This page shows what was measured, who it was measured in, and what that does not settle.
What Valaciclovir does in the body
Used for shingles, cold sores and genital herpes.
Valacyclovir is a delivery trick. Acyclovir itself is poorly absorbed from the gut, so an amino acid is bolted on, which lets a nutrient transporter carry it across the intestinal wall. Once inside, the body cuts the amino acid off. The freed drug is then activated only inside infected cells, because only a herpes virus makes the enzyme that switches it on. The activated form is then fed to the viral copying machine, which incorporates it and stalls permanently.
What happened in people
Daily treatment cut symptomatic genital-herpes transmission to an uninfected partner by three quarters over eight months.
✓ 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
Lower virus shedding did not translate into benefit for several other diseases where it was tested.
Where it acts
Herpesvirus-infected epithelial and neuronal cells; the drug is activated only where viral thymidine kinase is present
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
Its recorded molecular formula is C13H20N6O4•HCl, weighing 360.80.
US prescribing information · 3277c17e-f953-2b0a-fe0a-4f5d1aeace9d · read 2026-08-30
Where each sentence above came from
No recorded sentence describes the change this makes in a way that stands on its own. The page opens with what it is taken for instead, and the recorded explanation follows below.
Shown as the opening line on this page.
The limit a reviewer approved as the one that matters most here.
The four opening statements run to 105 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.
Reduction in transmission of symptomatic genital herpes to the initially susceptible partner over 8 months
✓ The study showed what it set out to show
Who was studied
Corey HSV-2 transmission trial
How many people
1484
Study design
Randomised double-blind placebo-controlled
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
P = 0.008 (hazard ratio 0.25, 95% CI 0.08 to 0.75)
Repeated elsewhere
Unreplicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Overall acquisition including asymptomatic seroconversion fell less steeply, hazard ratio 0.52 (P=0.04), so the headline figure is specific to symptomatic infection.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet and oral suspension
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
Genetically linked HIV-1 transmission within serodiscordant couples
✗ The study did not show it
Who was studied
Partners in Prevention HSV/HIV Transmission Study (NCT00194519)
How many people
3408
Study design
Phase 3 randomised placebo-controlled
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
P = 0.69 (hazard ratio 0.92, 95% CI 0.60 to 1.41)
Repeated elsewhere
Replicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. The intervention worked on every intermediate measure: genital ulcers fell 73% and plasma HIV-1 RNA fell 0.25 log10, with no effect on the endpoint.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet and oral suspension
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
RNAWiki holds 5 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
Valaciclovir
What a person takes: Oral tablet and oral suspension.
The measurement behind this step
Once or twice daily for suppression, higher and more frequent for shingles or an acute episode. The whole design of the molecule is oral delivery: the L-valyl ester is a substrate for the intestinal peptide transporter PEPT1, which raises acyclovir bioavailability from roughly 10 to 20% to about 55% and converts a five-times-daily drug into a once-daily one.
Getting in
An amino acid tag gets it through the gut wall
Acyclovir on its own is barely absorbed. Attaching valine to it lets a nutrient transporter carry it across the intestinal lining.
╌╌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 L-valyl ester is a substrate for the intestinal peptide transporter PEPT1. Oral bioavailability of acyclovir rises from roughly 10 to 20% for acyclovir itself to about 55% for valacyclovir, which is what makes once or twice daily suppression practical. The stereochemistry matters: the D-valyl ester is not a PEPT1 substrate.
Enzymes in the gut wall and liver snip the valine off, freeing the real drug.
╌╌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
Valacyclovir hydrolase in intestinal and hepatic tissue cleaves the ester almost completely on first pass, so systemic exposure is to acyclovir. Valacyclovir itself has no meaningful antiviral activity; every pharmacological statement below is about acyclovir.
The drug is activated by an enzyme that only the herpes virus makes, so uninfected cells leave it alone.
──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
Herpesvirus thymidine kinase, encoded by UL23, adds the first phosphate. Host kinases add the second and third. Uninfected cells phosphorylate acyclovir hundreds of times less efficiently, which is the source of the selectivity. Thymidine-kinase-deficient viral mutants are resistant and are the commonest resistance mechanism in immunocompromised patients.
The virus copying machine picks up the activated drug, adds it to the growing DNA strand, and cannot continue because the drug has no attachment point for the next unit.
╌╌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
Acyclovir triphosphate competes with deoxyguanosine triphosphate for the viral DNA polymerase encoded by UL30 and is incorporated into the elongating strand. Lacking a 3-hydroxyl, it is an obligate chain terminator, and the terminated primer-template then inactivates the polymerase in a suicide fashion.
Shedding and recurrences fall, and the latent virus remains
Outbreaks become rarer and shorter and shedding drops sharply, but the virus stays in the nerve cells for life.
╌╌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 drug acts only on replicating virus, so latent genomes in sensory ganglia are untouched. In the Corey trial suppression cut HSV DNA detection from 10.8% to 2.9% of days and recurrences from 0.40 to 0.11 per month, and stopping the drug returns both to baseline.
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 with recurrent genital herpes taking suppressive therapy, people with shingles or cold sores taking episodic treatment, and members of serodiscordant couples where reducing transmission is the goal.
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 efficacy and safety of valacyclovir have not been established in pediatric patients: aged less than 12 years with cold sores aged less than 18 years with genital herpes aged less than 18 years with herpes zoster aged less than 2 years with chickenpox for suppressive therapy following neonatal HSV infection.”
US prescribing information · 3277c17e-f953-2b0a-fe0a-4f5d1aeace9d · read 2026-08-30
On older people, the label states: “Of the total number of subjects in clinical trials of valacyclovir hydrochloride, 906 were 65 and over, and 352 were 75 and over.”
US prescribing information · 3277c17e-f953-2b0a-fe0a-4f5d1aeace9d · read 2026-08-30
On people who are pregnant, the label states: “Risk Summary Clinical data over several decades with valacyclovir and its metabolite, acyclovir, in pregnant women, have not identified a drug associated risk of major birth defects.”
US prescribing information · 3277c17e-f953-2b0a-fe0a-4f5d1aeace9d · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary Although there is no information on the presence of valacyclovir in human milk, its metabolite, acyclovir, is present in human milk following oral administration of valacyclovir.”
US prescribing information · 3277c17e-f953-2b0a-fe0a-4f5d1aeace9d · read 2026-08-30
On people with reduced kidney function, the label states: “Dosage reduction is recommended when administering valacyclovir hydrochloride to patients with renal impairment [see Dosage and Administration ( 2.4 ), Warnings and Precautions ( 5.2 , 5.3 )].”
US prescribing information · 3277c17e-f953-2b0a-fe0a-4f5d1aeace9d · read 2026-08-30
Where the result stopped carrying
Partners in Prevention: no reduction in genetically linked HIV-1 transmission despite every intermediate measure moving in the expected direction
VALAD: the primary cognitive endpoint moved against the drug
Bell palsy: no benefit from acyclovir alone or added to prednisolone
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 and oral suspension
✎ 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
Once or twice daily for suppression, higher and more frequent for shingles or an acute episode.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold. The rest of the recorded wording: The whole design of the molecule is oral delivery: the L-valyl ester is a substrate for the intestinal peptide transporter PEPT1, which raises acyclovir bioavailability from roughly 10 to 20% to about 55% and converts a five-times-daily drug into a once-daily one.
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
Generally well tolerated, with headache and nausea the commonest complaints. Acyclovir is renally cleared and can crystallise in renal tubules, so dose reduction is required in renal impairment and adequate hydration matters at high doses; the VALAD trial at 4 g per day found elevated creatinine in 8.3% of participants. Thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome have been reported at high doses in advanced HIV and in transplant recipients. Neurotoxicity occurs mainly in renal impairment.
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 and oral suspension
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
A recorded note compares this form with the others that are sold. It is kept below, word for word.
§ A fixed RNAWiki sentence
Where this came from
Wording RNAWiki always uses, not a finding about this substance.
The recorded note, unchanged: The whole design of the molecule is oral delivery: the L-valyl ester is a substrate for the intestinal peptide transporter PEPT1, which raises acyclovir bioavailability from roughly 10 to 20% to about 55% and converts a five-times-daily drug into a once-daily one.
No source is stored against this line.
What is recorded as being sold
126 products list this as an active ingredient in the United States drug directory. 126 of them contain it and nothing else.
FDA National Drug Code directory · 82009-040 · read 2026-08-29
They are sold as powder, tablet and tablet, film coated, taken oral.
FDA National Drug Code directory · 82009-040 · read 2026-08-29
The regulator's established pharmacologic class for it is dna polymerase inhibitors [moa], herpes simplex virus nucleoside analog dna polymerase inhibitor [epc] and herpes zoster virus nucleoside analog dna polymerase inhibitor [epc].
FDA National Drug Code directory · 82009-040 · read 2026-08-29
93 published labels name it as an active ingredient. 93 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · 3277c17e-f953-2b0a-fe0a-4f5d1aeace9d · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · 3277c17e-f953-2b0a-fe0a-4f5d1aeace9d · read 2026-08-29
Valacyclovir Hydrochloride is film-coated tablets at 500 mg or 1 gram of valacyclovir (containing 556.2 mg or 1.112 grams of valacyclovir hydrochloride), recorded as prescription product; fda label in effect 2026-05-28 in the United States.
US prescribing information · 021ab9d0-7b75-40cf-afde-446942d64388 · read 2026-08-27
Recorded price in US: 0.22403–0.40461 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 48 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 Valaciclovir 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 suppressing HSV-2 reduces HIV-1 transmission or acquisition — tested from both directions and refuted in both
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 an epidemiological association between herpes simplex virus and Alzheimer disease implies a treatable causal role
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 reduced viral shedding is a general surrogate for clinical benefit rather than one specific to the herpes transmission endpoint
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 Valaciclovir 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.
Symptomatic HSV-2 transmission fell from 16 of 741 partners to 4 of 743
In plain words
In 1,484 couples where one partner had genital herpes and the other did not, daily valacyclovir cut symptomatic transmission by three quarters over eight months.
What was measured
Clinically symptomatic HSV-2 acquisition in the initially susceptible partner over 8 months
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Randomised, placebo-controlled trial in immunocompetent, heterosexual, monogamous couples. The source partner took valacyclovir 500 mg once daily or placebo for eight months; both partners were counselled on safer sex and offered condoms at every visit. Clinically symptomatic HSV-2 infection developed in 4 of 743 partners on valacyclovir versus 16 of 741 on placebo, hazard ratio 0.25 (95% CI 0.08 to 0.75; P=0.008). Overall acquisition, including asymptomatic seroconversion, was 14 of 743 (1.9%) versus 27 of 741 (3.6%), hazard ratio 0.52 (95% CI 0.27 to 0.99; P=0.04). HSV DNA was detected on 2.9% of days versus 10.8% (P<0.001), and recurrences averaged 0.11 versus 0.40 per month (P<0.001).
Written into the record, not signed off as a reviewed claim
Partners in Prevention: suppressing HSV-2 reduced ulcers and viral load and did not reduce HIV-1 transmission
In plain words
The drug did exactly what it was supposed to do biologically and did not change the outcome anyone cared about.
What was measured
Genetically linked HIV-1 transmission within serodiscordant couples
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
Randomised, placebo-controlled trial of acyclovir 400 mg twice daily in 3,408 African couples where the HIV-1-positive partner was also HSV-2-positive and not on antiretroviral therapy. Of 132 seroconversions, 84 were genetically linked within couples: 41 in the acyclovir group and 43 on placebo, hazard ratio 0.92 (95% CI 0.60 to 1.41; P=0.69). In the same trial acyclovir reduced plasma HIV-1 RNA by 0.25 log10 copies per millilitre (P<0.001) and HSV-2-positive genital ulcers by 73% (risk ratio 0.27; P<0.001). Adherence was 96%.
Written into the record, not signed off as a reviewed claim
The mirror-image trial in HIV-negative people also found nothing
In plain words
Giving the drug to uninfected people with genital herpes did not protect them from acquiring HIV either.
What was measured
That HSV-2 suppression is a viable HIV prevention strategy because HSV-2 ulceration facilitates HIV transmission
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
A phase 3 double-blind, randomised, placebo-controlled trial of acyclovir 400 mg twice daily for 12 to 18 months in HSV-2-seropositive, HIV-1-seronegative women in Africa and men who have sex with men in Peru and the United States. 3,172 participants were in the primary dataset. HIV-1 incidence was 3.9 per 100 person-years on acyclovir (75 events) and 3.3 on placebo (64 events), hazard ratio 1.16 (95% CI 0.83 to 1.62). Genital ulcers on examination fell 47% and HSV-2-positive ulcers 63%. Together with Partners in Prevention this closes the hypothesis from both directions: neither suppressing the virus in the person transmitting HIV nor in the person at risk of acquiring it changed HIV incidence.
Written into the record, not signed off as a reviewed claim
VALAD: valacyclovir for Alzheimer disease worsened the cognitive endpoint
In plain words
A hypothesis that herpes virus drives Alzheimer disease was tested with 78 weeks of high-dose valacyclovir. The treated group declined more than the placebo group.
What was measured
Least-squares mean change in ADAS-Cognitive subscale score at 78 weeks
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
Randomised, double-blind, placebo-controlled trial at three US memory clinics. 120 participants with probable Alzheimer disease or biomarker-positive mild cognitive impairment, all HSV-1 or HSV-2 seropositive, received valacyclovir 4 g per day (n=60) or placebo (n=60) for 78 weeks; 93 (77.5%) completed. Least-squares mean change in the 11-item ADAS-Cognitive subscale was 10.86 (95% CI 8.80 to 12.91) with valacyclovir and 6.92 (95% CI 4.88 to 8.97) with placebo, a between-group difference of 3.93 (95% CI 1.03 to 6.83; P=0.01) in the direction of greater worsening on drug. Amyloid and tau PET showed no between-group difference. Elevated serum creatinine occurred in 8.3% versus 3.3%.
Written into the record, not signed off as a reviewed claim
Bell palsy: the steroid worked and the antiviral did not
In plain words
A factorial trial gave patients prednisolone, acyclovir, both or neither. Only the steroid made a difference.
What was measured
Recovery of facial function on the House-Brackmann scale
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
Double-blind, placebo-controlled, randomised factorial trial in 551 patients recruited within 72 hours of onset, with final outcomes for 496. Recovery of facial function at 3 months was 83.0% with prednisolone versus 63.6% without (P<0.001), and 71.2% with acyclovir versus 75.7% without (adjusted P=0.50). At 9 months, 94.4% versus 81.6% for prednisolone (P<0.001) and 85.4% versus 90.8% for acyclovir (adjusted P=0.10). There was no additional benefit of acyclovir added to prednisolone.
Written into the record, not signed off as a reviewed claim
Reducing shedding is a surrogate, and it predicted one outcome out of four
In plain words
Valacyclovir reliably reduces how much virus is shed. That surrogate predicted the herpes transmission result and failed to predict three others.
What was measured
That suppression of viral shedding is a general surrogate for clinical benefit wherever the virus is implicated
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
In the Corey trial, HSV DNA detection fell from 10.8% to 2.9% of days and symptomatic transmission fell in proportion. In Partners in Prevention, genital ulcers fell 73% and plasma HIV-1 RNA fell 0.25 log10 and linked HIV transmission did not move at all. In VALAD, 78 weeks of suppression at eight times the usual suppressive dose produced worse cognitive scores. A surrogate that tracks the clinical endpoint in one disease is not thereby a surrogate in another, and this drug provides an unusually clean four-trial demonstration of that.
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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 valine ester prodrug of acyclovir that raised oral bioavailability enough to make suppression practical, and cut symptomatic HSV-2 transmission from 16 of 741 to 4 of 743 partners over eight months, while failing to reduce HIV-1 transmission, HIV-1 acquisition, Bell palsy recovery or Alzheimer disease progression in four separate randomised trials.
Recorded evidence blocks (9)
Q1
On the Valaciclovir label: indicated for what?
"Valacyclovir tablets are a deoxynucleoside analogue DNA polymerase inhibitor indicated for: Adult Patients ( 1.1 ) Cold Sores (Herpes Labialis) Genital Herpes Treatment in immunocompetent patients (initial or recurrent episode) Suppression in immunocompetent or HIV-1-infected patients Reduction of transmission Herpes…": indications and usage on Valaciclovir's label. DailyMed label · 59e104dd-6356-e323-e063-6394a90a6396 · 2026-08-25
Q2
113 registered trials of Valaciclovir — at which phases?
Registered studies posting no result
84 of 113
113 registered studies of Valaciclovir: 37 phase2, 28 phase1, 17 na, 16 phase4, 15 phase3, 3 na or unstated. CLINICALTRIALS_SNAPSHOT · 2026-09-01
187 with a PubMed record
Show the evidence
phase2
37
phase1
28
na
17
phase4
16
phase3
15
na or unstated
3
8 more recorded rows
completed
80
recruiting
9
terminated
8
unknown
7
active not recruiting
3
withdrawn
3
not yet recruiting
2
enrolling by invitation
1
recorded 2026-09-01 · last checked 2026-09-04
Q3
8 of Valaciclovir's trials stopped: safety, futility/efficacy, accrual/recruitment, funding/business, other?
safety (2), futility/efficacy (1), accrual/recruitment (1), funding/business (1) and other (3): Valaciclovir's stop wording, clustered. CLINICALTRIALS_SNAPSHOT · 2026-09-01
"Terminated"; 8 of 113 registered studies
Show the evidence
Trial
NCT00079911
terminated; "Terminated"
NCT00682721
withdrawn; "Sponsor has withdrawn support for this study and it will not be performed"
NCT00870441
terminated; "Study terminated due to treatment-emergent serious adverse events"
NCT01037712
terminated; "not enough inclusion"
NCT01059084
withdrawn; "We were unable to enroll any participants into this study."
NCT02831933
terminated; "Lack of funding"
2 further recorded trials
NCT03699904
terminated; "In light of the evolving Covid19 pandemic ongoing study recruitment was felt to pose an unacceptable risk to patient safety."
NCT04081480
terminated; "Interim analysis showed positive results, it was difficult to include patients and also the fact that the grant for this project has ended, we have decided to complete the study before we had included the total number of 16 patients."
recorded 2026-09-01 · last checked 2026-09-04
Q4
Human studies of Valaciclovir used Valacyclovir Hydrochloride Tablets 1000 mg — over how long?
Human studies of Valaciclovir used "Valacyclovir Hydrochloride Tablets 1000 mg". ClinicalTrials.gov · 2026-09-01
9 recorded entries; human; also "Valtrex® Tablets 1000 mg", "Valacyclovir Hydrochloride Tablets 1000mg", "Valtrex® 1000 mg"
Show the evidence
human
NCT00649870
Valacyclovir Hydrochloride Tablets 1000 mg
NCT00649870
Valtrex® Tablets 1000 mg
NCT00650494
Valacyclovir Hydrochloride Tablets 1000mg
NCT00650494
Valtrex® 1000 mg
NCT02997982
Valaciclovir 500Mg Tablet
NCT05266040
Valacyclovir 500 MG
3 more recorded rows
humanNCT05550194
ValACYclovir 1000 MG
humanNCT06344195
Valacyclovir 500 mg
humanNCT06344195
Valtrex 500mg
recorded 2026-09-01 · last checked 2026-09-04
Q5
Which running trial of Valaciclovir could settle lifespan?
NCT02768363 measures Progression-free survival (PFS), reading out 2026-12.
2 open trials; n 187; "Randomized Controlled Trial of CAN-2409 Immunotherapy During Active Surveillance for Prostate Cancer (ULYSSES)"
Show the evidence
Trial
NCT02768363
"Randomized Controlled Trial of CAN-2409 Immunotherapy During Active Surveillance for Prostate Cancer (ULYSSES)"; n 187; "Progression-free survival (PFS)"; 2026-12
NCT07660094
"Aglatimagene Besadenovec + Prodrug and Pembrolizumab vs Docetaxel for Stage IV Non-Squamous NSCLC Progressing on Pembrolizumab (AURORA)"; n 500; "Overall Survival"; 2031-10-22
Q6
Which 47 trials of Valaciclovir posted no result?
Posted no result
47 of 47 completed trials
Registrations
NCT00001649, NCT00378976, NCT00045292, NCT01149499, NCT00042328 and NCT00649974, and 41 more
Completion dates
oldest 2003-08; newest 2023-07-22
Show the evidence
Trial
NCT00001649
2003-08
NCT00378976
2004-07
NCT00045292
2004-10
NCT01149499
2005-01
NCT00042328
2005-05
NCT00649974
2005-05
14 further recorded trials
NCT00059592
2005-05-05
NCT00649870
2005-06
NCT00158509
2005-07
NCT00343278
2005-08
NCT00650494
2005-08
NCT00274404
2005-09
NCT00161434
2006-06
NCT00562770
2006-07
NCT01132716
2006-09
NCT01132729
2006-09
NCT00297206
2007-02-28
NCT01136525
2007-05
NCT01136538
2007-05
NCT01250561
2007-10
Q7
At the median, Valaciclovir's trials enrolled 50 people — anything larger?
Median enrolment
50
Largest enrolment
1200
Registered trials counted
109
Q8
What do 2920 spontaneous reports say about Valaciclovir — 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.
Valaciclovir appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 2920 reaction mentions were counted: renal failure acute 414; altered state of consciousness 322; pyrexia 322; dysarthria 296. FAERS via Open Targets · CHEMBL1201110 · 2026-06-24
Show the evidence
renal failure acute
414
altered state of consciousness
322
pyrexia
322
dysarthria
296
dizziness
288
blood creatinine increased
284
4 more recorded rows
confusional state
262
encephalopathy
250
depressed level of consciousness
249
acute kidney injury
233
recorded 2026-06-24 · last checked 2026-09-04
Q9
Which 10 reactions does Valaciclovir's label not list?
ChEMBL 37 — CC BY-SA 3.0 Unported · 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
✗ required summary fields resolved: 4 required field(s) not terminal: Why people use it, Best-supported result, Biggest unanswered question, Human evidence
✓ public claims reviewed: 0 reviewed claim(s); drafts are never rendered
✓ source coverage passed: 6 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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