3.3 (1)
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More about Valacyclovir

What is/are Valacyclovir?

Valaciclovir (INN) or valacyclovir (USAN) is an antiviral drug used in the management of herpes simplex, herpes zoster (shingles), and herpes B. It is a prodrug, being converted in vivo to aciclovir. It is marketed by GlaxoSmithKline under the trade names Valtrex and Zelitrex. Valaciclovir has been available as a generic drug in the U.S. since November 25, 2009.

Medical uses


Valtrex brand valaciclovir 500mg tablets

Valaciclovir is indicated for the treatment of HSV and VZV infections, including:

  •     Oral and genital herpes simplex (treatment and prophylaxis)
  •     Reduction of HSV transmission from people with recurrent infection to uninfected individuals
  •     Herpes zoster (shingles): the typical dosage for treatment of herpes is 1,000mg orally three times a day for seven consecutive days.
  •    Prevention of CMV disease following organ transplantation
  •    Prophylaxis against herpesviruses in immunocompromised patients (such as patients undergoing cancer chemotherapy)

It has shown promise as a treatment for infectious mononucleosis, and is preventively administered in suspected cases of herpes B virus exposure.

Adverse effects

Common adverse drug reactions (≥1% of patients) associated with valaciclovir therapy are the same as for aciclovir, its active metabolite, and include: nausea, vomiting, diarrhea and headache. Infrequent adverse effects (0.1–1% of patients) include: agitation, vertigo, confusion, dizziness, edema, arthralgia, sore throat, constipation, abdominal pain, rash, weakness and/or renal impairment. Rare adverse effects (<0.1% of patients) include: coma, seizures, neutropenia, leukopenia, tremor, ataxia, encephalopathy, psychotic symptoms, crystalluria, anorexia, fatigue, hepatitis, Stevens–Johnson syndrome, toxic epidermal necrolysis and/or anaphylaxis.

Mechanism of action

Valaciclovir is a prodrug, an esterified version of aciclovir that has greater oral bioavailability (about 55%) than aciclovir (10–20%). It is converted by esterases to the active drug aciclovir, as well as the amino acid valine, via hepatic first-pass metabolism. Aciclovir is selectively converted into a monophosphate form by viral thymidine kinase, which is far more effective (3000 times) in phosphorylation of aciclovir than cellular thymidine kinase. Subsequently, the monophosphate form is further phosphorylated into the active triphosphate form, aciclo-GTP, by cellular kinases. Aciclo-GTP is a very potent inhibitor of viral DNA polymerase; it has approximately 100 times higher affinity to viral than cellular polymerase. Its monophosphate form also incorporates into the viral DNA, resulting in chain termination. It has also been shown that the viral enzymes cannot remove aciclo-GMP from the chain, which results in inhibition of further activity of DNA polymerase. Aciclo-GTP is fairly rapidly metabolised within the cell, possibly by cellular phosphatases.


Aciclovir, the active metabolite of valaciclovir, is active against most species in the herpesvirus family. In descending order of activity:

  •     Herpes simplex virus type I (HSV-1)
  •     Herpes simplex virus type II (HSV-2)
  •     Varicella zoster virus (VZV)
  •     Epstein–Barr virus (EBV)
  •     Cytomegalovirus (CMV)

The drug is predominantly active against HSV, and to a lesser extent VZV. It is only of limited efficacy against EBV and CMV; however, valacyclovir has recently been shown to lower or eliminate the presence of the Epstein–Barr virus in subjects afflicted with acute mononucleosis, leading to a significant decrease in the severity of symptoms. It is inactive against latent viruses in nerve ganglia.

To date, resistance to valaciclovir has not been clinically significant. Mechanisms of resistance in HSV include deficient viral thymidine kinase, and mutations to viral thymidine kinase and/or DNA polymerase, altering substrate sensitivity.

It also is used for herpes B virus postexposure prophylaxis.

Ingredients and dosage

Valtrex is offered in 500 mg and 1 gram tablets, the active ingredient being valacyclovir hydrochloride, with the inactive ingredients carnauba wax, colloidal silicon dioxide, crospovidone, FD&C Blue No. 2 Lake, hypromellose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polysorbate 80, povidone, and titanium dioxide.

This article uses material from the Wikipedia article Valacyclovir, which is released under the Creative Commons Attribution-Share-Alike License 3.0.

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Medicine containing Valtrex

Medicine containing Valacyclovir

This page uses publicly available data from the U.S. National Library of Medicine (NLM), National Institutes of Health, Department of Health and Human Services; NLM is not responsible for the page and product and does not endorse or recommend this or any other product.

Reviews for Valacyclovir

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Lack of side effects
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Lack of side effects
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Overall satisfaction
Lack of side effects
I am still getting new lesions that itch and swell

After 11 days starting with large dosage 5 days then 1 x day I have not had relief. I am still getting new lesions that itch and swell.

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Herpes Simplex Labialis

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