What is the recommended dose of valaciclovir (valacyclovir) for children with encephalitis?

Valaciclovir Dosing in Children with Encephalitis

For children with viral encephalitis, valaciclovir is not the first-line treatment; intravenous acyclovir should be used initially, with valaciclovir potentially considered only after a course of IV therapy in specific circumstances. 1

Initial Treatment Approach

First-Line Treatment

• Intravenous acyclovir is the standard first-line treatment for suspected viral encephalitis in children, not valaciclovir 2, 1
• Dosing for IV acyclovir:
  • Children 3 months-12 years: 500 mg/m² IV every 8 hours 1
  • Neonates: 20 mg/kg IV every 8 hours 1
  • Duration: 14-21 days, with minimum 21 days recommended for children 3 months-12 years due to higher relapse rates 2, 1

Valaciclovir Role and Dosing

Valaciclovir is not FDA-approved for use in children with encephalitis and is not routinely recommended as initial therapy. However, in specific situations where maintaining IV access is problematic after initial IV acyclovir treatment, valaciclovir may be considered 2:

• For children who can take adult dosing (typically adolescents): 1 g orally three times daily 2
• For younger children: Limited data exists, but pharmacokinetic studies suggest:
  • Children ≥3 months: 20 mg/kg three times daily 3
  • Not recommended for infants <3 months due to decreased clearance 3

Important Clinical Considerations

Monitoring Requirements

• Regular renal function monitoring is essential with both acyclovir and valaciclovir 1, 4
• CSF PCR should be repeated at the end of treatment to confirm viral clearance 2, 1
• Adequate hydration is crucial to prevent nephrotoxicity 1

Common Pitfalls to Avoid

1. Using oral valaciclovir as initial therapy instead of IV acyclovir 2, 1
2. Stopping treatment based on a single negative CSF PCR early in the disease course 2
3. Using insufficient treatment duration (less than 14-21 days) 2, 1
4. Failing to adjust dosage for renal impairment 1

Special Populations

• Immunocompromised patients may require longer treatment courses and closer monitoring 2, 1
• Infants <3 months should not receive valaciclovir due to decreased clearance 3

Decision Algorithm for Valaciclovir Use

1. Initial treatment: Always start with IV acyclovir at appropriate weight-based dosing
2. Consider valaciclovir only if:
   • Patient has received at least 10-14 days of IV acyclovir 2
   • IV access is problematic 2
   • Patient is clinically improving
   • Patient can reliably take oral medication
3. Contraindications to valaciclovir:
   • Age <3 months 3
   • Significant renal impairment
   • Inability to maintain adequate hydration
   • Ongoing severe symptoms

While valaciclovir offers better bioavailability than oral acyclovir, the evidence for its use in pediatric encephalitis is limited, and it should only be considered in specific circumstances after an appropriate course of IV acyclovir 2, 3.