What is the recommended dose of valacyclovir (Valtrex) for a 12-year-old patient with oral herpes, weighing 43.6kg?

Valacyclovir Dosing for Oral Herpes in a 12-Year-Old, 43.6kg Patient

For a 12-year-old patient weighing 43.6kg with oral herpes (herpes labialis/cold sores), the recommended dose of valacyclovir is 2 grams twice daily for 1 day, taken 12 hours apart, initiated at the earliest symptom. 1

FDA-Approved Pediatric Dosing

• The FDA label explicitly states that for cold sores in pediatric patients aged ≥12 years, the dosage is 2 grams twice daily for 1 day (total of 2 doses separated by 12 hours). 1

• This patient at 43.6kg and 12 years of age meets both the age and weight criteria for adult dosing of valacyclovir for herpes labialis. 1

• Therapy should be initiated at the earliest symptom of a cold sore (tingling, itching, or burning) for maximum efficacy. 1

Alternative Treatment if Valacyclovir is Unavailable

• If valacyclovir cannot be used, oral acyclovir is the alternative at 20 mg/kg per dose (maximum 400 mg/dose) three times daily for 5-10 days. 2, 3

• For this 43.6kg patient, the acyclovir dose would be calculated as 20 mg/kg × 43.6kg = 872mg, but this exceeds the maximum of 400mg/dose, so the dose would be capped at 400mg three times daily. 3

Administration Considerations

• Valacyclovir may be given without regard to meals. 1

• Ensure adequate hydration throughout the treatment course. 4

• The medication does not eradicate latent virus or affect the risk of future recurrences. 4

Renal Function Monitoring

• For patients with normal renal function (creatinine clearance ≥50 mL/min), no dose adjustment is needed. 1

• If renal impairment is present, dosage adjustments are required based on creatinine clearance, though data are limited for pediatric patients with creatinine clearance <50 mL/min/1.73m². 1

Clinical Pearls

• The short 1-day course of valacyclovir (2 doses total) offers superior compliance compared to the 5-10 day course required for acyclovir. 2

• Early initiation is critical—treatment is most effective when started within the first 24-48 hours of symptom onset. 1, 5

• Monitor for clinical improvement, though with oral herpes the brief treatment course typically shows rapid resolution of symptoms. 5