Acyclovir Dosing Guidelines for Pediatric HSV Infections

Intravenous Dosing

CNS or disseminated disease: Administer acyclovir 20 mg/kg intravenously every 8 hours for a total of 21 days. [MMWR Recommendations] [2]
Skin, eye, or mouth disease: Administer acyclovir 20 mg/kg intravenously every 8 hours for a total of 14 days. [MMWR Recommendations] [4]
Therapeutic monitoring: Repeat cerebrospinal fluid HSV DNA PCR between days 19‑21 of therapy and continue acyclovir until the PCR result is negative. [MMWR Recommendations] [5]

CNS or disseminated disease: Administer acyclovir 10 mg/kg intravenously every 8 hours for 21 days. [MMWR Recommendations] [6]
Alternative weight‑based regimen: 500 mg/m² intravenously every 8 hours (equivalent exposure). [MMWR Recommendations] [6]
Moderate to severe gingivostomatitis: Give acyclovir 5‑10 mg/kg intravenously every 8 hours until oral lesions regress, then switch to oral therapy. [MMWR Recommendations] [7]

British pediatric guidelines advise a minimum of 21 days of intravenous acyclovir for children aged 3 months‑12 years, citing relapse rates up to 29 % when treatment is shorter. [Journal of Infection] [8]

Mucocutaneous HSV (children < 45 kg): 20 mg/kg orally (maximum 400 mg per dose) three times daily for 5‑14 days. [MMWR Recommendations] [9]
Mild gingivostomatitis: Same dosing (20 mg/kg orally, max 400 mg) three times daily for 5‑10 days. [MMWR Recommendations] [4]
Genital herpes (children < 45 kg): Same dosing (20 mg/kg orally, max 400 mg) three times daily for 5‑14 days. [MMWR Recommendations] [3]

Nephrotoxicity prevention: Ensure adequate hydration throughout intravenous therapy and monitor renal function regularly; reversible nephropathy occurs in up to 20 % of patients, typically after 4 days of treatment. [Journal of Infection] [8]
Hematologic toxicity: Neutropenia is observed in up to 46 % of neonates receiving long‑term oral suppressive acyclovir, but it is usually self‑limited. [MMWR Recommendations] [10]

Foscarnet regimen: 40 mg/kg intravenously every 8 hours or 60 mg/kg intravenously every 12 hours. [MMWR Recommendations] [2]
Administration precautions: Infuse foscarnet slowly over 2 hours with saline fluid loading to reduce renal toxicity. [MMWR Recommendations] [11]
Renal dose adjustment: Modify foscarnet dosing according to the degree of renal insufficiency. [MMWR Recommendations] [11]

Valacyclovir: Approved for adults/adolescents at 1 g orally twice daily; no pediatric formulation or dosing data are available. [MMWR Recommendations] [6]
Famciclovir: Approved for adults at 500 mg orally twice daily; pediatric preparation and dosing data are lacking. [MMWR Recommendations] [4]