Valtrex Dosing for Herpes Prophylaxis
For immunocompetent patients with infrequent recurrences (<10 episodes/year), use valacyclovir 500 mg once daily; for those with frequent recurrences (≥10 episodes/year), use 1000 mg once daily. 1, 2
Standard Dosing by Recurrence Frequency
Immunocompetent Patients:
- <10 recurrences per year: 500 mg once daily 1, 2, 3
- ≥10 recurrences per year: 1000 mg once daily (or 250 mg twice daily as alternative) 1, 2, 4
- The 500 mg once-daily dose is less effective in patients with very frequent recurrences and should be avoided in this population 1, 4
HIV-Infected Patients:
- CD4+ count ≥100 cells/mm³: 500 mg twice daily (not once daily) 1, 2, 3
- This higher dosing is necessary due to potentially more severe and frequent recurrences in immunocompromised patients 1, 5
Clinical Efficacy and Duration
- Daily suppressive therapy reduces recurrence frequency by ≥75% among patients with frequent episodes 1, 2
- Safety and efficacy documented for up to 1 year of continuous use with valacyclovir 1, 2
- After 1 year of continuous therapy, discuss discontinuation to reassess recurrence frequency, as recurrences may decrease over time 1, 2
Critical Safety Considerations
Avoid High-Dose Regimens in Immunocompromised Patients:
- Do not use 8 grams per day in immunocompromised patients due to risk of thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS) 1, 5, 6
- TTP/HUS has been reported in HIV-infected patients on high-dose valacyclovir but has not been reported at standard suppressive doses 1, 2
Renal Considerations:
- No dose adjustment needed for CrCl 30-49 mL/min 1
- No laboratory monitoring required unless substantial renal impairment exists 1, 2
- Advise adequate hydration to minimize nephrotoxicity risk 1
Important Counseling Points
- Suppressive therapy reduces but does not eliminate asymptomatic viral shedding 1, 2, 5
- Transmission to sexual partners remains possible despite therapy 2
- For reduction of transmission specifically, the FDA-approved dose is 500 mg once daily for the source partner with ≤9 recurrences per year 3
Treatment Failure Management
If lesions persist after 7-10 days of appropriate therapy:
- Suspect HSV resistance 1, 2, 5
- All acyclovir-resistant strains are also resistant to valacyclovir 1, 5
- Switch to IV foscarnet 40 mg/kg every 8 hours until clinical resolution 1, 2, 5
Common Pitfall to Avoid
Do not prescribe 500 mg once daily for HIV-infected patients—they require 500 mg twice daily for adequate suppression 2, 3. The once-daily regimen is insufficient in this immunocompromised population.