Overview
Valacyclovir is an antiviral prodrug converted to acyclovir, which inhibits viral DNA replication. It is primarily used for treating herpes simplex virus (HSV) and varicella-zoster virus (VZV) infections, including genital herpes, herpes zoster (shingles), and chickenpox. The medication reduces symptom severity and duration while decreasing viral shedding.
Mechanism of Action
Valacyclovir is rapidly converted to acyclovir by first-pass intestinal and hepatic metabolism. Acyclovir is phosphorylated by viral thymidine kinase to acyclovir triphosphate, which competitively inhibits viral DNA polymerase and incorporates into viral DNA, causing chain termination and inhibition of viral replication.
Indications
- Treatment of herpes zoster (shingles)
- Treatment of genital herpes (initial and recurrent episodes)
- Suppression of recurrent genital herpes
- Treatment of herpes labialis (cold sores)
- Treatment of chickenpox in pediatric patients
Common Doses
- 500 mg
- 1 g
Dosage
Administer orally without regard to meals. Typical adult doses: 1g twice daily for 7 days for herpes zoster, 500mg twice daily for 3-10 days for genital herpes, 500mg-1g once daily for suppression. Pediatric dosing based on weight for chickenpox. Adjust dosage in renal impairment.
Contraindications
- Hypersensitivity to valacyclovir, acyclovir, or any component of the formulation
- History of severe cutaneous adverse reactions (SCARs) or anaphylaxis to valacyclovir or acyclovir
Side Effects
- Headache (most common)
- Nausea
- Abdominal pain
- Dizziness
- Fatigue
- Rash
- Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome
- Acute renal failure
- Central nervous system effects (confusion, hallucinations)
Interactions
- No clinically significant drug-drug or drug-food interactions known
- Potential for increased acyclovir concentrations when co-administered with drugs that reduce renal clearance
Counseling Points
- Take as prescribed, even if symptoms improve
- May take with or without food
- Drink plenty of fluids to maintain hydration
- Report signs of kidney problems (decreased urination, swelling)
- Seek immediate medical attention for severe skin reactions or neurological symptoms
- Use barrier protection during sexual activity to prevent transmission of genital herpes
- Avoid touching herpes lesions and wash hands frequently