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 and what that means for what is in the pack.

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 takeRead 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

Boxed warning for hepatotoxicity: acetaminophen has been associated with cases of acute liver failure, at times resulting in liver transplant and death, and most cases of liver injury are associated with doses exceeding 4,000 mg per day and often involve more than one acetaminophen-containing product. It has none of the NSAID gastrointestinal, renal or antiplatelet effects and does not interfere with cardioprotective aspirin. Regular 4 g daily dosing raised daytime systolic blood pressure by 4.7 mmHg in hypertensive patients. The antidote to overdose is N-acetylcysteine, which is effective in proportion to how early it is given.

Nobody counted how many people took this and were fine, so this cannot be turned into a rate.

Where this came from

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 unclearRead 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 tablets, caplets, chewables, oral suspensions and effervescent forms; rectal suppositories; an intravenous solution; and as a component of a very large number of combination products, prescription and over-the-counter

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

Distribution is relatively uniform through most body fluids and plasma protein binding is unusually low and variable — 20% to 50% at intoxication concentrations. Metabolism is hepatic: 80 to 85% conjugated with glucuronic acid and sulfate, a minor fraction oxidised by cytochrome P450 to the reactive N-acetyl-p-benzoquinone imine.

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 which forms are sold and how they compare.

No source is stored against this line.

What is recorded as being sold

  • 3870 products list this as an active ingredient in the United States drug directory. 1276 of them contain it and nothing else.

    FDA National Drug Code directory · 71335-2818 · read 2026-08-29

  • They are sold as bar, chewable, capsule, capsule, coated, capsule, gelatin coated, capsule, liquid filled and chewable gel, taken intravenous, oral, rectal and topical.

    FDA National Drug Code directory · 71335-2818 · read 2026-08-29

  • 3286 published labels name it as an active ingredient. 1059 of them describe this substance alone, which is where its own label text on this page comes from.

    US prescribing information · d4caec6d-4af2-4f1c-9add-c0c948b83b16 · read 2026-08-29

  • Those labels are classed as human otc drug and human prescription drug.

    US prescribing information · d4caec6d-4af2-4f1c-9add-c0c948b83b16 · read 2026-08-29

  • 58 marketed supplement labels list this ingredient, classed as botanical, botanical with nutrients, non-nutrient/non-botanical and other combinations.

    NIH Dietary Supplement Label Database · 214216 · read 2026-08-29

  • Those labels carry all other, nutrient and structure/function claims. A claim of that kind is written by the manufacturer and is not assessed by any regulator, so its presence says nothing about whether it is true.

    NIH Dietary Supplement Label Database · 214216 · read 2026-08-29

  • Recorded price in US: 0.01076–0.02441 USD per one millilitre, across 7 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

  • Recorded price in US: 0.02377–0.34657 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 53 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 takeRead 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.

Self-experiment planning is not offered for a prescription or clinician-supervised medicine. The questions below are for a clinician or pharmacist.

Questions worth asking

  • Which of the trials of Paracetamol 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 unclearRead 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 paracetamol works by inhibiting prostaglandin synthesis, or by any named mechanism — the label states the site and mechanism of the analgesic effect has not been determined

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 it is the appropriate first choice for low back pain or osteoarthritis, a guideline position that the randomised evidence has since reversed

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 kind to the stomach makes it cardiovascularly neutral, when 4 g daily raised systolic pressure as much as ibuprofen did

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 4,000 mg daily ceiling is a threshold rather than a population average — chronic alcohol use, fasting and liver disease move the real threshold and the label carries no personalised figure

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 unclearRead 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 Paracetamol 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 peopleRead 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.

Nobody knows how it relieves pain, and the label says so
In plain words
Paracetamol has been in use for seventy years and is taken billions of times a year. Its own prescribing information states that the site and mechanism for its analgesic effect has not been determined.
What was measured
That paracetamol is a peripheral prostaglandin inhibitor like the NSAIDs, or that any single named mechanism explains its analgesia — the label declines to name one at all
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The Clinical Pharmacology section of United States acetaminophen-containing prescribing information reads: "Acetaminophen is a non-opiate, non-salicylate analgesic and antipyretic. The site and mechanism for the analgesic effect of acetaminophen has not been determined. The antipyretic effect of acetaminophen is accomplished through the inhibition of endogenous pyrogen action on the hypothalamic heat-regulating centers." So the regulator will name a mechanism for the fever effect and will not name one for the pain effect. The candidate explanations in the literature are genuine and mutually inconsistent: inhibition of a central cyclooxygenase in a low-peroxide environment; the deacetylated metabolite recombining with arachidonic acid to form AM404, which acts at TRPV1 and cannabinoid CB1 receptors; and modulation of descending serotonergic inhibition. None has been established, and the practical consequence is not academic — a drug with no known target cannot have its dose, its interactions or its ceiling reasoned about from first principles.
Source
Acetaminophen-containing prescribing information, Clinical Pharmacology section (openFDA drug label endpoint, ANDA 202677)
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
PACE: it did not beat placebo for acute low back pain
In plain words
Paracetamol was the recommended first choice for a bad back in almost every guideline in the world. A 1,652-person randomised trial compared it with placebo and found no difference whatsoever — 17 days to recovery against 16.
What was measured
Median time to recovery from acute low back pain, paracetamol against placebo, in 1,652 randomised primary-care patients
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
PACE randomised 1,652 patients with acute low back pain across 235 primary care centres in Sydney to regular paracetamol three times daily (equivalent to 3,990 mg per day), as-needed paracetamol up to 4,000 mg per day, or placebo, all with best-evidence advice, followed for three months. Median time to recovery — defined as a pain score of 0 or 1 sustained for seven consecutive days — was 17 days (95% CI 14 to 19) in the regular group, 17 days (15 to 20) as-needed, and 16 days (14 to 20) on placebo. Hazard ratio regular against placebo 0.99 (0.87 to 1.14); adjusted p=0.79 across groups. Adherence was equivalent across arms (median 4.0 of a maximum 6 tablets per day in the regular and placebo groups alike), so this is not a compliance failure. Adverse events were reported by 18.5% on regular paracetamol and 18.5% on placebo. The authors’ own conclusion was that the findings question the universal endorsement of paracetamol in this patient group, and guidelines subsequently moved away from it.
Source
Williams CM, Maher CG, Latimer J, et al. Efficacy of paracetamol for acute low-back pain: a double-blind, randomised controlled trial. Lancet 2014;384:1586-1596
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
In osteoarthritis the effect is real, and too small to feel
In plain words
Two large syntheses reached the same place from different directions: paracetamol produces a statistically detectable improvement in arthritis pain that is below the threshold anyone can notice, and the larger of the two concluded there is no role for it in osteoarthritis at any dose.
What was measured
Weighted mean difference in pain on a 0-100 scale, and effect size against a prespecified minimum clinically important difference of -0.37
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The 2015 systematic review of 13 randomised placebo-controlled trials graded the evidence "high quality" and reported, for hip or knee osteoarthritis, a weighted mean difference in pain of -3.7 points on a 0-to-100 scale (95% CI -5.5 to -1.9) and in disability of -2.9 (-4.9 to -0.9) — statistically significant and, in the authors’ own words, not clinically important. For low back pain the corresponding figure was -0.5 (-2.9 to 1.9): nothing at all. The 2017 network meta-analysis went further, pooling 76 randomised trials with 58,451 patients across 23 treatment nodes and comparing every NSAID preparation and paracetamol dose against placebo with a prespecified minimum clinically important effect size of -0.37. Six NSAID preparations cleared it with at least 95% probability; diclofenac 150 mg daily was the best at -0.57 (95% credible interval -0.69 to -0.45). Its interpretation opens: "On the basis of the available data, we see no role for single-agent paracetamol for the treatment of patients with osteoarthritis irrespective of dose." Guideline bodies that had listed paracetamol as first-line for osteoarthritis for two decades revised that position after these analyses.
Source
Machado GC, Maher CG, Ferreira PH, et al. Efficacy and safety of paracetamol for spinal pain and osteoarthritis: systematic review and meta-analysis. BMJ 2015;350:h1225; da Costa BR, Reichenbach S, Keller N, et al. Effectiveness of non-steroidal anti-inflammatory drugs for the treatment of pain in knee and hip osteoarthritis: a network meta-analysis. Lancet 2017;390:e21-e33
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
It raises blood pressure about as much as the NSAID it is chosen to avoid
In plain words
Paracetamol is recommended over ibuprofen for people with high blood pressure on the assumption it does not affect it. A randomised crossover trial in 110 hypertensive patients found 4 g a day raised daytime systolic pressure by 4.7 mmHg.
What was measured
Placebo-corrected change in mean daytime ambulatory systolic blood pressure after two weeks of 4 g daily
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
PATH-BP was a double-blind placebo-controlled crossover trial: 110 individuals with hypertension received 1 g acetaminophen four times daily or matched placebo for two weeks, with a two-week washout before crossing over, and 24-hour ambulatory blood pressure at the start and end of each period. In the 103 who completed both arms, mean daytime systolic pressure rose from 132.8±10.5 to 136.5±10.1 mmHg on acetaminophen against 133.9±10.3 to 132.5±9.9 mmHg on placebo (p<0.0001), a placebo-corrected increase of 4.7 mmHg (95% CI 2.9 to 6.6). Daytime diastolic rose by a placebo-corrected 1.6 mmHg (0.5 to 2.7, p=0.005), with similar findings on 24-hour and clinic measurements. For comparison, ibuprofen raised 24-hour systolic pressure by 3.7 mmHg in the PRECISION-ABPM substudy. The trial’s own conclusion is that this increases cardiovascular risk and calls into question the safety of regular acetaminophen use in this situation. It studied regular 4 g daily dosing, not occasional use, and it was not powered for any clinical event.
Source
MacIntyre IM, Turtle EJ, Farrah TE, et al. Regular Acetaminophen Use and Blood Pressure in People With Hypertension: The PATH-BP Trial. Circulation 2022;145:416-423 (NCT01997112)
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
It is the leading cause of acute liver failure in the United States
In plain words
Acetaminophen accounts for 46% of all acute liver failure in the United States and between 40% and 70% in Britain and Europe — more than every prescription drug combined, several times over.
What was measured
Proportion of acute liver failure cases attributable to acetaminophen, and annual United States deaths, poison-centre calls, emergency visits and hospitalisations
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The hepatology review states: "APAP toxicity accounts for 46% of all acute liver failure (ALF) in the United States and between 40 and 70% of all cases in Great Britain and Europe", and that acetaminophen is "responsible for nearly 500 deaths annually in the U.S. alone, as well as 100,000 calls to US Poison Control Centers, 50,000 emergency room visits and 10,000 hospitalizations per year". The mechanism is well understood even though the analgesic mechanism is not: 80 to 85% of a dose is conjugated with glucuronic acid or sulfate and excreted, while a minor fraction is oxidised by cytochrome P450 to N-acetyl-p-benzoquinone imine, which is detoxified by conjugation with glutathione. When the dose exceeds the rate at which glutathione can be regenerated, the reactive metabolite binds hepatocyte proteins and centrilobular necrosis follows. The curve is flat and then vertical, which is what makes the drug feel safe right up until it is not. Two clinical phenotypes exist: intentional single-time-point overdose, and unintentional therapeutic misadventure — the person taking a therapeutic dose of several acetaminophen-containing products at once. The second is the harder to prevent and the reason for the regulatory limit.
Source
Lee WM. Acetaminophen (APAP) hepatotoxicity — Isn’t it time for APAP to go away? J Hepatol 2017;67:1324-1331
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
The pregnancy and neurodevelopment association did not survive a sibling comparison
In plain words
A run of studies reported that paracetamol in pregnancy was linked to autism and ADHD in the child. A Swedish study of 2.48 million children found the same small association — and then compared siblings within the same family, where it vanished entirely.
What was measured
Hazard ratios for autism, ADHD and intellectual disability, in a population cohort and in a matched full-sibling comparison of 2,480,797 children
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The nationwide cohort covered 2,480,797 children born in Sweden between 1995 and 2019, of whom 185,909 (7.49%) were exposed to acetaminophen in pregnancy, followed to the end of 2021. In conventional models, ever-use against no use was associated with hazard ratios of 1.05 (95% CI 1.02 to 1.08) for autism, 1.07 (1.05 to 1.10) for ADHD and 1.05 (1.00 to 1.10) for intellectual disability — small, statistically significant, and consistent with the earlier literature. The analysis then restricted to matched full sibling pairs, which holds constant everything shared within a family that a covariate list cannot capture. In that comparison the hazard ratios were 0.98 (0.93 to 1.04) for autism, 0.98 (0.94 to 1.02) for ADHD and 1.01 (0.92 to 1.10) for intellectual disability, with no dose-response pattern; for autism, low, medium and high mean daily use gave hazard ratios of 0.85, 0.96 and 0.88 against no use. The conclusion is that the associations observed in other models may have been attributable to familial confounding — the reasons a woman needs paracetamol in pregnancy, and the genetics she shares with her child, travel together. This is a conclusion shift in the direction of reassurance, and it is worth stating as clearly as the shifts that go the other way.
Source
Ahlqvist VH, Sjöqvist H, Dalman C, et al. Acetaminophen Use During Pregnancy and Children’s Risk of Autism, ADHD, and Intellectual Disability. JAMA 2024;331:1205-1214
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
It adds something real on top of an NSAID even where it does little alone
In plain words
Paracetamol alone underperforms in most of the settings it is recommended for. Combined with ibuprofen, it produced the lowest number needed to treat recorded for any single-dose analgesic comparison: 1.5.
What was measured
Proportion achieving at least 50% maximum pain relief over six hours and the derived number needed to treat, for the combination against placebo and against ibuprofen alone
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The Cochrane review of single-dose oral ibuprofen plus paracetamol for acute postoperative pain pooled three studies in 1,647 participants. At least 50% of maximum pain relief over six hours was achieved by 69% on ibuprofen 200 mg with paracetamol 500 mg, 73% on ibuprofen 400 mg with paracetamol 1000 mg, and 7% on placebo — numbers needed to treat of 1.6 (95% CI 1.5 to 1.8) and 1.5 (1.4 to 1.7). Ibuprofen 400 mg alone achieved 52%, giving a number needed to treat for the combination over ibuprofen alone of 5.4 (3.5 to 12), and the median time to rescue medication extended to 8.3 hours. So the additive effect is measured and it is modest: about one extra patient benefiting for every five treated, on top of the NSAID. That an additive effect exists is also indirect evidence that paracetamol is not acting through the same mechanism as the NSAID — which remains the most interesting unanswered question about the drug.
Source
Derry CJ, Derry S, Moore RA. Single dose oral ibuprofen plus paracetamol (acetaminophen) for acute postoperative pain. Cochrane Database Syst Rev 2013;(6):CD010210
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim

Where else this substance is registered

FDA substance identifier (UNII)
362O9ITL9D
CAS registry number
103-90-2
PubChem compound
1983
RxNorm concept
161

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

  • Passed

    Safety mode resolved

    Suppression classes recorded: S6.

  • Passed

    Canonical metadata present

    slug and display name present

What is missing or unclearRead 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.

  1. Withdrawn in United States, 2024, for "Labeling: Missing Label - some bottles are missing the the manufacturers label that includes the drug facts information." (openFDA drug enforcement Class I recall)

  2. Withdrawn in United States, 2021, for "Labeling: Label Mix-up; The bottle of over-the-counter Acetaminophen 500mg Extra Strength, 100 count, included in Health Essential Kits, labeled incorrectly with a prescription drug label instead of…" (openFDA drug enforcement Class I recall)

  3. Withdrawn in United States, 2024, for "Labeling: Label Mix-Up: Some bottles of Acetaminophen Extra Strength 500 mg tablets were incorrectly labeled with the drug facts label for Aspirin 81 mg tablets." (openFDA drug enforcement Class I recall)

  4. Withdrawn in United States, 2024, for "Labeling: Label Mix-up: a bag of Dexmedetomidine HCl in 0.9% Sodium Chloride Injection was found inside an overwrap labeled Acetaminophen Injection 1,000 mg per 100 mL (10 mg/mL)" (openFDA drug enforcement Class I recall)

  5. Withdrawn in United States, 2015, for "Labeling: Label Mix-Up; Bottles of Mucinex Fast-Max liquid are correctly labeled on the front of the label, however the back of the bottle where the Drug Facts labeling is, is missing certain Active…" (openFDA drug enforcement Class I recall)

What the approval register records

  • 535 approved applications cover products containing this substance. The earliest was NDA016401, approved 19681107 to POLYMEDICA.

    Drugs@FDA application register · NDA016401 · read 2026-08-29

  • Marketing status on the register: discontinued, none (tentative approval), over-the-counter and prescription.

    Drugs@FDA application register · NDA016401 · read 2026-08-29

  • The earliest marketing start date recorded for a listed product is 19810821.

    FDA National Drug Code directory · 71335-2818 · read 2026-08-29

What is missing or unclearRead from sources, not yet reviewed

What to learn next

Ordered by what would most change how you read this page, starting with what is easiest to misunderstand.

This order is fixed in code and does not count clicks or time on the page.

What is not here

7 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 was measured, goal by goal — found nothing in the sources checked.
  • How close this is to real life — found nothing in the sources checked.
  • Felt, measured, or meaningful — found nothing in the sources checked.
  • How long anything takes — found nothing in the sources checked.
  • 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.

The world’s most-taken analgesic, whose United States label states that the site and mechanism for its analgesic effect has not been determined, which failed to beat placebo for acute low back pain in a 1,652-patient randomised trial (median recovery 17 days against 16), produces a pain effect in osteoarthritis of -3.7 points on a 100-point scale that its own meta-analysts call not clinically important, raises daytime systolic blood pressure by 4.7 mmHg at 4 g daily in hypertensive patients, and accounts for 46% of acute liver failure in the United States.

Recorded evidence blocks (9)

On the Paracetamol label: indicated for what?


"Acetaminophen Injection is indicated for the management of mild to moderate pain in adult and pediatric patients 2 years and older the management of moderate to severe pain with adjunctive opioid analgesics in adult and pediatric patients 2 years and older the reduction of fever in adult and pediatric patients.…": indications and usage on Paracetamol's label. DailyMed label · 621282f6-75b3-401b-8e1a-c5153a0c9ecd · 2026-06-24

501 registered trials of Paracetamol — at which phases?


Registered studies posting no result
394 of 501

501 registered studies of Paracetamol: 169 phase4, 119 na, 85 phase3, 81 phase2, 52 phase1, 17 na or unstated, 5 early phase1. CLINICALTRIALS_SNAPSHOT · 2026-09-01

2137 with a PubMed record

Show the evidence
  • phase4
    169
  • na
    119
  • phase3
    85
  • phase2
    81
  • phase1
    52
  • na or unstated
    17
9 more recorded rows
  • early phase1
    5
  • completed
    360
  • unknown
    66
  • terminated
    33
  • withdrawn
    12
  • not yet recruiting
    10
  • recruiting
    10
  • active not recruiting
    8
  • suspended
    2

recorded 2026-09-01 · last checked 2026-09-04

41 of Paracetamol's trials stopped: safety, futility/efficacy, accrual/recruitment, funding/business, sponsor decision unspecified, other?


safety (2), futility/efficacy (2), accrual/recruitment (17), funding/business (3), sponsor decision unspecified (2) and other (15): Paracetamol's stop wording, clustered. CLINICALTRIALS_SNAPSHOT · 2026-09-01

"Poor recruitment and lack of funding"; 41 of 501 registered studies

Show the evidence

Trial

  • NCT00377832
    terminated; "Poor recruitment and lack of funding"
  • NCT00378547
    terminated; "ENT surgery stopped at the recruiting hospital"
  • NCT00381810
    terminated; "During a safety review of studies U2970g and U2971g, the Data Monitoring Committee recommended that enrollment in this extension trial be terminated."
  • NCT00482053
    terminated; "Low accrual"
  • NCT00681174
    terminated; "Failure to enroll sufficient patients by expected deadline."
  • NCT00855049
    withdrawn; "Unable to obtain FDA approval"
14 further recorded trials
  • NCT01019980
    terminated; "Placebo - Active Drug Not Available. No patients received drug. There are no study results to disclose."
  • NCT01104844
    withdrawn; "The study was withdrawn due to administrative reason"
  • NCT01120769
    withdrawn; "Funding issue"
  • NCT01182974
    suspended; "Difficulty in patient enrollment"
  • NCT01264965
    terminated; "recruitment problems"
  • NCT01390441
    terminated; "The study was terminated early by the Sponsor for business reasons."
  • NCT01420666
    withdrawn; "The study was withdrawn for administrative reason"
  • NCT01527942
    terminated; "Study Terminated per Principal Investigator's request"
  • NCT01530880
    terminated; "PI no longer at institution"
  • NCT01552993
    terminated; "the chosen intervention was obviously ineffective"
  • NCT01588158
    terminated; "The PI of this study is leaving the institution and enrollment was progressing slowly so we decided to close the study."
  • NCT01737593
    terminated; "Interim analysis revealed a negative effect."
  • NCT01770236
    terminated; "Study medication no longer available at institution"
  • NCT01882530
    terminated; "Practice on postoperative pain management changed"

recorded 2026-09-01 · last checked 2026-09-04

Human studies of Paracetamol used Acetaminophen 975 mg — over how long?


studies of Paracetamol used the recorded amount. ClinicalTrials.gov · 2026-09-01

20 recorded entries; human; also "Acetaminophen 975 mg", "1000 mg acetaminophen", "acetaminophen (4g/day)"

Show the evidence

human

  • NCT00377832
    Acetaminophen 975 mg
  • NCT00382083
    1000 mg acetaminophen
  • NCT00427206
    acetaminophen (4g/day)
  • NCT00508495
    Paracetamol 1% solution
  • NCT00699114
    Paracetamol (acetaminophen) 500 mg
  • NCT00699114
    Paracetamol (acetaminophen) 1000 mg
14 more recorded rows
  • human NCT00699114
    Paracetamol (acetaminophen) 1000 mg + codeine 60 mg
  • human NCT01075243
    Paracetamol 1000 mg
  • human NCT01075243
    Paracetamol 650 mg
  • human NCT01082081
    Paracetamol 500 mg
  • human NCT01448057
    Paracetamol (500 mg)/dimethindene maleate (1 mg)/ phenylephrine hydrochloride (10 mg) tablets
  • human NCT01448057
    Paracetamol (500 mg) tablets
  • human NCT01551797
    Paracetamol 750 mg
  • human NCT01606059
    Acetaminophen: 325mg
  • human NCT01756209
    acetaminophen 15 mg/kg
  • human NCT01764555
    acetaminophen 2 g
  • human NCT01938261
    Paracetamol Fresenius Kabi 10mg/ml
  • human NCT01979510
    Acetaminophen 500 mg
  • human NCT02085577
    Paracetamol 1 g
  • human NCT02113566
    Acetaminophen 1000mg

recorded 2026-09-01 · last checked 2026-09-04

Which 246 trials of Paracetamol posted no result?


Posted no result
246 of 246 completed trials
Registrations
NCT00000731, NCT00568295, NCT00000425, NCT01073670, NCT00110474 and NCT00003346, and 240 more
Completion dates
oldest 1990-05; newest 2024-08-08
Show the evidence

Trial

  • NCT00000731
    1990-05
  • NCT00568295
    2000-10
  • NCT00000425
    2001-04
  • NCT01073670
    2002-04
  • NCT00110474
    2002-12
  • NCT00003346
    2003-02
14 further recorded trials
  • NCT00240786
    2003-03
  • NCT00240773
    2003-06
  • NCT00188071
    2003-08
  • NCT00400621
    2003-09
  • NCT00371696
    2003-12
  • NCT00240825
    2004-02
  • NCT00240851
    2004-02
  • NCT00240864
    2004-02
  • NCT00261560
    2004-02
  • NCT01464944
    2004-04
  • NCT00402571
    2004-07
  • NCT00240799
    2004-10
  • NCT00763997
    2004-12
  • NCT01465009
    2005-03

At the median, Paracetamol's trials enrolled 87.5 people — anything larger?


Median enrolment
87.5
Largest enrolment
750000
Registered trials counted
498

What do 22260 spontaneous reports say about Paracetamol — 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.

Paracetamol appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 22260 reaction mentions were counted: vomiting 3638; toxicity to various agents 3281; drug hypersensitivity 2750; pain 2599. FAERS via Open Targets · CHEMBL112 · 2026-06-24

Show the evidence
  • vomiting
    3638
  • toxicity to various agents
    3281
  • drug hypersensitivity
    2750
  • pain
    2599
  • suicide attempt
    2247
  • somnolence
    1805
4 more recorded rows
  • hypersensitivity
    1578
  • hepatocellular injury
    1513
  • acute hepatic failure
    1454
  • joint swelling
    1395

recorded 2026-06-24 · last checked 2026-09-04

Which 10 reactions does Paracetamol's label not list?


acute hepatic failure, drug hypersensitivity and hepatocellular injury and 7 more reported for Paracetamol, absent from its label. FAERS via Open Targets · CHEMBL112 · 2026-06-24

2 label terms; 10 reported and unlisted; 621282f6-75b3-401b-8e1a-c5153a0c9ecd

Show the evidence
  • acute hepatic failure
    count not stated
  • drug hypersensitivity
    count not stated
  • hepatocellular injury
    count not stated
  • hypersensitivity
    count not stated
  • joint swelling
    count not stated
  • pain
    count not stated
4 more recorded rows
  • somnolence
    count not stated
  • suicide attempt
    count not stated
  • toxicity to various agents
    count not stated
  • vomiting
    count not stated

recorded 2026-06-24 · last checked 2026-09-04

Paracetamol and CYP2E1 and CYTOCHROME P450: shared by which compounds?


CYP2E1 and CYTOCHROME P450 appear in Paracetamol's recorded interaction sentences, 4 in all. DailyMed label · 621282f6-75b3-401b-8e1a-c5153a0c9ecd · 2026-06-24

CYP2E1; 1 shared nodes; drug_interactions, pharmacokinetics, clinical_pharmacology

Show the evidence

Interaction statement

  • drug_interactions
    Substances that induce or regulate hepatic cytochrome enzyme CYP2E1 may alter the metabolism of acetaminophen and increase its hepatotoxic potential.
  • drug_interactions
    ( 7.2 ) 7.1 Effects of Other Substances on Acetaminophen Substances that induce or regulate hepatic cytochrome enzyme CYP2E1 may alter the metabolism of acetaminophen and increase its hepatotoxic potential.
  • pharmacokinetics
    Elimination Metabolism Acetaminophen is primarily metabolized in the liver by first-order kinetics and involves three principal separate pathways: Conjugation with glucuronide, conjugation with sulfate, and oxidation via the cytochrome P450 enzyme pathway, primarily CYP2E1, to form a reactive intermediate metabolite (N-acetyl-p-benzoquinone imine or NAPQI).
  • clinical_pharmacology
    Elimination Metabolism Acetaminophen is primarily metabolized in the liver by first-order kinetics and involves three principal separate pathways: Conjugation with glucuronide, conjugation with sulfate, and oxidation via the cytochrome P450 enzyme pathway, primarily CYP2E1, to form a reactive intermediate metabolite (N-acetyl-p-benzoquinone imine or NAPQI).
  • CYP2E1
    FINGOLIMOD LAURYL SULFATE, FOSAPREPITANT DIMEGLUMINE, Rasagiline, Tinidazole, Naldemedine, Methylnaltrexone, Alosetron, Metaxalone

recorded 2026-06-24 · last checked 2026-09-04

Where it is registered

Where it’s registered

Withdrawn in United States, 2024, for "Labeling: Missing Label - some bottles are missing the the manufacturers label that includes the drug facts information." (openFDA drug enforcement Class I recall)

Withdrawn in United States, 2021, for "Labeling: Label Mix-up; The bottle of over-the-counter Acetaminophen 500mg Extra Strength, 100 count, included in Health Essential Kits, labeled incorrectly with a prescription drug label instead of…" (openFDA drug enforcement Class I recall)

Withdrawn in United States, 2024, for "Labeling: Label Mix-Up: Some bottles of Acetaminophen Extra Strength 500 mg tablets were incorrectly labeled with the drug facts label for Aspirin 81 mg tablets." (openFDA drug enforcement Class I recall)

Withdrawn in United States, 2024, for "Labeling: Label Mix-up: a bag of Dexmedetomidine HCl in 0.9% Sodium Chloride Injection was found inside an overwrap labeled Acetaminophen Injection 1,000 mg per 100 mL (10 mg/mL)" (openFDA drug enforcement Class I recall)

Withdrawn in United States, 2015, for "Labeling: Label Mix-Up; Bottles of Mucinex Fast-Max liquid are correctly labeled on the front of the label, however the back of the bottle where the Drug Facts labeling is, is missing certain Active…" (openFDA drug enforcement Class I recall)

Identifiers, relations and other names

The exact record

ChEMBL id
CHEMBL112
PubChem CID
1983
CAS number
103-90-2
RxCUI
161
InChIKey
RZVAJINKPMORJF-UHFFFAOYSA-N
Also called
ACETAMINOPHEN, Biocetamol
Trade name
Abdine, Acephen, Acetaminophen component of allay, Acetaminophen component of anexsia, Acetaminophen component of anoquan, Acetaminophen component of apadaz, Acetaminophen component of bancap, Acetaminophen component of bancap hc, Acetaminophen component of bucet, Acetaminophen component of butapap, Acetaminophen component of codrix, Acetaminophen component of co-gesic
Sources (7)

Sources

1 more source

ChEMBL 37 — CC BY-SA 3.0 Unported · ChEMBL ATC CC BY-SA · ClinicalTrials.gov — US Government work · Open Targets 26.06 — CC0 · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work · openFDA enforcement — US Government work

How these records are assembled · Which registers were checked

Index-quality checks
  • identity passed: no open identity hold
  • required summary fields resolved: 4 required field(s) not terminal: Why people use it, Best-supported result, Biggest unanswered question, Human evidence
  • public claims reviewed: 0 reviewed claim(s); drafts are never rendered
  • source coverage passed: 7 source rows
  • no critical contamination: no quarantine open
  • canonical metadata passed: slug and display name present
  • no raw internal fields: enforced by the copy-contract test over the rendered page

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