Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
Quick facts
- How it is given
- oral
- Type
- human prescription drug
- Brand names
- Valacyclovir Hydrochloride
- RxNorm ID
- 313565
We do not publish dosing. How much of this medicine to take, how often, and for how long depends on your age, weight, kidney and liver function, other conditions and other medicines. That is a decision for the person who prescribes or dispenses it. Follow the directions on your own pack and ask your pharmacist if anything is unclear.
What it is used to treat
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 Zoster Pediatric Patients ( 1.2 ) Cold Sores (Herpes Labialis) Chickenpox Limitations of Use ( 1.3 ) The efficacy and safety of valacyclovir tablets have not been established in immunocompromised patients other than for the suppression of genital herpes in HIV-1–infected patients. 1.1 Adult Patients Cold Sores (Herpes Labialis) Valacyclovir tablets are indicated for treatment of cold sores (herpes labialis). The efficacy of valacyclovir tablets initiated after the development of clinical signs of a cold sore (e.g., papule, vesicle, or ulcer) has not been established. Genital Herpes Initial Episode Valacyclovir tablets are indicated for treatment of the initial episode of genital herpes in immunocompetent adults. The efficacy of treatment with valacyclovir tablets when initiated more than 72 hours after the onset of signs and symptoms has not been established. Recurrent Episodes Valacyclovir tablets are indicated for treatment of recurrent episodes of genital herpes in immunocompetent adults. The efficacy of treatment with valacyclovir tablets when initiated more than 24 hours after the onset of signs and symptoms has not been established. Suppressive Therapy Valacyclovir tablets are indicated for chronic suppressive therapy of recurrent episodes of genital herpes in immunocompetent and in HIV-1–infected adults. The efficacy and safety of valacyclovir tablets for the suppression of genital herpes beyond 1 year in immunocompetent patients and beyond 6 months in HIV-1–infected patients have not been established. Reduction of Transmission Valacyclovir tablets are indicated for the reduction of transmission of genital herpes in immunocompetent adults. The efficacy of valacyclovir tablets for the reduction of transmission of genital herpes beyond 8 months in discordant couples has not been established. […]
About this medicine
Valacyclovir hydrochloride is the hydrochloride salt of the L -valyl ester of the antiviral drug acyclovir. Valacyclovir tablets, USP are for oral administration. Each tablet contains 556.2 mg or 1.112 grams of valacyclovir hydrochloride, USP (hydrous), which are equivalent to 500 mg or 1 gram of valacyclovir, on the anhydrous basis, respectively, and the inactive ingredients hypromellose, magnesium stearate, microcrystalline cellulose, polyethylene glycol and titanium dioxide. The white, film-coated tablets are printed with edible black ink which contains black iron oxide, propylene glycol and shellac glaze. The chemical name of valacyclovir hydrochloride is L -valine, 2-[(2-amino-1,6-dihydro-6-oxo-9 H -purin-9-yl)methoxy]ethyl ester, monohydrochloride. It has the following structural formula: Valacyclovir hydrochloride, USP (hydrous) is a white to off-white powder with the molecular formula C 13 H 20 N 6 O 4 •HCl and a molecular weight of 360.80. The maximum solubility in water at 25°C is 174 mg/mL. The pk a s for valacyclovir hydrochloride are 7.47 and 9.43. Meets USP Dissolution Test 2. Valacyclovir Hydrochloride Structural Formula
How it works
12.1 Mechanism of Action Valacyclovir is an antiviral drug active against α-herpes viruses [see Microbiology (12.4) ]. Mechanism of Action Valacyclovir is a deoxynucleoside analogue DNA polymerase inhibitor. Valacyclovir hydrochloride is rapidly converted to acyclovir, which has demonstrated antiviral activity against HSV types 1 (HSV-1) and 2 (HSV-2) and VZV both in cell culture and in vivo. Acyclovir is a synthetic purine deoxynucleoside that is phosphorylated intracellularly by the viral encoded thymidine kinase (TK; pUL23) of HSV or VZV into acyclovir monophosphate, a nucleotide analogue. The monophosphate is further converted into diphosphate by cellular guanylate kinase and into triphosphate by a number of cellular enzymes. In biochemical assays, acyclovir triphosphate inhibits replication of α-herpes viral DNA. This is accomplished in 3 ways: 1) competitive inhibition of viral DNA polymerase, 2) incorporation and termination of the growing viral DNA chain, and 3) inactivation of the viral DNA polymerase. The greater antiviral activity of acyclovir against HSV compared with VZV is due to its more efficient phosphorylation by the viral TK.
Who should not take it
Valacyclovir tablets are contraindicated in patients who have had a demonstrated clinically significant hypersensitivity reaction [e.g., anaphylaxis, severe cutaneous adverse reactions (SCARs)] to valacyclovir, acyclovir, or any component of the formulation [see Warnings and Precautions (5.4) , Adverse Reactions (6.3) ] . Hypersensitivity to valacyclovir (e.g., anaphylaxis), acyclovir, or any component of the formulation. ( 4 )
Warnings and cautions
Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS): Has occurred in patients with advanced HIV-1 disease and in allogenic bone marrow transplant and renal transplant patients receiving 8 grams per day of valacyclovir tablets in clinical trials. Discontinue treatment if clinical symptoms and laboratory findings consistent with TTP/HUS occur. ( 5.1 ) Acute renal failure: May occur in elderly patients (with or without reduced renal function), patients with underlying renal disease who receive higher-than-recommended doses of valacyclovir tablets for their level of renal function, patients who receive concomitant nephrotoxic drugs, or inadequately hydrated patients. Use with caution in elderly patients and reduce dosage in patients with renal impairment. ( 2.4 , 5.2 ) Central nervous system adverse reactions (e.g., agitation, hallucinations, confusion, and encephalopathy): May occur in both adult and pediatric patients (with or without reduced renal function) and in patients with underlying renal disease who receive higher-than-recommended doses of valacyclovir tablets for their level of renal function. Elderly patients are more likely to have central nervous system adverse reactions. Use with caution in elderly patients and reduce dosage in patients with renal impairment. ( 2.4 , 5.3 ) Severe cutaneous adverse reactions (SCARs): Including acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), toxic epidermal necrolysis (TEN), and Stevens-Johnson syndrome (SJS) have been reported during the postmarketing experience with valacyclovir. Discontinue valacyclovir tablets immediately if a painful rash with mucosal involvement or a progressive severe rash develops, and closely monitor clinical status. ( 5.4 ) 5.1 Thrombotic Thrombocytopenic Purpura/Hemolytic Uremic Syndrome (TTP/HUS) TTP/HUS, in some cases resulting in death, has occurred in patients with advanced HIV-1 disease and also in allogeneic bone marrow transplant and renal transplant recipients participating in clinical trials of valacyclovir tablets at doses of 8 grams per day. […]
Reported side effects
The following serious adverse reactions are discussed in greater detail in other sections of the labeling: Thrombotic Thrombocytopenic Purpura/Hemolytic Uremic Syndrome [see Warnings and Precautions (5.1) ]. Acute Renal Failure [see Warnings and Precautions (5.2) ] . Central Nervous System Effects [see Warnings and Precautions (5.3) ] . Severe Cutaneous Adverse Reactions [see Warnings and Precautions (5.4) ] . The most common adverse reactions reported in at least 1 indication by greater than 10% of adult subjects treated with valacyclovir tablets and observed more frequently with valacyclovir tablets compared with placebo are headache, nausea, and abdominal pain. The only adverse reaction reported in greater than 10% of pediatric subjects aged less than 18 years was headache. The most common adverse reactions reported in at least one indication by greater than 10% of adult subjects treated with valacyclovir tablets and more commonly than in subjects treated with placebo are headache, nausea, and abdominal pain. ( 6.1 ) The only adverse reaction occurring in greater than 10% of pediatric subjects aged less than 18 years was headache. ( 6.2 ) To report SUSPECTED ADVERSE REACTIONS, contact Mylan at 1-877-446-3679 (1-877-4-INFO-RX) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience in Adult Subjects Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice. Cold Sores (Herpes Labialis) In clinical trials for the treatment of cold sores, the adverse reactions reported by subjects receiving valacyclovir tablets 2 grams twice daily (n = 609) or placebo (n = 609) for 1 day, respectively, included headache (14%, 10%) and dizziness (2%, 1%). The frequencies of abnormal ALT (greater than 2 x ULN) were 1.8% for subjects receiving valacyclovir tablets compared with 0.8% for placebo. Other laboratory abnormalities (hemoglobin, white blood cells, alkaline phosphatase, and serum creatinine) occurred with similar frequencies in the 2 groups. […]
Interactions with other medicines
No clinically significant drug-drug or drug-food interactions with valacyclovir tablets are known [see Clinical Pharmacology (12.3) ].
Use in specific groups
8.1 Pregnancy 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. There are insufficient data on the use of valacyclovir regarding miscarriage or adverse maternal or fetal outcomes (see Data ) . There are risks to the fetus associated with untreated herpes simplex during pregnancy (see Clinical Considerations ). In animal reproduction studies, no evidence of adverse developmental outcomes was observed with valacyclovir when administered to pregnant rats and rabbits at system exposures (AUC) 4 (rats) and 7 (rabbits) times the human exposure at the maximum recommended human dose (MRHD) (see Data ) . The estimated background risk of major birth defects and miscarriage for the indicated populations is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. Clinical Considerations Disease-Associated Maternal and/or Embryo/Fetal Risk The risk of neonatal HSV infection varies from 30% to 50% for genital HSV acquired in late pregnancy (third trimester), whereas with HSV acquisition in early pregnancy, the risk of neonatal infection is about 1%. A primary herpes occurrence during the first trimester of pregnancy has been associated with neonatal chorioretinitis, microcephaly, and, in rare cases, skin lesions. In very rare cases, transplacental transmission can occur resulting in congenital infection, including microcephaly, hepatosplenomegaly, intrauterine growth restriction, and stillbirth. Co-infection with HSV increases the risk of perinatal HIV transmission in women who had a clinical diagnosis of genital herpes during pregnancy. Data Human Data Clinical data over several decades with valacyclovir and its metabolite, acyclovir, in pregnant women, based on published literature, have not identified a drug-associated risk of major birth defects. […]
If too much is taken
Caution should be exercised to prevent inadvertent overdose [see Use in Specific Populations (8.5 , 8.6) ] . Precipitation of acyclovir in renal tubules may occur when the solubility (2.5 mg/mL) is exceeded in the intratubular fluid. In the event of acute renal failure and anuria, the patient may benefit from hemodialysis until renal function is restored [see Dosage and Administration (2.4) ] .
Before you take anything new
Tell your pharmacist or doctor about every medicine you take — including ones bought without a prescription, herbal products and supplements. Interactions are one of the most common avoidable causes of harm from medicines, and a pharmacist can check your full list in a couple of minutes.
This page is built from the openFDA record of the U.S. Food and Drug Administration's approved labelling for this product, effective 28 May 2026. Label text has been shortened and reformatted for readability; safety wording has not been altered in meaning. FDA labelling describes products approved in the United States — brand names, strengths, formulations and approved uses may differ in your country. Always read the leaflet that comes with your own pack. PocketsInfo is not affiliated with, and is not endorsed by, the FDA. Retrieved 2026-07-30.