This page shows what was measured, who it was measured in, and what that does not settle.
What Ribavirin does in the body
Ribavirin looks enough like guanosine, one of the four building blocks of RNA, that cells and viruses both pick it up and phosphorylate it.
After that the story becomes genuinely unsettled: it can starve the cell of real guanosine, it can be inserted into viral genomes and cause so many copying errors that the virus mutates itself to death, it can interfere with the cap a virus puts on its messages, it can slow the copying enzyme directly, and it shifts the immune response. Five mechanisms have been proposed and evidence exists for each; which one matters in a given infection is still argued. What is not in doubt is the side effect: the phosphorylated drug builds up inside red blood cells, which cannot remove it, and they break apart.
Why people take it. An older antiviral now used mainly as an add-on for hepatitis C.
What happened in people
Adding it roughly tripled hepatitis C cure with older interferon treatment and improved later interferon combinations.
✓ Reviewed first-read answer
Where this came from
A person wrote this and a reviewer approved it against this exact record. It carries no effect size.
A reviewer approved this against this record. The reviewed-claim record carrying the exact population and effect size does not exist yet.
No source is stored against this line.
The limit that matters most
Five biological explanations exist, and none has been established.
Where it acts
Everywhere the nucleoside transporters reach — hepatocyte cytoplasm for the antiviral effect, and the red blood cell, where the phosphorylated drug accumulates and causes the toxicity
Kind of result
The kind of result is not recorded
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 · 49717AWG6K · read 2026-08-29
Where each sentence above came from
A person wrote this explanation into the record, with the studies named in the path below.
A reviewer approved this sentence against this exact record and its sources.
The limit a reviewer approved as the one that matters most here.
The four opening statements run to 158 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.
Hepatitis Interventional Therapy Group (McHutchison 1998, N Engl J Med)
How many people
912
Study design
Phase 3, randomised, interferon alfa-2b with or without ribavirin
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
38% (87/228) at 48 weeks and 31% (70/228) at 24 weeks with ribavirin, against 13% (29/225) and 6% (13/231) without; P<0.001
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. Dose reduction and discontinuation were more frequent with ribavirin, and the paper does not resolve how much of the added benefit was offset by the added toxicity.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, capsule and solution; separately, an inhalation solution given by small-particle aerosol
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Sustained virologic response, undetectable HCV RNA 24 weeks after cessation of therapy
✓ The study showed what it set out to show
Who was studied
Fried 2002, N Engl J Med — peginterferon alfa-2a with ribavirin or placebo
How many people
1121
Study design
Phase 3, randomised, three-arm, with a matching placebo arm
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
56% with peginterferon plus ribavirin against 29% with peginterferon plus placebo and 44% with interferon alfa-2b plus ribavirin; P<0.001 for both comparisons
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 tablet, capsule and solution; separately, an inhalation solution given by small-particle aerosol
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Mortality in infants with RSV lower respiratory tract infection
✗ The study did not show it
Who was studied
Cochrane CD000181 — aerosolised ribavirin for RSV in infants
How many people
158
Study design
Systematic review of 12 randomised placebo-controlled trials
Compared against
A dummy treatment
Kind of result
Living longer, or avoiding a major event
What was found
Mortality 5.8% against 9.7%, odds ratio 0.58 (95% CI 0.18 to 1.85) across four trials with 158 participants — the confidence interval crosses 1
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. The reviewers state the trials lack sufficient power to provide reliable estimates. Occupational exposure of ward staff to aerosolised ribavirin, a known teratogen, is a documented concern that the efficacy trials were not designed to quantify.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, capsule and solution; separately, an inhalation solution given by small-particle aerosol
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
Mortality with ribavirin against no ribavirin in Lassa fever
✗ The study did not show it
Who was studied
Cheng 2022, Emerg Infect Dis — ribavirin for Lassa fever
How many people
13
Study design
Systematic review of 13 published and unpublished comparative studies
Compared against
Not recorded for this study
Kind of result
Living longer, or avoiding a major event
What was found
Ribavirin was associated with decreased mortality, but every one of the 13 studies was at critical or serious risk of bias on ROBINS-I, so no pooled estimate was considered reliable
Repeated elsewhere
Unreplicated
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. Unpublished data from a Sierra Leone study had to be obtained through a Freedom of Information Act request. Uncontrolled confounding, immortal time bias and missing outcome data were the recurring problems.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, capsule and solution; separately, an inhalation solution given by small-particle aerosol
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
RNAWiki holds 4 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
Ribavirin
What a person takes: Oral tablet, capsule and solution; separately, an inhalation solution given by small-particle aerosol.
The measurement behind this step
The oral forms are used in hepatitis C in combination with peginterferon or with certain direct-acting antiviral regimens. The inhalation solution is a distinct product for hospitalised infants and young children with severe RSV lower respiratory tract infection and is not indicated in adults.
Getting in
Taken as a tablet, or breathed in as a mist
Two completely different products share the same molecule: an oral tablet or capsule used in hepatitis C, and an aerosol given to hospitalised infants with RSV.
──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 ribavirin is well absorbed and widely distributed, with a multiple-dose half-life of 12 days and persistence in non-plasma compartments for up to six months. The inhalation solution is delivered by small-particle aerosol generator and carries separate warnings about drug precipitate obstructing mechanical ventilators.
Carried into cells by the transporters meant for real nucleosides
Because it looks like guanosine, the cell’s own nucleoside doorways let it in. Red blood cells let it in too, and that is where the trouble starts.
╌╌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
Uptake is via equilibrative nucleoside transporters, principally ENT1. Intracellular kinases phosphorylate it to the mono-, di- and triphosphate. Erythrocytes phosphorylate it but lack the phosphatase to reverse the reaction, so the triphosphate accumulates and causes dose-dependent hemolysis.
Five things it could be doing, and nobody has settled which
It can starve the cell of real guanosine, get inserted into viral genomes and cause copying errors, interfere with the cap a virus puts on its messages, slow the copying enzyme directly, or shift the immune response. Evidence exists for all five.
╌╌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
Proposed mechanisms: inhibition of inosine monophosphate dehydrogenase depleting the GTP pool; lethal mutagenesis, since ribavirin triphosphate templates cytidine and uridine with equal efficiency; interference with RNA capping; direct RNA-dependent RNA polymerase inhibition; and immunomodulation. Distinct virus and host combinations may favour different mechanisms.
In hepatitis C the visible effect is on relapse, not on viral load
Ribavirin alone barely changes the amount of virus in the blood. What it changes is how many people relapse after interferon stops, which is why it only ever worked as a partner.
╌╌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’s own boxed warning states that ribavirin monotherapy is not effective for chronic hepatitis C. Its measurable contribution appears as a difference in sustained response rather than in on-treatment viral kinetics, which is one of the reasons the mechanism has resisted identification in this disease.
With interferon alone, roughly one in eight people were cured. Adding ribavirin took that to roughly two in five, and adding it to peginterferon took 29% to 56%.
──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
SVR was 38% against 13% at 48 weeks in 912 randomised patients on interferon alfa-2b, and 56% against 29% in 1,121 randomised patients on peginterferon alfa-2a with matching placebo. In genotype 1 the peginterferon figures were 46% against 21%.
The price was anemia, teratogenicity and a long tail
Red cells break apart, and in people with heart disease the anemia has caused fatal heart attacks. It also damages developing embryos in every animal species tested and lingers in the body for months after the last dose.
──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
Three boxed warnings: embryo-fetal toxicity, hemolytic anemia leading to fatal and non-fatal myocardial infarction, and monotherapy not recommended. Contraception is required for nine months after treatment in female patients and six months in the female partners of male patients.
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 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.
In hepatitis C, patients aged 5 and over on a combination regimen — a role that has shrunk close to nothing since 2014. As an aerosol, hospitalised infants with severe RSV. Never anyone who is pregnant, whose partner is pregnant, or who has significant cardiac disease.
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: “Safety and effectiveness of ribavirin have not been established in patients below the age of 5 years.”
US prescribing information · eee304d0-c2ea-44f4-97d9-92a414d31b6c · read 2026-08-30
On older people, the label states: “Clinical studies of ribavirin and PEGASYS ® did not include sufficient numbers of subjects aged 65 or over to determine whether they respond differently from younger subjects.”
US prescribing information · eee304d0-c2ea-44f4-97d9-92a414d31b6c · read 2026-08-30
On people who are pregnant, the label states: “Category X [see Contraindications (4) ] .”
US prescribing information · eee304d0-c2ea-44f4-97d9-92a414d31b6c · read 2026-08-30
On people who are breastfeeding, the label states: “It is not known whether ribavirin is excreted in human milk.”
US prescribing information · eee304d0-c2ea-44f4-97d9-92a414d31b6c · read 2026-08-30
On people with reduced liver function, the label states: “The effect of hepatic impairment on the pharmacokinetics of ribavirin following administration of ribavirin has not been evaluated.”
US prescribing information · eee304d0-c2ea-44f4-97d9-92a414d31b6c · read 2026-08-30
On people with reduced kidney function, the label states: “Renal function should be evaluated in all patients prior to initiation of ribavirin by estimating the patient’s creatinine clearance.”
US prescribing information · eee304d0-c2ea-44f4-97d9-92a414d31b6c · read 2026-08-30
Where the result stopped carrying
Ribavirin monotherapy does not treat chronic hepatitis C, and the label says so in a boxed warning
Hemolytic anemia has caused fatal and non-fatal myocardial infarction; patients with significant or unstable cardiac disease must not receive it
Teratogenic and embryocidal in every animal species tested, with a contraception requirement extending nine months past the last dose
The original 1985 RSV indication was never confirmed: twelve randomised trials pooled to an odds ratio for mortality of 0.58 with a confidence interval from 0.18 to 1.85
The Lassa fever evidence base, reassessed with unpublished data obtained by Freedom of Information request, was judged incapable of supporting the recommendation it has carried since the 1980s
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 tablet, capsule and solution; separately, an inhalation solution given by small-particle aerosol
✎ 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: S3, S6.
No source is stored against this line.
What is in the pack
The oral forms are used in hepatitis C in combination with peginterferon or with certain direct-acting antiviral regimens. The inhalation solution is a distinct product for hospitalised infants and young children with severe RSV lower respiratory tract infection and is not indicated in adults.
✎ 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
Three boxed warnings on the oral product: embryo-fetal toxicity, hemolytic anemia, and monotherapy not recommended. Contraindicated in pregnancy, in the male partners of pregnant women, and in patients with a history of significant or unstable cardiac disease. The anemia is dose-related and monitored rather than merely watched for. The aerosol product carries separate warnings: accumulated drug precipitate has caused mechanical ventilator dysfunction with raised pulmonary pressures, and sudden deterioration of respiratory function has followed initiation in infants. Occupational exposure of healthcare staff to a teratogenic aerosol is a recognised handling concern.
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 tablet, capsule and solution; separately, an inhalation solution given by small-particle aerosol
✎ 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 inhalation solution is a distinct product for hospitalised infants and young children with severe RSV lower respiratory tract infection and is not indicated in adults.
✎ 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
18 products list this as an active ingredient in the United States drug directory. 18 of them contain it and nothing else.
FDA National Drug Code directory · 37662-4142 · read 2026-08-29
They are sold as capsule, pellet, powder, powder, for solution and tablet, film coated, taken oral and respiratory (inhalation).
FDA National Drug Code directory · 37662-4142 · read 2026-08-29
The regulator's established pharmacologic class for it is nucleoside analog antiviral [epc] and nucleoside analog [ext].
FDA National Drug Code directory · 37662-4142 · read 2026-08-29
5 published labels name it as an active ingredient. 5 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · eee304d0-c2ea-44f4-97d9-92a414d31b6c · read 2026-08-29
Those labels are classed as human otc drug and human prescription drug.
US prescribing information · eee304d0-c2ea-44f4-97d9-92a414d31b6c · read 2026-08-29
Ribavirin is oral at 3 DOSAGE FORMS AND STRENGTHS Ribavirin is available as a light pink colored, capsule shaped, film-coated tablet for oral administration., recorded as fda label in effect 2024-02-06 in the United States.
US prescribing information · eee304d0-c2ea-44f4-97d9-92a414d31b6c · read 2026-08-30
Recorded price in US: 0.45069 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, for the one priced product, 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.
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 Ribavirin 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 the mechanism of action is known — five mechanisms have been proposed, evidence exists for each, and none is established in hepatitis C
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 lethal mutagenesis, demonstrated cleanly in poliovirus, is what ribavirin does in hepatitis C
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 ribavirin reduces mortality in Lassa fever — the association exists in every comparative study and every one of those studies is at critical or serious risk of bias
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 broad in-vitro activity against many RNA viruses predicts clinical benefit against them; the drug is active in a dish against far more viruses than it treats
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 doses in clinical use for Lassa fever reach inhibitory concentrations — modelling suggests they exceed the mean EC90 less than 10% of the time
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 Ribavirin 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.
Adding ribavirin to interferon tripled the hepatitis C cure rate
In plain words
In 1998, 912 people were randomly assigned to interferon alone or interferon with ribavirin. At forty-eight weeks, 13% of those on interferon alone were cured, against 38% of those who also took ribavirin.
What was measured
Sustained virologic response at 24 weeks post-treatment, ribavirin added to interferon against interferon alone
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The Hepatitis Interventional Therapy Group randomised 912 patients with chronic hepatitis C to interferon alfa-2b alone or with ribavirin, for 24 or 48 weeks. Sustained virologic response was 38% (87 of 228) with combination therapy for 48 weeks and 31% (70 of 228) for 24 weeks, against 13% (29 of 225) and 6% (13 of 231) with interferon alone, P<0.001 for both comparisons. Histologic improvement was also more common on combination therapy: 61% and 57% against 41% and 44%. Dose reduction and discontinuation were more frequent with ribavirin.
Written into the record, not signed off as a reviewed claim
A placebo arm isolated ribavirin’s own contribution: 56% against 29%
In plain words
Four years later a larger trial gave everyone the same peginterferon and randomised only whether they also got ribavirin or a matching placebo. Ribavirin nearly doubled the cure rate on its own.
What was measured
Sustained virologic response with ribavirin against matching placebo on identical peginterferon
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Fried and colleagues randomised 1,121 patients to peginterferon alfa-2a with daily ribavirin, peginterferon alfa-2a with daily placebo, or interferon alfa-2b with ribavirin, all for 48 weeks. Sustained virologic response was 56% with peginterferon plus ribavirin against 29% with peginterferon plus placebo (P<0.001) and 44% with interferon alfa-2b plus ribavirin (P<0.001). In genotype 1 the corresponding figures were 46%, 21% and 36%; in genotype 1 with high baseline viral load, 41%, 13% and 33%. The placebo arm is what makes this a measurement of ribavirin rather than of a regimen.
Written into the record, not signed off as a reviewed claim
Forty years in, the mechanism of action is still five hypotheses
In plain words
Nobody has established how ribavirin works. Five separate explanations have been proposed, evidence exists for each of them, and which one applies probably differs between viruses.
What was measured
That ribavirin’s clinical benefit in hepatitis C is explained by any one of its five proposed mechanisms — evidence exists for each and none has been established as the operative one in this disease
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The five proposed mechanisms are two indirect — inhibition of inosine monophosphate dehydrogenase, which depletes the intracellular GTP pool, and immunomodulatory effects — and three direct: interference with viral RNA capping, direct polymerase inhibition, and lethal mutagenesis. The mutagenesis case is the best characterised: ribavirin triphosphate is used by poliovirus 3Dpol and templates cytidine and uridine with equal efficiency, reducing infectious virus production to as little as 0.00001% in cell culture, with antiviral activity correlating directly with mutagenic activity. That is a clean result in poliovirus. It has never been established as the operative mechanism in hepatitis C, where ribavirin alone barely moves viral load at all.
Written into the record, not signed off as a reviewed claim
The label carries a boxed warning that the drug does not work alone
In plain words
One of the three boxed warnings on ribavirin says, in plain terms, that ribavirin by itself does not treat chronic hepatitis C and must not be used that way.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The boxed warning is headed EMBRYO-FETAL TOXICITY, HEMOLYTIC ANEMIA, and MONOTHERAPY NOT RECOMMENDED, and states that ribavirin monotherapy is not effective for the treatment of chronic hepatitis C virus infection and should not be used alone for this indication. This is a rare thing for a label to say about its own product, and it is the single clearest statement of the gap between ribavirin’s broad in-vitro activity and its narrow clinical effect: against hepatitis C the measurable benefit appears only in combination, largely as a reduction in relapse after treatment stops rather than as faster viral clearance during it.
Source
Ribavirin tablets United States prescribing information, boxed warning (Aurobindo Pharma Limited labelling, openFDA)
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
Hemolytic anemia that has led to fatal myocardial infarction
In plain words
Ribavirin destroys red blood cells. In people whose hearts were already struggling, the resulting anemia has caused heart attacks, some of them fatal. It is also teratogenic in every animal species that has been tested, and it stays in the body for months.
What was measured
Multiple-dose half-life of 12 days; persistence in tissue up to 6 months
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The boxed warning records that hemolytic anemia has been reported with ribavirin therapy and may result in worsening of cardiac disease that has led to fatal and non-fatal myocardial infarctions; patients with a history of significant or unstable cardiac disease should not be treated. Separately, significant teratogenic and embryocidal effects have been demonstrated in all animal species exposed to ribavirin; the multiple-dose half-life is 12 days and the drug may persist in non-plasma compartments for as long as six months, which is why the contraception requirement extends nine months beyond treatment in female patients and six months in the female partners of male patients. The mechanism of the anemia is straightforward and follows from the drug’s chemistry: erythrocytes phosphorylate ribavirin and lack the phosphatase to reverse it, so the triphosphate accumulates and the cell is destroyed.
Source
Ribavirin tablets United States prescribing information, boxed warning and Warnings and Precautions 5.1 and 5.2 (openFDA)
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
Lassa fever: the only treatment there is, and the evidence for it has collapsed
In plain words
Ribavirin has been the standard treatment for Lassa fever in West Africa since the 1980s, on the strength of a single study. Reanalysis of that study and of every other comparison found all of them critically biased, and one reanalysis raised the possibility that ribavirin is harmful in some patients.
What was measured
Risk-of-bias assessment of all 13 comparative studies: critical or serious on ROBINS-I
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
A systematic review searching published and unpublished literature to March 2022, including data obtained from a Sierra Leone study through a United States Freedom of Information Act request, identified 13 studies comparing ribavirin against no ribavirin on mortality. Ribavirin was associated with decreased mortality in these studies, but every one was at critical or serious risk of bias on the ROBINS-I tool, with problems of uncontrolled confounding, immortal time bias and missing outcome data. The authors concluded that robust evidence supporting the use of ribavirin in Lassa fever is lacking. A companion systematic review of pre-clinical and pharmacokinetic data found in-vitro EC50 values spanning 0.6 to 21.72 micrograms per millilitre and modelling suggesting current regimens exceed the mean EC50 for less than 20% of the time and the mean EC90 for less than 10% — meaning the doses in clinical use may not reach the concentrations that inhibit the virus. The same authors, writing separately, stated that reanalysis of previously unpublished data reveals ribavirin may actually be harmful in some Lassa fever patients.
Written into the record, not signed off as a reviewed claim
The 1985 approval, for RSV, was never confirmed by an adequately powered trial
In plain words
Ribavirin’s original approval was as a mist for infants with severe RSV. Twenty-five years and twelve randomised trials later, the pooled mortality difference was still not statistically significant, and the reviewers said the trials were too small to answer the question.
What was measured
Pooled mortality odds ratio 0.58 (95% CI 0.18 to 1.85) across four randomised trials, 158 participants
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The Cochrane review of aerosolised ribavirin for RSV lower respiratory tract infection included 12 randomised trials, all in infants under six months. Across four trials with 158 participants, mortality was 5.8% with ribavirin against 9.7% with placebo, odds ratio 0.58 (95% CI 0.18 to 1.85). Across three trials with 116 participants, respiratory deterioration was 7.1% against 18.3%, odds ratio 0.37 (95% CI 0.12 to 1.18). In three studies of 104 ventilated participants the mean difference was 1.9 fewer days of hospitalisation (95% CI -4.6 to +0.9) and 1.8 fewer days of ventilation (95% CI -3.4 to -0.2). The reviewers concluded that trials of ribavirin for RSV lack sufficient power to provide reliable estimates of the effects. The aerosol label carries its own separate warnings about drug precipitate causing mechanical ventilator dysfunction and about sudden deterioration of respiratory function in infants.
Written into the record, not signed off as a reviewed claim
From the backbone of every hepatitis C regimen to almost nothing
In plain words
Between 1998 and 2013 no hepatitis C regimen omitted ribavirin. Within about five years of the direct-acting antivirals arriving, it had been designed out of nearly every recommended course.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The change was not driven by a trial that tested ribavirin and found it wanting. It was driven by regimens that reached cure rates in the high nineties without it: where an eight or twelve week all-oral course cures more than 95%, the 27-point contribution ribavirin made on top of peginterferon has no room left to act, and its hemolytic anemia becomes pure cost. Ribavirin survives in a small number of specific situations named in direct-acting antiviral labels, and as the only agent for Lassa fever. The trajectory is the ordinary one for an adjunct whose value was always relative to a weak backbone, but it is worth recording that a drug can go from indispensable to near-obsolete without any new evidence about the drug itself.
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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 guanosine mimic with five separate proposed mechanisms and none established, which tripled interferon’s hepatitis C cure rate in a 912-patient randomised trial (38% against 13% at 48 weeks) and added 27 points on top of peginterferon in a 1,121-patient trial (56% against 29%), while carrying a boxed warning that it does not work alone, that its hemolytic anemia has caused fatal myocardial infarction, and that it is teratogenic in every animal species tested.
Recorded evidence blocks (10)
Q2
On the Ribavirin label: indicated for what?
"Ribavirin for Inhalation Solution, USP is indicated for the treatment of hospitalized infants and young children with severe lower respiratory tract infections due to RSV. Treatment early in the course of severe lower respiratory tract infection may be necessary to achieve efficacy.": indications and usage on Ribavirin's label. DailyMed label · 3631ee95-692a-4426-8edf-62c27f7c32cb · 2024-02-09
Q3
601 registered trials of Ribavirin — at which phases?
Registered studies posting no result
279 of 601
601 registered studies of Ribavirin: 234 phase2, 182 phase3, 93 phase4, 67 na or unstated, 36 phase1, 20 na, 2 early phase1. CLINICALTRIALS_SNAPSHOT · 2026-09-01
"The PI left the institution."; 60 of 601 registered studies
Show the evidence
Trial
NCT00167557
withdrawn; "The PI left the institution."
NCT00255008
terminated; "Slow enrollment"
NCT00255034
terminated; "Recruitment targets were unachievable in the currently available population."
NCT00277758
terminated; "Insufficient rate of volunteer accrual."
NCT00441584
terminated; "Subject accrual was prematurely terminated due slow enrollment."
NCT00571714
withdrawn; "lack of enrollment"
14 further recorded trials
NCT00623168
withdrawn; "This was an expanded access treatment protocol that did not enroll any subjects due to no infections requiring treatment."
NCT00641654
terminated; "Recruitment problems in Denmark and Norway"
NCT00662220
terminated; "Due to the arrival of DAAs replacing standard of care for genotype 1 patients the VIRID study had to be terminated."
NCT00689390
terminated; "The study was terminated due to satisfaction of post-marketing commitments"
NCT00723879
terminated; "Because of slow recruitment; Despite the study was started long time ago (Oct 2004), we have not reached the projected number of patients (150 patients)"
NCT00725842
terminated; "Low enrollment"
NCT00727077
terminated; "Study halted due to low recruitment. The 3 participants at time of termination transferred into study P04538 (NCT00727077). See NCT00727077 for details/results."
NCT00803309
terminated; "At the end of the planned recruitment period the expected number of subjects could not be included in the trial."
NCT00814606
withdrawn; "no one ever enrolled"
NCT00840489
terminated; "Preliminary analysis"
NCT00868946
withdrawn; "Lack of enrollment"
NCT00882193
terminated; "new medications with improved response released"
NCT00897312
terminated; "slow accrual"
NCT01056757
terminated; "Study closed because of new overlapping study with ribavirin."
recorded 2026-09-01 · last checked 2026-09-04
Q5
Human studies of Ribavirin used Ribavirin 200 mg tablets — over how long?
studies of Ribavirin used the recorded amount. ClinicalTrials.gov · 2026-09-01
9.5 hours; The plasma half-life was reported to be 9.5 hours.
recorded 2024-02-09 · last checked 2026-09-04
Q7
Which 185 trials of Ribavirin posted no result?
Posted no result
185 of 185 completed trials
Registrations
NCT00001015, NCT00000733, NCT00000772, NCT00000833, NCT00960479 and NCT00014391, and 179 more
Completion dates
oldest 1990-06; newest 2022-12-30
Show the evidence
Trial
NCT00001015
1990-06
NCT00000733
1991-10
NCT00000772
1995-02
NCT00000833
1998-07
NCT00960479
2001-02
NCT00014391
2001-10
14 further recorded trials
NCT00001729
2002-09
NCT00016081
2003-03
NCT00221624
2004-04
NCT00221650
2004-06
NCT00158496
2005-01
NCT00015652
2005-03
NCT00055341
2005-06
NCT00059358
2005-06
NCT00248339
2005-07
NCT00001123
2005-11
NCT00038974
2005-11
NCT00363259
2005-11
NCT00211848
2005-12
NCT00230958
2006-01
Q8
At the median, Ribavirin's trials enrolled 104 people — anything larger?
Median enrolment
104
Largest enrolment
10228
Registered trials counted
595
Q9
What do 25954 spontaneous reports say about Ribavirin — 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.
Ribavirin appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 25954 reaction mentions were counted: anaemia 5817; fatigue 3380; nausea 2889; rash 2605. FAERS via Open Targets · CHEMBL1643 · 2026-06-24
Show the evidence
anaemia
5817
fatigue
3380
nausea
2889
rash
2605
white blood cell count decreased
2007
haemoglobin decreased
2002
4 more recorded rows
hepatitis c
2000
pyrexia
1826
platelet count decreased
1716
asthenia
1712
recorded 2026-06-24 · last checked 2026-09-04
Q10
Which 10 reactions does Ribavirin's label not list?
ChEMBL 37 — CC BY-SA 3.0 Unported · ChEMBL ATC CC BY-SA · ClinicalTrials.gov — US Government work · EMA medicine register · 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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✓ public claims reviewed: 0 reviewed claim(s); drafts are never rendered
✓ source coverage passed: 8 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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