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ANTIINFECTIVES FOR SYSTEMIC USE › ANTIVIRALS FOR SYSTEMIC USE › DIRECT ACTING ANTIVIRALS › Nucleosides and nucleotides excl. reverse transcriptase inhibitors
valaciclovir
J05AB11
Forms & Strengths
- Oral tablet: 500 mg
- Oral tablet: 1000 mg
Adult Dosing
- Herpes zoster (shingles): 1000 mg PO TID for 7 days
- Genital herpes (initial episode): 1000 mg PO BID for 10 days
- Genital herpes (recurrence): 500 mg PO BID for 3 days
- Genital herpes (suppression): 500 mg or 1000 mg PO once daily
- Herpes labialis (cold sores): 2000 mg PO BID for 1 day
Pediatric Dosing
- Varicella (children 2 to <18 years): 20 mg/kg PO TID (max 1000 mg/dose) for 5 days
- Cold sores (children ≥12 years): 2000 mg PO BID for 1 day
- Herpes zoster, genital herpes safety and efficacy not established in pediatric patients <12 years
Indications
- Treatment of herpes zoster (shingles)
- Treatment and suppression of genital herpes
- Treatment of herpes labialis (cold sores)
- Varicella (chickenpox) in pediatric patients
Mechanism of Action
- Valaciclovir is rapidly and almost completely converted to acyclovir, which is phosphorylated by viral thymidine kinase to acyclovir triphosphate.
- Acyclovir triphosphate competitively inhibits viral DNA polymerase and incorporates into viral DNA, resulting in chain termination and inhibition of viral replication.
Contraindications
- Hypersensitivity to valaciclovir, acyclovir, or any component of the formulation
Adverse Reactions
- Headache
- Nausea
- Abdominal pain
- Vomiting
- Dizziness
- Fatigue
- Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS in immunocompromised patients)
- Acute kidney injury
- Neurotoxicity (confusion, hallucinations, encephalopathy)
Drug Interactions
- Foscarnet: increased risk of severe central nervous system toxicity
- Mycophenolate mofetil: concurrent use may increase concentrations of acyclovir and mycophenolate metabolite
- Nephrotoxic drugs (e.g., aminoglycosides, NSAIDs): increased risk of renal dysfunction
Curated Content: Needs Vetting Before Put to Clinical Use