Acyclovir Dosing for HSV-1 Infections in Canada
For HSV-1 infections in children, prescribe oral acyclovir 20 mg/kg per dose (maximum 400 mg/dose) three times daily for 5-10 days, and for adults, use 200-400 mg orally five times daily or 800 mg if higher dosing is needed. 1, 2
Pediatric Dosing
Standard Dosing for Children
- Oral acyclovir 20 mg/kg per dose (maximum 400 mg/dose) three times daily for 5-10 days is the CDC-recommended regimen for mild to moderate HSV-1 infections including herpetic gingivostomatitis and eczema herpeticum 1, 2
- Treatment should be initiated within the first 3 days of symptom onset for optimal efficacy 2
- Continue therapy until lesions completely heal 1, 2
Severe Disease in Children
- For moderate to severe disease, switch to intravenous acyclovir 5-10 mg/kg per dose three times daily, then transition to oral acyclovir once lesions begin to regress 1
- Monitor for clinical improvement within 48-72 hours 1, 2
Neonatal HSV Infections
- Neonates require higher doses: IV acyclovir 20 mg/kg every 8 hours for 14 days (skin/eye/mouth disease) or 21 days (CNS disease) 1, 2
- For CNS disease, repeat CSF HSV DNA PCR at days 19-21 and do not stop acyclovir until negative 2
Adult Dosing
Standard Treatment
- Oral acyclovir 200 mg five times daily for 3-5 days is the initial standard dose for immunocompetent adults with HSV-1 infections 3
- If response is poor, increase to 800 mg orally five times daily 3
Severe or Refractory Cases
- If no response after 5-7 days of high-dose oral therapy, switch to alternative agents as IV acyclovir is unlikely to be effective 3
- Obtain cultures and acyclovir susceptibility studies before changing therapy 3
Critical Timing Considerations
- Peak viral replication occurs in the first 24 hours after lesion onset, making early treatment imperative 2
- The effect of acyclovir therapy is maximized by early initiation of treatment, especially in non-primary infections 4
Important Monitoring and Safety
Monitoring Parameters
- Monitor renal function and watch for neutropenia with prolonged acyclovir use 1, 2
- Ensure adequate hydration throughout the treatment course to prevent crystalluria 1, 2
- The most important adverse effect is crystalluria and elevated serum creatinine related to bolus intravenous administration 5
Common Pitfalls to Avoid
- Topical antivirals do not reach the site of viral reactivation and cannot impact the host immune response 2
- Laboratory confirmation is only needed in immunocompromised patients with atypical presentations 2
- Acyclovir therapy does not eliminate latent virus or prevent subsequent recurrences 5, 4