Recommended Dosage of Valtrex (Valacyclovir) for Viral Infections
Valacyclovir dosing varies by specific viral infection type, with 500-1000 mg twice daily being the most common regimen for herpes simplex virus infections and 1 gram three times daily for herpes zoster infections. 1, 2
Herpes Simplex Virus (HSV) Infections
First Clinical Episode of Genital Herpes
- Valacyclovir 1 gram orally twice daily for 7-10 days 1, 2
- Treatment is most effective when initiated within 48 hours of symptom onset 1
- Treatment may be extended if healing is incomplete after 10 days 2
Recurrent Episodes of Genital Herpes
- Valacyclovir 500 mg orally twice daily for 3 days 1, 2
- Alternative shorter regimen: 500 mg twice daily for 3 days has been shown to be as effective as a 5-day course 3
- Treatment should be initiated at the first sign or symptom of an episode 1
Suppressive Therapy for Recurrent Genital Herpes
- For patients with normal immune function: 1 gram once daily 1, 2
- For patients with 9 or fewer recurrences per year: 500 mg once daily 1, 4
- For HIV-infected patients with CD4+ count ≥100 cells/mm³: 500 mg twice daily 1
- For reduction of transmission: 500 mg once daily for the source partner 1
Cold Sores (Herpes Labialis)
- Adults and children ≥12 years: 2 grams twice daily for 1 day taken 12 hours apart 1
- Therapy should be initiated at the earliest symptom (tingling, itching, or burning) 1
Varicella-Zoster Virus (VZV) Infections
Herpes Zoster (Shingles)
- Valacyclovir 1 gram orally three times daily for 7 days 1, 2
- Alternative higher-dose regimen: 1.5 grams twice daily for 7 days has been shown to be effective 5
- Therapy should be initiated at the earliest sign of herpes zoster and is most effective when started within 48 hours of rash onset 1
- For persistent or recalcitrant VZV conjunctivitis: 1000 mg every 8 hours for 7 days 2
Chickenpox
- For immunocompetent pediatric patients 2 to <18 years: 20 mg/kg three times daily for 5 days (not to exceed 1 gram three times daily) 1
Special Populations
Immunocompromised Patients
- For HSV infections in HIV-infected patients: 500 mg twice daily for suppressive therapy 1, 2
- For acute retinal necrosis: IV acyclovir 10 mg/kg three times daily for 10-14 days, followed by oral valacyclovir 1 gram three times daily for 4-6 weeks 2
- Caution: High-dose valacyclovir (8 g/day) has been associated with thrombotic microangiopathy in immunocompromised patients 6
Renal Impairment
- Dosage adjustment is required for patients with reduced renal function 1
- Close monitoring is recommended for immunocompromised patients receiving high-dose therapy 6
Clinical Pearls and Pitfalls
- Valacyclovir has significantly better oral bioavailability than acyclovir, allowing for less frequent dosing 7
- Therapy is most effective when initiated within the first 48-72 hours of symptom onset 1, 5
- For herpes zoster, valacyclovir has been shown to reduce the duration of zoster-associated pain compared to acyclovir 7
- Daily suppressive therapy reduces genital herpes recurrences by ≥75% among patients with frequent recurrences 2, 4
- Valacyclovir may be taken without regard to meals 1
- Common side effects include headache and gastrointestinal disturbances 6
- Suppressive therapy does not eliminate asymptomatic viral shedding, so the risk of transmission remains 2
Remember that early initiation of therapy is crucial for optimal outcomes in both HSV and VZV infections 1, 5.