Pediatric Dosing of Valtrex for Cold Sores
For pediatric patients aged 12 years and older with cold sores, administer valacyclovir 2 grams twice daily for 1 day, taken 12 hours apart, initiated at the earliest symptom (tingling, itching, or burning). 1
Age-Specific Dosing
- Children ≥12 years: The FDA-approved dose is 2 grams twice daily for 1 day (total of 2 doses, 12 hours apart) 1
- Children <12 years: Valacyclovir is not FDA-approved for cold sores in this age group 1
Alternative for Younger Children
For children under 12 years who cannot receive valacyclovir, oral acyclovir remains the treatment option at 20 mg/kg per dose (maximum 400 mg/dose) three times daily for 5-10 days 2. This represents the standard approach for mucocutaneous HSV infections in younger pediatric patients, though it requires more frequent dosing and has lower bioavailability compared to valacyclovir 3.
Timing of Initiation
Treatment must begin at the very first symptom (tingling, itching, burning, or prodromal sensation) to achieve maximum efficacy 1. Delaying treatment beyond the prodromal phase significantly reduces effectiveness, as demonstrated in adult trials where early initiation reduced episode duration by approximately 1 day 4.
Formulation Considerations
- Adolescents ≥12 years: Use standard 500 mg tablets (4 tablets per dose) 1
- Younger children requiring liquid: An extemporaneously compounded oral suspension (25 mg/mL or 50 mg/mL) can be prepared from 500 mg tablets, though this is primarily studied for other HSV indications 1, 3
Important Caveat on Compounded Suspension
While the FDA label describes preparation of valacyclovir oral suspension, the cold sores indication is only approved for children ≥12 years using tablets 1. The suspension formulation has been studied in children as young as 1 month for other herpesvirus infections, showing that 20 mg/kg produces favorable acyclovir concentrations in children 3 months through 11 years 3. However, infants <3 months show decreased clearance and higher drug exposure, making dosing recommendations unsafe in this age group 3.
Renal Dosing Adjustments
No dosage adjustment is needed for cold sores in pediatric patients with normal renal function 1. However, the FDA label does not provide specific renal dosing for the 1-day cold sore regimen in children, only noting that data are unavailable for pediatric patients with creatinine clearance <50 mL/min/1.73 m² 1.
Common Pitfalls to Avoid
- Do not use valacyclovir for cold sores in children <12 years as this is off-label and lacks safety/efficacy data for this specific indication 1
- Do not delay treatment waiting for full lesion development; the 1-day regimen only works when started during prodrome 1, 4
- Do not confuse dosing regimens: The 2 grams twice daily for 1 day cold sore regimen differs completely from the 20 mg/kg three times daily for 5 days chickenpox regimen 1
- Do not extend therapy beyond 1 day for the cold sore indication, as the evidence supports only the single-day, high-dose regimen 4