Valacyclovir
VALTREX
What it isOrally absorbed prodrug of acyclovir that inhibits viral DNA polymerase; herpes simplex and zoster.
Why this oneFar better oral absorption than acyclovir permits simpler regimens while delivering the same active antiviral.
What limits itReduce in renal impairment or expect neurotoxicity and crystal nephropathy. It shortens episodes rather than eradicating latent virus.
FDA-approved for
- herpes/shingles (1995)
FDA label
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| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Cold sores (herpes labialis) | Adults; peds ≥12 y | 2 g BID ×1 day (12 h apart) | 2 g BID ×1 day | |
| Genital herpes — initial episode | Adults | 1 g BID ×10 days | 1 g BID | |
| Genital herpes — recurrent | Adults | 500 mg BID ×3 days | 500 mg BID | |
| Genital herpes — suppressive | Immunocompetent | 1 g QD (500 mg QD if ≤9 recurrences/yr) | 1 g QD | |
| Genital herpes — suppressive | HIV-1, CD4 ≥100 | 500 mg BID | 500 mg BID | |
| Reduction of transmission | Immunocompetent | 500 mg QD | 500 mg QD | |
| Herpes zoster | Adults | 1 g TID ×7 days | 1 g TID | |
| Chickenpox | Peds 2 to <18 y | 20 mg/kg TID ×5 days | 20 mg/kg TID | 1 g TID |
Renal Dose reduction required in renal impairment (adjust per creatinine clearance).
Hepatic Undefined
Instructions
- May be given without regard to meals
- Oral suspension (25 or 50 mg/mL) may be compounded from 500-mg tablets for pediatric use
Cautions
- TTP/HUS at 8 g/day in advanced HIV-1 and transplant patients
- Acute renal failure (elderly, renal disease, dehydration, nephrotoxic drugs, overdosing for renal function)
- CNS reactions (agitation, hallucinations, confusion, encephalopathy)
- Severe cutaneous adverse reactions (AGEP, DRESS, TEN, SJS)
Adverse reactions
- Headache
- Nausea
- Abdominal pain
Pregnancy Decades of data show no drug-associated risk of major birth defects; insufficient data on miscarriage.
Lactation Acyclovir present in human milk; weigh benefits against clinical need.
NO BOXED WARNINGS
Principal riskNeurotoxicity and crystal nephropathy if renal dose is not reduced
Cost, est. cash$10–$500/month
Generic entry2007
Classes and tags
Clinical profile
Legacy pregnancy categoryB
Defining liabilityAgent-specific renal, hepatic, hematologic, metabolic and drug-interaction toxicity.
Active metabolites
Mechanism of action: Valacyclovir ballicule
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Memory aids: mascots and interaction avatars
prodrug of acyclovir