Valacyclovir (Valtrex) Dosing for Viral Infections
The recommended dosing of valacyclovir varies by indication, with specific regimens for cold sores (2g twice daily for 1 day), genital herpes (500mg-1g based on episode type), and herpes zoster (1g three times daily for 7 days). 1
Adult Dosing by Indication
Cold Sores (Herpes Labialis)
- 2 grams twice daily for 1 day (taken 12 hours apart)
- Initiate at earliest symptom (tingling, itching, or burning)
Genital Herpes
- Initial Episode: 1 gram twice daily for 10 days
- Most effective when started within 48 hours of symptom onset
- Recurrent Episodes: 500 mg twice daily for 3 days
- Initiate at first sign of episode
- Suppressive Therapy:
- Normal immune function: 1 gram once daily
- Alternative for ≤9 recurrences/year: 500 mg once daily
- HIV-infected patients (CD4+ ≥100 cells/mm³): 500 mg twice daily
- Transmission Reduction: 500 mg once daily for source partner
Herpes Zoster (Shingles)
- 1 gram 3 times daily for 7 days
- Initiate at earliest sign of herpes zoster
- Most effective when started within 48 hours of rash onset
Pediatric Dosing
Cold Sores
- Children ≥12 years: 2 grams twice daily for 1 day (12 hours apart)
Chickenpox
- Children 2 to <18 years: 20 mg/kg 3 times daily for 5 days
- Maximum dose: 1 gram 3 times daily
Dosage Adjustments for Renal Impairment
Creatinine clearance 30-49 mL/min:
- Cold sores: No reduction
- Genital herpes (recurrent): No reduction
- Genital herpes (suppressive): No reduction
- Herpes zoster: 1 gram every 12 hours
Creatinine clearance 10-29 mL/min:
- Cold sores: 1 gram every 24 hours
- Genital herpes (recurrent): 500 mg every 24 hours
- Genital herpes (suppressive): 500 mg every 24 hours
- Herpes zoster: 1 gram every 24 hours
Creatinine clearance <10 mL/min:
- Cold sores: 500 mg every 24 hours
- Genital herpes (recurrent): 500 mg every 24 hours
- Genital herpes (suppressive): 500 mg every 24 hours
- Herpes zoster: 500 mg every 24 hours
Special Considerations
Hemodialysis Patients
- Administer recommended dose after hemodialysis
- Approximately one-third of acyclovir is removed during a 4-hour hemodialysis session
Peritoneal Dialysis
- No supplemental doses required following CAPD or CAVHD
Clinical Pearls
- Valacyclovir may be given without regard to meals 1
- Oral suspension (25 mg/mL or 50 mg/mL) can be prepared from 500-mg tablets for pediatric patients 1
- Valacyclovir provides significantly better oral bioavailability than oral acyclovir, allowing for less frequent dosing 2
- For genital herpes suppression, valacyclovir 500 mg once daily has been shown to prevent or delay 85% of recurrences compared to placebo 3
- In immunocompromised patients receiving high-dose valacyclovir (8 g/day) for prolonged periods, monitor for thrombotic microangiopathy (TMA)-like syndrome 2
Efficacy Considerations
- Valacyclovir is at least as effective as acyclovir for herpes zoster and significantly faster in alleviating zoster-associated pain 4
- For genital herpes, valacyclovir (500 mg to 1000 mg twice daily) is as effective as acyclovir (200 mg 5 times daily) 5
- Once-daily valacyclovir (500 mg) provides a more convenient dosing regimen than more frequent acyclovir regimens with comparable efficacy 3
Remember to initiate treatment as early as possible after symptom onset for optimal efficacy, particularly within 48 hours for herpes zoster and at the earliest symptom for cold sores.