This page shows what was measured, who it was measured in, and what that does not settle.
What Emtricitabine does in the body
To make a DNA copy of itself, HIV has to string together building blocks in order.
Emtricitabine looks almost exactly like one of those building blocks, cytosine, but it is missing the hook the next one attaches to. Your own cells add three phosphates to it, the virus picks it up by mistake, and the chain stops there. Because the virus copies its genome without proofreading, it does not notice until it is too late.
Why people take it. HIV-1 infection, as part of a combination regimen
What happened in people
76% against 54% persistent virological response through week 60 versus stavudine in 571 treatment-naive patients (P<0.001)
✎ 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.
That non-adherence alone explains FEM-PrEP and VOICE — supported by drug levels, but the adherent subgroup was also the lower-risk subgroup in the investigators own analysis
Where it acts
Cytoplasm of CD4-positive T cells and macrophages, where the triphosphate competes with deoxycytidine triphosphate
Kind of result
The kind of result is not recorded
Supervision
RNAWiki has not recorded a supervision or regulatory status for this substance.
What the registries record it as
The substance registry classes this as chemical.
FDA substance registry · G70B4ETF4S · read 2026-08-29
Its recorded molecular formula is C8H10FN3O3S, weighing 247.24.
US prescribing information · d6599395-3944-44f9-97f2-e0424c6b6a1f · read 2026-08-30
Where each sentence above came from
A person wrote this explanation into the record, with the studies named in the path below.
The recorded use, written for a reader without medical training. Not signed off.
A limit recorded against this substance. Not signed off as a reviewed claim.
The four opening statements run to 101 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 people◇Read 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.
Probability of a persistent virological response at or below 50 copies per millilitre versus stavudine
✓ The study showed what it set out to show
Who was studied
FTC-301A (Saag, JAMA 2004)
How many people
571
Study design
Randomised, double-blind, 60-week analysis
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
P < 0.001 for 76% versus 54% through week 60
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. No limitation is recorded for this study.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral capsule and oral solution
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
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. Study drug was detected in only 22 of 43 seronegative participants tested. The headline 44% is therefore an intention-to-treat estimate over a population half of which was not taking the drug.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral capsule and oral solution
Interval reported. 95% CI 15 to 63)
Written into the record, not signed off as a reviewed claim.
Randomised, double-blind, placebo-controlled prevention trial, stopped early
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
P = 0.81; hazard ratio 0.94 (95% CI 0.59 to 1.52)
Repeated elsewhere
Failed to Replicate
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. Fewer than 40% of uninfected women in the drug arm had evidence of recent pill use. Nausea, vomiting and alanine aminotransferase elevation were all more frequent on drug.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral capsule and oral solution
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
Effectiveness -4.4% for tenofovir-emtricitabine (HR 1.04, 95% CI 0.73 to 1.49); -49.0% for oral tenofovir alone
Repeated elsewhere
Failed to Replicate
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. Tenofovir was detected in 29% of sampled plasma in the tenofovir-emtricitabine arm. Serum creatinine elevation was more frequent than on placebo (1.3% against 0.2%, P=0.004).
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral capsule and oral solution
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
RNAWiki holds 6 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 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
Emtricitabine
What a person takes: Oral capsule and oral solution.
The measurement behind this step
Taken once daily with or without food, always with at least one other antiretroviral agent. The oral solution is not interchangeable milligram for milligram with the capsule because bioavailability differs, which is a formulation fact rather than a dosing instruction.
Getting in
Swallowed once a day, and mostly ignored by the liver
A capsule taken once daily, with or without food. The body does very little to it: most of what goes in leaves unchanged in the urine.
──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
Oral bioavailability of roughly 93% for the capsule, plasma half-life around 10 hours, and about 86% recovered in urine with limited metabolism. Clearance is renal, by glomerular filtration and active tubular secretion, which is why exposure rises as kidney function falls and why it is the renal partner in every combination it belongs to.
It walks into cells and gets three phosphates added
The molecule crosses into cells easily. Once inside, the cell mistakes it for a normal building block and attaches three phosphate groups, which is exactly what turns it into a weapon.
──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
Cellular enzymes phosphorylate emtricitabine to emtricitabine 5-prime-triphosphate, the species the label names as the active one. The triphosphate persists inside the cell for considerably longer than the roughly 10-hour plasma half-life of the parent, which is why once-daily dosing works and why a plasma concentration is a poor guide to activity.
Reverse transcriptase picks it up instead of the real thing
HIV is in the middle of copying its RNA into DNA. It needs a cytosine block, and the fake one is sitting right there looking correct.
╌╌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
Emtricitabine triphosphate competes with deoxycytidine triphosphate at the polymerase active site of HIV-1 reverse transcriptase. Selectivity is high: the label records it as a weak inhibitor of mammalian DNA polymerases alpha, beta and epsilon and of mitochondrial polymerase gamma, which is the structural reason this class replaced the D-configuration nucleosides whose mitochondrial toxicity produced lipoatrophy and neuropathy.
The chain stops, because there is no hook for the next block
A normal building block has an attachment point for the next one. This one has a sulfur ring where that point should be, so the copy ends there and cannot be resumed.
╌╌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 3-prime position of the 1,3-oxathiolane ring carries no hydroxyl, so no phosphodiester bond can be formed to the next incoming nucleotide and DNA synthesis terminates obligately. Unlike the thymidine analogues, emtricitabine-terminated chains are poorly excised by the pyrophosphorolysis reaction that thymidine-analogue mutations enhance, which is why this drug is not compromised by that resistance pathway.
Without a complete DNA copy there is nothing to paste into the chromosome. The virus that entered that cell reaches a dead end, and the same happens in the next cell, and the plasma level falls.
╌╌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
Incomplete reverse transcripts are degraded and no integration-competent DNA is produced. In prophylaxis the same chemistry is used pre-emptively: the triphosphate is loaded into mucosal and circulating target cells before exposure, which is why the effect depends on the intracellular concentration at the moment of exposure and why drug-level data, not pill counts, explain the difference between the trials that worked and the trials that did not.
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 5 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 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.
People living with HIV-1 on a combination regimen, and HIV-negative people taking a fixed-dose combination for pre-exposure prophylaxis. It is on the WHO Model List of Essential Medicines.
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 pharmacokinetics of FTC were studied in 20 neonates born to HIV-1 positive mothers [see Clinical Studies (14.4) ] .”
US prescribing information · d6599395-3944-44f9-97f2-e0424c6b6a1f · read 2026-08-30
On older people, the label states: “Clinical trials of EMTRIVA did not include sufficient numbers of subjects aged 65 years and over to determine whether they respond differently from younger subjects.”
US prescribing information · d6599395-3944-44f9-97f2-e0424c6b6a1f · read 2026-08-30
On people who are pregnant, the label states: “Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to EMTRIVA during pregnancy.”
US prescribing information · d6599395-3944-44f9-97f2-e0424c6b6a1f · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary The Centers for Disease Control and Prevention recommend that HIV-1 infected mothers not breastfeed their infants to avoid risking postnatal transmission of HIV-1.”
US prescribing information · d6599395-3944-44f9-97f2-e0424c6b6a1f · read 2026-08-30
On people with reduced kidney function, the label states: “Modify the dose or dosing interval for EMTRIVA in patients with creatinine clearance below 50 mL/min or in patients with end stage renal disease requiring dialysis [see Dosage and Administration (2.6) ] .”
US prescribing information · d6599395-3944-44f9-97f2-e0424c6b6a1f · read 2026-08-30
Where the result stopped carrying
FEM-PrEP was stopped early on 18 April 2011 for lack of efficacy after 33 infections on drug against 35 on placebo
VOICE found a point estimate favouring placebo in the oral tenofovir arm and no effect in the tenofovir-emtricitabine arm
M184V arises quickly on failure and abolishes activity, so the drug protects only while the regimen around it is working
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 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 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 capsule and oral solution
✎ 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
Taken once daily with or without food, always with at least one other antiretroviral agent. The oral solution is not interchangeable milligram for milligram with the capsule because bioavailability differs, which is a formulation fact rather than a dosing instruction.
✎ 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 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
The label carries a boxed warning for post-treatment acute exacerbation of hepatitis B in patients coinfected with HIV-1 and HBV who stop the drug. Lactic acidosis and severe hepatomegaly with steatosis are labelled as a nucleoside-analogue class warning. Skin hyperpigmentation of the palms and soles is characteristic and benign. Renal clearance means exposure rises with declining kidney function. Emtricitabine has no established mitochondrial toxicity of the kind that made stavudine and zalcitabine unusable.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
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 capsule and oral solution
✎ 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
The oral solution is not interchangeable milligram for milligram with the capsule because bioavailability differs, which is a formulation fact rather than a dosing instruction.
✎ 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
120 products list this as an active ingredient in the United States drug directory. 24 of them contain it and nothing else.
FDA National Drug Code directory · 47234-2501 · read 2026-08-29
They are sold as capsule, powder, solution, tablet and tablet, film coated, taken oral.
FDA National Drug Code directory · 47234-2501 · read 2026-08-29
The regulator's established pharmacologic class for it is human immunodeficiency virus nucleoside analog reverse transcriptase inhibitor [epc], nucleoside reverse transcriptase inhibitors [moa] and nucleosides [cs].
FDA National Drug Code directory · 47234-2501 · read 2026-08-29
55 published labels name it as an active ingredient. 3 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · 54e82b13-a037-49ed-b4b3-030b37c0ecdd · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · 54e82b13-a037-49ed-b4b3-030b37c0ecdd · read 2026-08-29
Emtriva is oral at 3 DOSAGE FORMS AND STRENGTHS EMTRIVA is available as capsules or as an oral solution. 200 mg Capsules: 200 mg of emtricitabine (FTC): size 1 hard gelatin capsules with a blue cap and white body, printed with "200 mg" in…, recorded as fda label in effect 2025-12-02 in the United States.
US prescribing information · d6599395-3944-44f9-97f2-e0424c6b6a1f · read 2026-08-30
Recorded price in US: 12.48626 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 2 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 Emtricitabine 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 non-adherence alone explains FEM-PrEP and VOICE — supported by drug levels, but the adherent subgroup was also the lower-risk subgroup in the investigators own analysis
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 emtricitabine and lamivudine are interchangeable in every regimen — only three of twelve pooled trials compared them directly
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 emtricitabine has an effect of its own inside a fixed-dose combination that can be separated from its partners; outside FTC-301A and FTC-303 it has never been the variable
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 Emtricitabine 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.
FTC-301A: 76% against 54% persistent suppression at 60 weeks versus stavudine
In plain words
In the one trial where emtricitabine was the variable being tested, 571 previously untreated patients got either it or stavudine on the same background. Emtricitabine held the virus down in 76% through 60 weeks against 54%, and fewer people stopped it for side effects.
What was measured
Probability of persistent virological response at or below 50 copies per millilitre through week 60
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Saag and colleagues randomised 571 antiretroviral-naive adults with HIV-1 RNA of at least 5,000 copies per millilitre at 101 sites to once-daily emtricitabine 200 mg (n=286) or twice-daily stavudine (n=285), each with didanosine and efavirenz. At the 42-week interim analysis the probability of a persistent virological response at or below 50 copies per millilitre was 85% against 76% (P=0.005), with mean CD4 increases of 156 against 119 cells per microlitre (P=0.01). Through week 60 the persistent response was 76% against 54% (P<0.001), virological failure 4% against 12% (P<0.001), and discontinuation for adverse events 7% against 15% (P=0.005).
Written into the record, not signed off as a reviewed claim
Study 934: the tenofovir-emtricitabine backbone beat zidovudine-lamivudine
In plain words
The trial that made the Truvada backbone standard. In 517 previously untreated patients, tenofovir with emtricitabine suppressed more virus than zidovudine with lamivudine and caused less than half as many discontinuations.
What was measured
Proportion below 400 and below 50 copies per millilitre at week 48, and discontinuations for adverse events
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Gallant and colleagues ran an open-label noninferiority study in 517 treatment-naive patients randomised to once-daily tenofovir disoproxil, emtricitabine and efavirenz or to twice-daily fixed-dose zidovudine-lamivudine plus efavirenz. Through week 48, 84% against 73% reached HIV-1 RNA below 400 copies per millilitre (95% CI for the difference 4 to 19, P=0.002), and 80% against 70% reached below 50 copies per millilitre (95% CI 2 to 17, P=0.02). Mean CD4 increases were 190 against 158 cells per cubic millimetre (95% CI 9 to 55, P=0.002). Adverse events causing discontinuation were 4% against 9% (P=0.02). The K65R mutation developed in no patient in either arm.
Written into the record, not signed off as a reviewed claim
Prevention works when the drug is actually in the blood: 75% in Partners PrEP
In plain words
In 4,747 couples where one partner had HIV and one did not, daily tenofovir with emtricitabine cut new infections in the HIV-negative partner by three quarters. In a similar trial in men who have sex with men the reduction was 44%, and the drug was detectable in only half the people who were supposed to be taking it.
What was measured
HIV-1 incidence per 100 person-years and relative risk reduction
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Partners PrEP (NCT00557245) enrolled 4,747 HIV-1 serodiscordant heterosexual couples in Kenya and Uganda. Incidence in the HIV-negative partner was 1.99 per 100 person-years on placebo (52 infections), 0.65 on tenofovir disoproxil (17 infections, 67% relative reduction, 95% CI 44 to 81, P<0.001) and 0.50 on tenofovir-emtricitabine (13 infections, 75% relative reduction, 95% CI 55 to 87, P<0.001). iPrEx (NCT00458393) randomised 2,499 HIV-seronegative men and transgender women who have sex with men and found 36 infections on tenofovir-emtricitabine against 64 on placebo, a 44% reduction (95% CI 15 to 63, P=0.005); study drug was detected in 22 of 43 seronegative participants tested (51%) and in 3 of 34 who became infected (9%), P<0.001.
Written into the record, not signed off as a reviewed claim
FEM-PrEP and VOICE: two large trials in African women found no effect at all
In plain words
Two trials enrolling more than 7,000 African women between them found that daily tenofovir with emtricitabine prevented nothing. In both, drug was detectable in fewer than a third of the women who were assigned to take it. The trials measured the pills prescribed, not the pills swallowed.
What was measured
Hazard ratio for HIV-1 acquisition, and proportion of plasma samples with detectable tenofovir
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
FEM-PrEP (NCT00625404) randomised 2,120 HIV-negative women in Kenya, South Africa and Tanzania to daily tenofovir-emtricitabine or placebo. Infections occurred in 33 women on drug (4.7 per 100 person-years) and 35 on placebo (5.0 per 100 person-years), hazard ratio 0.94 (95% CI 0.59 to 1.52, P=0.81). Fewer than 40% of uninfected women in the drug arm had evidence of recent pill use at matched visits. The trial was stopped early on 18 April 2011 for lack of efficacy. VOICE (NCT00705679) enrolled 5,029 women in South Africa, Uganda and Zimbabwe across oral tenofovir, oral tenofovir-emtricitabine and vaginal tenofovir gel arms; 312 infections occurred at 5.7 per 100 person-years, and effectiveness was -49.0% for tenofovir (HR 1.49, 95% CI 0.97 to 2.29), -4.4% for tenofovir-emtricitabine (HR 1.04, 95% CI 0.73 to 1.49) and 14.5% for the gel. Tenofovir was detected in 30%, 29% and 25% of sampled plasma. Creatinine elevation was more frequent on oral tenofovir-emtricitabine than placebo, 1.3% against 0.2% (P=0.004).
Written into the record, not signed off as a reviewed claim
The adherence explanation for the failed trials is an inference, not a randomisation
In plain words
Everyone now says FEM-PrEP and VOICE failed because the women did not take the tablets. The drug-level measurements strongly support that. But nobody randomised anyone to adherence, so the alternative explanations were never excluded by design.
What was measured
That non-adherence is the sole reason oral tenofovir-emtricitabine prophylaxis failed in African women — supported by drug levels, established by no randomisation
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The adherence account rests on an association within the trials: participants with detectable plasma tenofovir were less likely to seroconvert. In VOICE the investigators themselves report that detection of tenofovir in plasma was negatively associated with the characteristics that predict HIV-1 acquisition, which means the adherent subgroup was also the lower-risk subgroup and the comparison between them is confounded by the same behaviour it is meant to explain. Competing hypotheses that the same data cannot exclude include lower genital-tract tenofovir concentrations in women than in rectal tissue, and a higher force of infection in the enrolled populations. The correct statement is that these trials measured what happens when a prescription is issued, and that the drug-level data are consistent with non-use being the main reason no effect appeared.
Written into the record, not signed off as a reviewed claim
Interchangeability with lamivudine is a pooled estimate, not three big head-to-heads
In plain words
Emtricitabine and lamivudine are treated as the same drug in practice. A systematic review supports that, but most of the evidence comes from comparing trials with each other rather than from randomising patients between the two.
What was measured
That emtricitabine and lamivudine are clinically identical in every regimen — a conclusion resting mainly on indirect comparison
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Ford and colleagues pooled 12 trials contributing 15 randomised comparisons in 4,913 patients. Across all trials the relative risk for treatment success was 1.00 (95% CI 0.97 to 1.02) and for treatment failure 1.08 (95% CI 0.94 to 1.22). Only three of the twelve trials compared lamivudine and emtricitabine directly; in that subset the relative risk for success was 1.03 (95% CI 0.96 to 1.10). The direct estimate is compatible with equivalence and also compatible with a 4% advantage in either direction, and it is the estimate carrying the interchangeability claim, because the remaining comparisons differ in more than one component.
Written into the record, not signed off as a reviewed claim
M184V ends the drug within weeks, and the label carries a hepatitis B boxed warning
In plain words
A single mutation at position 184 makes emtricitabine stop working, and it appears quickly once a regimen starts to fail. Separately, the drug also suppresses hepatitis B, so stopping it in someone who has both infections can trigger a severe liver flare.
What was measured
Presence of the M184V substitution at virological failure, and the labelled boxed warning for hepatitis B exacerbation on discontinuation
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The M184V substitution in HIV-1 reverse transcriptase confers high-level resistance to emtricitabine and to lamivudine, and is the characteristic mutation selected on failure of either. The FDA-approved label for EMTRIVA carries a boxed warning for post-treatment acute exacerbation of hepatitis B: emtricitabine is active against hepatitis B virus, patients coinfected with HIV-1 and HBV who discontinue it may experience severe acute exacerbations of hepatitis, and hepatic function requires close monitoring for at least several months after stopping. Emtricitabine is not approved for the treatment of chronic hepatitis B, so this is a drug with hepatitis B activity, a hepatitis B withdrawal warning, and no hepatitis B indication.
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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.
A fluorinated cytidine analogue that is chopped into the growing viral DNA chain and stops it dead; it beat stavudine on suppression at 60 weeks (76% against 54%) in its own registration trial, and in prevention it cut HIV acquisition by 75% where people took it and by nothing at all in the two trials where they did not.
Recorded evidence blocks (10)
Q1
On the Emtricitabine label: indicated for what?
"Emtricitabine is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection. Emtricitabine, a nucleoside analog HIV-1 reverse transcriptase inhibitor, is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection.": indications and usage on Emtricitabine's label. DailyMed label · a229c922-58eb-4795-9219-6cebb1779e35 · 2026-08-18
Q2
99 registered trials of Emtricitabine — at which phases?
Registered studies posting no result
56 of 99
99 registered studies of Emtricitabine: 31 phase3, 25 phase2, 18 phase4, 15 phase1, 9 na, 8 na or unstated. CLINICALTRIALS_SNAPSHOT · 2026-09-01
futility/efficacy (1), accrual/recruitment (4), sponsor decision unspecified (1) and other (1): Emtricitabine's stop wording, clustered. CLINICALTRIALS_SNAPSHOT · 2026-09-01
"study was withdrawn before any participants were recruited and enrolled"; 7 of 99 registered studies
Show the evidence
Trial
NCT00087464
withdrawn; "study was withdrawn before any participants were recruited and enrolled"
NCT01338025
terminated; "Study was halted for lack of accrual"
NCT01614405
terminated; "Protracted gastrointestinal symptoms were experienced by most patients who were subsequently found to be in the treatment arm on LPV/r. This observation resulted in cessation of enrolment and a decision not to continue the RCT"
NCT02116660
terminated; "This study was terminated early due to poor recruitment."
NCT03304717
withdrawn; "Results from other clinical trials on AGS established baricitinib as standard of care treatment. Thanks to the knowledge gained in the clinical treatment of AGS, a clinical trial around the effects of RTI in AGS is no longer relevant at…"
NCT03493568
terminated; "The futility analysis on 24-week results estimated that there was only 2% probability of verifying the study hypothesis of a higher proportion pat. with no residual viremia through 48w in arm E/C/F/TAF"
1 further recorded trialNCT03877536
withdrawn; "Feeder cohort study closed."
recorded 2026-09-01 · last checked 2026-09-04
Q4
Human studies of Emtricitabine used FDC Emtricitabine 200 mg/ tenofovir 300 mg — over how long?
Human studies of Emtricitabine used "FDC Emtricitabine 200 mg/ tenofovir 300 mg". ClinicalTrials.gov · 2026-09-01
7 recorded entries; human; also "FDC Emtricitabine 200mg/Tenofovir 300mg DF/Efavirenz 600mg", "Emtricitabine 200 MG", "Genvoya 150Mg-150Mg-200Mg-10Mg Tablet"
10 hours; Elimination The plasma FTC half-life is approximately 10 hours.
tmaxpharmacokinetics
1-2 hours; Figure 1 Mean (± 95% CI) Steady-State Plasma FTC Concentrations in HIV-1-Infected Adults (N=20) Absorption Emtricitabine is rapidly and extensively absorbed following oral administration, with peak plasma concentrations occurring at 1-2 hours postdose.
bioavailabilitypharmacokinetics
93 %; The mean absolute bioavailability of emtricitabine capsules was 93%, while the mean absolute bioavailability of emtricitabine oral solution was 75%.
metabolismpharmacokinetics
Metabolism Following administration of radiolabelled FTC, complete recovery of the dose was achieved in urine (~86%) and feces (~14%).
recorded 2026-08-18 · last checked 2026-09-04
Q6
Which 27 trials of Emtricitabine posted no result?
Posted no result
27 of 27 completed trials
Registrations
NCT00642291, NCT00006144, NCT00036452, NCT00127959, NCT00158457 and NCT00106379, and 21 more
Completion dates
oldest 2004-07; newest 2024-02-15
Show the evidence
Trial
NCT00642291
2004-07
NCT00006144
2005-04
NCT00036452
2006-01
NCT00127959
2006-08
NCT00158457
2006-12
NCT00106379
2007-01
14 further recorded trials
NCT00102206
2007-05
NCT00051831
2008-05
NCT00476463
2008-12
NCT00380159
2009-01
NCT00115609
2009-11
NCT00334256
2009-12
NCT01040091
2014-04
NCT01637233
2015-12
NCT01637259
2015-12
NCT02157311
2016-01
NCT02475915
2016-03
NCT01571128
2016-03-23
NCT02984852
2017-02
NCT03092206
2017-07-28
Q7
At the median, Emtricitabine's trials enrolled 72 people — anything larger?
Median enrolment
72
Largest enrolment
2000
Registered trials counted
97
Q8
What do 2906 spontaneous reports say about Emtricitabine — 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.
Emtricitabine appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 2906 reaction mentions were counted: drug resistance 447; virologic failure 384; abortion spontaneous 359; immune reconstitution inflammatory syndrome 311. FAERS via Open Targets · CHEMBL885 · 2026-06-24
Show the evidence
drug resistance
447
virologic failure
384
abortion spontaneous
359
immune reconstitution inflammatory syndrome
311
blood creatinine increased
305
osteoporosis
250
4 more recorded rows
premature baby
249
viral load increased
234
blood hiv rna increased
192
product dispensing error
175
recorded 2026-06-24 · last checked 2026-09-04
Q9
Which 10 reactions does Emtricitabine's label not list?
Assessment of Drug Interactions At concentrations up to 14-fold higher than those observed in vivo , FTC did not inhibit in vitro drug metabolism mediated by any of the following human CYP isoforms: CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, and CYP3A4.
clinical_pharmacology
Assessment of Drug Interactions At concentrations up to 14-fold higher than those observed in vivo , FTC did not inhibit in vitro drug metabolism mediated by any of the following human CYP isoforms: CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, and CYP3A4.
Emtricitabine component of atripla, Emtricitabine component of biktarvy, Emtricitabine component of complera, Emtricitabine component of descovy, Emtricitabine component of eviplera, Emtricitabine component of genvoya, Emtricitabine component of odefsey, Emtricitabine component of stribild, Emtricitabine component of symtuza, Emtricitabine component of truvada, Emtriva, Emtricitabine/Tenofovir disoproxil Mylan
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
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✓ source coverage passed: 6 source rows
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