What is the recommended dosage of valacyclovir (valacyclovir hydrochloride) for a 12-year-old child weighing 30kg with a cold sore (herpes simplex labialis)?

Valacyclovir for Cold Sore in a 12-Year-Old Child (30kg)

For a 12-year-old child with a cold sore, administer valacyclovir 2 grams twice daily for 1 day, taken 12 hours apart, initiated at the earliest symptom (tingling, itching, or burning). 1

FDA-Approved Dosing for Cold Sores in Children ≥12 Years

The FDA label for valacyclovir explicitly approves this indication and dosing for pediatric patients aged 12 years and older, making this the definitive recommendation regardless of weight 1:

• Dose: 2 grams orally twice daily for 1 day (12 hours apart) 1
• Timing: Initiate at the earliest symptom of a cold sore (tingling, itching, burning) 1
• Administration: May be given without regard to meals 1

Formulation Considerations for This Patient

Since this child is 12 years old and weighs 30kg, tablet administration is appropriate 1:

• Valacyclovir is available as 500-mg tablets 1
• For the 2-gram dose, administer four 500-mg tablets per dose 1
• If the child cannot swallow tablets, an extemporaneous oral suspension (25 mg/mL or 50 mg/mL) can be compounded from 500-mg tablets using cherry flavor and Suspension Structured Vehicle USP-NF 1

Pharmacokinetic Support in Pediatric Populations

Research confirms valacyclovir is well-tolerated and achieves therapeutic acyclovir concentrations in children 2, 3:

• Among children 3 months through 11 years of age, valacyclovir oral suspension produces favorable acyclovir blood concentrations 2
• The bioavailability of acyclovir from valacyclovir in pediatric patients is approximately 64%, providing significantly higher exposure than oral acyclovir 3
• Valacyclovir was well tolerated with only Grade 1 nausea and emesis reported in a minority of patients 3

Critical Timing for Maximum Efficacy

Early initiation is essential for optimal outcomes 1:

• Treatment is most effective when started at the first sign of prodromal symptoms (tingling, itching, burning) 1
• Delaying treatment until lesions are fully developed reduces efficacy 1

Common Pitfalls to Avoid

• Do not use adult acyclovir dosing for cold sores in children: The adult acyclovir regimen for cold sores (400 mg five times daily) is not FDA-approved for pediatric cold sores and requires more frequent dosing 1
• Do not extend treatment beyond 1 day: The FDA-approved regimen for cold sores is specifically 1 day of therapy, not the 5-7 day courses used for other herpesvirus infections 1
• Do not confuse with herpes zoster dosing: Herpes zoster requires 1 gram three times daily for 7 days, which is a different indication 1