Valacyclovir
Prescription ·Exploratory record · not publication-reviewed ·Updated July 13, 2026
The L-valyl ester prodrug of acyclovir, providing 3-5 times higher oral bioavailability than acyclovir. This allows less frequent dosing (2-3 times daily vs 5 times daily) with equivalent or superior efficacy. Used for genital herpes (initial, recurrent, and suppressive therapy), herpes zoster (shingles), herpes labialis (cold sores), and reduction of HSV transmission to uninfected partners. The preferred oral agent for herpes infections in most clinical scenarios.
Exploratory record, not a reviewed medical publication.
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This generated database record has not completed a claim-level review by a qualified human medical reviewer. Bibliography links and evidence labels are not approval. The page remains available for reference and is excluded from search indexing.
What the research says.
A quick, data-only summary. The full evidence, dosing, and sources are below.
The L-valyl ester prodrug of acyclovir, providing 3-5 times higher oral bioavailability than acyclovir. NutriStack rates the supporting evidence as strong. Common adult dosing is Genital herpes initial: 1 g BID x 10 days; recurrent: 500 mg BID x 3 days; suppressive: 500 mg-1 g daily; herpes zoster: 1 g TID x 7 days; cold sores: 2 g BID x 1 day (as prescribed by your physician), though a prescriber sets the actual dose. This profile indexes 10 sources.
- Treats and suppresses genital herpes (preferred oral agent)6,3
- Treats herpes zoster (shingles), better bioavailability than acyclovir3,4
- Treats herpes labialis (cold sores), 1-day treatment3,6
- Reduces transmission of genital HSV-2 to uninfected partners by ~50%6
- Convenient dosing (2-3 times daily vs 5 times daily for acyclovir)8,10
The bottom line
Evidence rating strong. Most-documented uses: treats and suppresses genital herpes (preferred oral agent), treats herpes zoster (shingles), better bioavailability than acyclovir, treats herpes labialis (cold sores), 1-day treatment. 10 sources indexed (2023–2026), with 0 interaction records on file.
How it works, mechanistically.
Core mechanism
Rapidly converted to acyclovir and L-valine by first-pass intestinal and hepatic esterases (valacyclovir hydrolase). Acyclovir is then selectively phosphorylated by viral thymidine kinase in HSV/VZV-infected cells and subsequently by cellular kinases to acyclovir triphosphate. The active triphosphate competitively inhibits viral DNA polymerase and serves as a DNA chain terminator upon incorporation into viral DNA, halting replication.1,8
Dosing & protocol.
Oral bioavailability of acyclovir from valacyclovir is approximately 54% (vs 15-30% for oral acyclovir). Food does not significantly affect absorption. Rapidly and nearly completely converted to acyclovir after absorption. Maintain adequate hydration.3,4
Full safety detail.
Side effects
- Headache
- Nausea
- Abdominal pain
- Dizziness
- Renal impairment (rare, especially with high doses in immunocompromised)
- Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS, rare, in immunocompromised at high doses)
Sources, by evidence tier.
Numbered references. Citations throughout the page link here.
Meta-analyses & systematic reviews
1- 1The effect of valacyclovir on secondary prevention of congenital cytomegalovirus infection, following primary maternal infection acquired periconceptionally or in the first trimester of pregnancy. An individual patient data meta-analysisPMIDChatzakis C, Shahar-Nissan K, Faure-Bardon V et al. · American journal of obstetrics and gynecology · 2024
Chatzakis C, Shahar-Nissan K, Faure-Bardon V et al.. The effect of valacyclovir on secondary prevention of congenital cytomegalovirus infection, following primary maternal infection acquired periconceptionally or in the first trimester of pregnancy. An individual patient data meta-analysis. American journal of obstetrics and gynecology. 2024
Randomized controlled trials
4- 2Valacyclovir Treatment of Early Symptomatic Alzheimer Disease: The VALAD Randomized Clinical TrialPMIDDevanand DP, Wisniewski T, Razlighi Q et al. · JAMA · 2026
Devanand DP, Wisniewski T, Razlighi Q et al.. Valacyclovir Treatment of Early Symptomatic Alzheimer Disease: The VALAD Randomized Clinical Trial. JAMA. 2026
- 3Low-Dose Valacyclovir in Herpes Zoster Ophthalmicus: The Zoster Eye Disease Randomized Clinical TrialPMIDCohen EJ, Troxel AB, Liu M et al. · JAMA ophthalmology · 2025
Cohen EJ, Troxel AB, Liu M et al.. Low-Dose Valacyclovir in Herpes Zoster Ophthalmicus: The Zoster Eye Disease Randomized Clinical Trial. JAMA ophthalmology. 2025
- 4Low-Dose Valacyclovir for Postherpetic Neuralgia in the Zoster Eye Disease Study: A Randomized Clinical TrialPMIDWarner DB, Jeng BH, Kim J et al. · JAMA ophthalmology · 2025
Warner DB, Jeng BH, Kim J et al.. Low-Dose Valacyclovir for Postherpetic Neuralgia in the Zoster Eye Disease Study: A Randomized Clinical Trial. JAMA ophthalmology. 2025
- 5Valaciclovir for Epstein-Barr Virus Suppression in Moderate-to-Severe COPD: A Randomized Double-Blind Placebo-Controlled TrialPMIDLinden DA, Guo-Parke H, McKelvey MC et al. · Chest · 2023
Linden DA, Guo-Parke H, McKelvey MC et al.. Valaciclovir for Epstein-Barr Virus Suppression in Moderate-to-Severe COPD: A Randomized Double-Blind Placebo-Controlled Trial. Chest. 2023
Reference material
5- 6Corey L et al. Once-daily valacyclovir to reduce the risk of transmission of genital herpes. N Engl J Med. 2004.Source linkedPMID
- 7Workowski KA et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021.Source linkedPMID
- 8Tyring SK et al. Valaciclovir for herpes simplex virus infection: long-term safety and sustained efficacy after 20 years' experience with acyclovir. J Infect Dis. 2002.Source linkedPMID
- 9D'Antonio F, Marinceu D, Prasad S et al.. Effectiveness and safety of prenatal valacyclovir for congenital cytomegalovirus infection: systematic review and meta-analysis. Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology. 2023Source linkedPMID
- 10Brandariz-Nuñez D, Correas-Sanahuja M, Maya-Gallego S et al.. Neurotoxicity associated with acyclovir and valacyclovir: A systematic review of cases. Journal of clinical pharmacy and therapeutics. 2021Source linkedPMID
Common questions.
Quick answers about Valacyclovir, drawn from the data on this page.
What is Valacyclovir?
The L-valyl ester prodrug of acyclovir, providing 3-5 times higher oral bioavailability than acyclovir. This allows less frequent dosing (2-3 times daily vs 5 times daily) with equivalent or superior efficacy. Used for genital herpes (initial, recurrent, and suppressive therapy), herpes zoster (shingles), herpes labialis (cold sores), and reduction of HSV transmission to uninfected partners. The preferred oral agent for herpes infections in most clinical scenarios.
What is Valacyclovir used for?
Commonly cited benefits of Valacyclovir include: Treats and suppresses genital herpes (preferred oral agent); Treats herpes zoster (shingles), better bioavailability than acyclovir; Treats herpes labialis (cold sores), 1-day treatment; Reduces transmission of genital HSV-2 to uninfected partners by ~50%; Convenient dosing (2-3 times daily vs 5 times daily for acyclovir). NutriStack rates the overall evidence as strong.
What is a typical dose of Valacyclovir?
A typical adult dose of Valacyclovir is Genital herpes initial: 1 g BID x 10 days; recurrent: 500 mg BID x 3 days; suppressive: 500 mg-1 g daily; herpes zoster: 1 g TID x 7 days; cold sores: 2 g BID x 1 day (as prescribed by your physician). The commonly recommended form is Oral tablets (caplets). These are general ranges, not personalized advice; confirm the right dose with a clinician.
What are the side effects of Valacyclovir?
Reported side effects include headache, nausea, abdominal pain, dizziness, renal impairment (rare, especially with high doses in immunocompromised), thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (ttp/hus, rare, in immunocompromised at high doses). This is educational information; check with a healthcare professional before use.
How strong is the evidence for Valacyclovir?
NutriStack rates this as Strong, meaning multiple high-quality meta-analyses or systematic reviews converge on the same finding. Full tier criteria are at https://nutristackapp.com/methodology/evidence-tiers.
Use this with your stack
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