Dosing & Uses
Dosage Forms & Strengths
tablet
- 500mg
- 1g
Herpes Labialis
2 g PO q12hr for 1 day
Herpes Zoster
1 g PO q8hr for 7 days (no data on efficacy if started 72 hours after rash)
Genital Herpes
Initial episode: 1 g PO q12hr for 10 days
Recurrent episodes: 500 mg PO q12hr for 3 days (no data on efficacy if started >24 hours after lesion onset)
Suppressive therapy (immunocompetent patients): 1 g/day PO
Suppressive therapy (immunocompetent patients with ≤9 recurrences annually): 500 mg/day PO; transmission reduction for source partner, 500 mg/day PO
Suppressive therapy (HIV-infected patients): 500 mg PO q12hr
Dosing Modifications
Herpes labialis
- CrCl 30-49 mL/min: 1 g PO q12hr for 1 day
- CrCl 10-29 mL/min: 500 mg PO q12hr for 1 day
- CrCl <10 mL/min: 500 mg PO once
Herpes zoster
- CrCl 30-49 mL/min: 1 g PO q12hr
- CrCl 10-29 mL/min: 1 g/day PO
- CrCl <10 mL/min: 500 mg/day PO
Genital herpes (initial episode)
- CrCl 10-29 mL/min: 1 g/day PO
- CrCl <10 mL/min: 500 mg/day PO qDay
Genital herpes (recurrent episodes)
- CrCl ≤29 mL/min: 500 mg/day PO
Genital herpes (suppressive therapy, immunocompetent patients)
- CrCl ≤29 mL/min: 500 mg/day PO
Genital herpes (suppressive therapy, immunocompetent patients with ≥9 recurrences annually)
- CrCl ≤29 mL/min: 500 mg PO q48hr
Genital herpes (suppressive therapy, HIV-infected patients)
- CrCl ≤29 mL/min: 500 mg/day PO
Dosage Forms & Strengths
tablet
- 500mg
- 1g
Chickenpox
<2 years: Safety and efficacy not established
>2 years: 20 mg/kg PO q8hr for 5 days; not to exceed 1 g PO q8hr
Herpes Labialis
<12 years: Safety and efficacy not established
>12 years: 2 g PO q12hr for 1 day
Monitor renal function; dosage may have to be adjusted, depending on renal status
Interactions
Interaction Checker
No Results

Contraindicated
Serious - Use Alternative
Significant - Monitor Closely
Minor

Adverse Effects
>10%
Headache (14-35%)
Neutropenia (<18%)
Elevated aspartate transaminase (AST) (2-16%)
Nasopharyngitis (<16%)
Nausea (6-15%)
Elevated alanine transaminase (ALT) (<14%)
Abdominal pain (2-11%)
1-10%
Dysmenorrhea (1-8%)
Depression (<7%)
Arthralgia (<1-6%)
Vomiting (<1-6%)
Dizziness (2-4%)
Rash (≤8%)
Rhinorrhea (<2%)
Thrombocytopenia (<3%)
Leukopenia (≤1%)
<1%
Agitation
Aggression
Alopecia
Confusion
Erythema multiforme
Hypertension
Tachycardia
Tremor
Visual disturbances
Warnings
Contraindications
Hypersensitivity to valacyclovir or acyclovir
Cautions
Thrombotic thrombocytopenic purpura (TTP)/hemolytic uremic syndrome (HUS) reported in patients with advanced HIV disease and in allogenic bone marrow transplant and renal transplant recipients
Acute renal failure (ARF) may occur, especially in elderly patients or those with underlying renal impairment receiving higher than recommended doses; use with caution in patients with renal impairment, the elderly, and/or patients receiving nephrotoxic drugs
Treatment should begin with the earliest symptom (tingling, burning, itching) in cold sores; for genital herpes, it should begin at the first signs and symptoms (within 72 hours of onset of first diagnosis or 24 hours of onset of recurrent episodes); for herpes zoster, it should begin within 72 hours of onset of rash; for chicken pox, it should begin with the earliest sign or symptom
Central nervous system (CNS) effects may occur (eg, agitation, hallucinations, confusion, encephalopathy); risk of CNS adverse effects is higher in elderly patients
Adequately hydrate patient; decreased precipitation in renal tubules may occur
Pregnancy & Lactation
Pregnancy
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 use of valacyclovir regarding miscarriage or adverse maternal or fetal outcomes; there are risks to fetus associated with untreated herpes simplex during pregnancy
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, risk of neonatal infection is about 1%; a primary herpes occurrence during 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 risk of perinatal HIV transmission in women who had a clinical diagnosis of genital herpes during pregnancy
Animal data
- 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 human exposure at maximum recommended human dose (MRHD)
Lactation
Although there is no information on presence of drug in human milk, its metabolite, acyclovir, is present in human milk following oral administration of drug; based on published data, a 500-mg maternal dose twice daily would provide a breastfed child with an oral acyclovir dosage of approximately 0.6 mg/kg/day; there is no data on effects of drug on breastfed child or on milk production
Consider developmental and health benefits of breastfeeding along with mother’s clinical need for therapy and any potential adverse effects on breastfed child from drug or from underlying maternal condition
Pregnancy Categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk. C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done. D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk. X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist. NA: Information not available.Pharmacology
Mechanism of Action
Converted to acyclovir by intestinal and hepatic metabolism
Competes with deoxyguanosine triphosphate for viral DNA polymerase to inhibit DNA synthesis and viral replication
Absorption
Rapidly absorbed
Bioavailability: ~55% (after conversion to acyclovir)
Distribution
Acyclovir (active drug) is widely distributed throughout the body, including brain, kidney, muscle, uterus, lungs, liver, spleen, vagina, and cerebrospoinal fluid (CSF)
Protein bound: 13.5-17.9%
Metabolism
Metabolized by liver; valacyclovir is rapidly and nearly completely converted to acyclovir and L-valine via first-pass effect; acyclovir is hepatically metabolized to a very small extent by aldehyde oxidase and by alcohol and aldehyde dehydrogenase (inactive metabolites)
Elimination
Half-life (normal renal function, adults): Acyclovir, 2.5-3.3 hr; valacyclovir, ~30 min
Half-life (end-stage renal disease): Acyclovir, 14-20 hr
Excretion: Urine (89%), feces (minimal)
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Formulary
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