What is the pediatric dose of valacyclovir (valacyclovir hydrochloride)?

Pediatric Dosing of Valacyclovir

For chickenpox in children aged 2 to less than 18 years, valacyclovir is dosed at 20 mg/kg three times daily for 5 days (maximum 1 gram per dose), and for cold sores in children aged ≥12 years, the dose is 2 grams twice daily for 1 day taken 12 hours apart. 1

FDA-Approved Pediatric Indications and Dosing

Chickenpox (Varicella)

• 20 mg/kg orally three times daily for 5 days in immunocompetent children aged 2 to less than 18 years 1
• Maximum dose: 1 gram three times daily 1
• Initiate therapy at the earliest sign or symptom 1
• This dosing produces favorable acyclovir blood concentrations and is well tolerated in children 3 months through 11 years of age 2

Cold Sores (Herpes Labialis)

• 2 grams twice daily for 1 day (taken 12 hours apart) for children aged ≥12 years 1
• Initiate at the earliest symptom (tingling, itching, or burning) 1

Off-Label Use in Younger Children

Herpes Zoster (Shingles)

• For older children who can receive adult dosing: 1000 mg three times daily for 7 days 3
• Alternative: oral acyclovir 20 mg/kg (max 800 mg/dose) four times daily for 7-10 days remains the preferred first-line option for most pediatric patients 4, 3

Acute Retinal Necrosis

• Following IV acyclovir (10 mg/kg three times daily for 10-14 days): 1 gram three times daily for 4-6 weeks for children old enough to receive adult dosing 4
• Alternative: oral acyclovir 20 mg/kg for 4-6 weeks 4

Mucocutaneous HSV Infections

• 1 gram twice daily for adults and adolescents with mucocutaneous HSV 4
• No pediatric preparation exists, and data on dosing in children are limited 4
• Could be used by older children able to receive adult dosing 4

Pharmacokinetic Considerations

Age-Related Dosing Adjustments

• Infants <3 months: A dosing recommendation cannot be made due to decreased clearance in this age group 2
• Infants 1-2 months: Mean AUC and Cmax are approximately 60% and 30% higher, respectively, than in older infants receiving the same dose 2
• Children 3 months to 11 years: The 20 mg/kg dose produces effective acyclovir concentrations 2

Bioavailability

• Valacyclovir demonstrates excellent bioavailability (mean 64%) in pediatric patients 5
• Dose proportionality exists across the 10-20 mg/kg dose range 2
• For children 2-5 years, increasing from 20 to 25 mg/kg nearly doubles Cmax and AUC 2

Formulation and Administration

Oral Suspension Preparation

• Valacyclovir oral suspension (25 mg/mL or 50 mg/mL) may be prepared extemporaneously from 500-mg tablets for pediatric patients for whom solid dosage forms are not appropriate 1
• Prepared using VALTREX tablets, cherry flavor, and Suspension Structured Vehicle USP-NF in 100 mL lots 1
• May be given without regard to meals 1

Safety Profile

Tolerability

• Valacyclovir oral suspension is well tolerated in children 2
• Grade 1 nausea and emesis (occurring in five patients) was the only valacyclovir-related toxicity in one study 5
• No clinically significant trends in clinical chemical, hematologic, or urinalysis values from screening to follow-up 2

Important Clinical Caveats

Age Restrictions

• Not recommended for children <2 years for chickenpox treatment because efficacy and safety of acyclovir in this age group have not been established 1
• Not recommended for herpes zoster in children because safety data up to 7 days' duration are not available 1

Renal Function Considerations

• Children with augmented renal clearance (eGFR >250 ml/min/1.73 m²) may require higher doses to achieve therapeutic concentrations 6
• Estimated glomerular filtration rate is significantly associated with acyclovir elimination 6

Therapeutic Drug Monitoring

• Consider therapeutic drug monitoring to refine dosing individually, particularly in immunocompromised patients or those with altered renal function 6
• Target trough concentrations above 0.56 mg/L for HSV and 1.125 mg/L for VZV 6
• Keep peak concentrations below 25 mg/L 6