What is the recommended dose of acyclovir (antiviral medication) for pediatric patients with herpes simplex virus infections and normal renal function?

Acyclovir Pediatric Dosing for Herpes Simplex Virus Infections

Recommended Dosing by Clinical Presentation

For mild mucocutaneous HSV infections (including gingivostomatitis and genital herpes) in children with normal renal function, use oral acyclovir 20 mg/kg per dose (maximum 400 mg/dose) three times daily for 5-10 days. 1, 2, 3

Oral Acyclovir Dosing

Mild symptomatic disease (gingivostomatitis, genital herpes):

• 20 mg/kg per dose orally three times daily (maximum 400 mg/dose) 1, 2, 3
• Duration: 5-10 days, continuing until lesions completely heal 1, 3
• Must be initiated within first 3 days of symptom onset for optimal efficacy 3

For children <45 kg: Use the weight-based dosing of 20 mg/kg three times daily 1

For adolescents and adults: 400 mg orally twice daily for 5-14 days 1

Intravenous Acyclovir Dosing

Moderate to severe gingivostomatitis:

• 5-10 mg/kg IV every 8 hours 1, 2
• After lesions begin to regress, transition to oral acyclovir and continue until complete healing 1, 2

CNS or disseminated HSV disease (non-neonatal):

• 10 mg/kg IV every 8 hours for 21 days 1
• Some experts use body surface area dosing: 500 mg/m² IV every 8 hours for children >1 year 1

Neonatal HSV infections require higher doses:

• 20 mg/kg IV every 8 hours 1, 2, 3
• Duration: 14 days for skin/eye/mouth disease; 21 days for CNS or disseminated disease 1, 2, 3
• For neonatal CNS disease, repeat CSF HSV DNA PCR at days 19-21 and do not discontinue acyclovir until negative 1, 3

Dosing Adjustments for Special Populations

Children with augmented renal clearance (eGFR >250 ml/min/1.73 m²):

• May require 15-20 mg/kg IV every 6 hours to achieve therapeutic concentrations 4

Children with impaired baseline renal function:

• Dose reduction required based on creatinine clearance 5
• These patients are at higher risk for nephrotoxicity 5

Critical Monitoring Parameters

Renal function surveillance:

• Monitor serum creatinine before and during therapy 2, 3, 5
• Ensure adequate hydration throughout treatment to minimize nephrotoxicity risk 2, 3
• Concomitant nephrotoxic drugs significantly increase risk of renal injury 5

Hematologic monitoring:

• Watch for neutropenia with prolonged acyclovir use 2, 3

Clinical response assessment:

• Expect clinical improvement within 48-72 hours 2, 3
• If no improvement, consider acyclovir resistance 1, 3

Management of Acyclovir-Resistant HSV

For acyclovir-resistant infections:

• Foscarnet 40 mg/kg IV every 8 hours (or 60 mg/kg IV every 12 hours) 1, 2, 3

Common Pitfalls to Avoid

Timing errors:

• Treatment must begin within 72 hours of symptom onset for maximal benefit, as peak viral replication occurs in the first 24 hours 3

Route selection mistakes:

• Topical antivirals are ineffective as they cannot reach the site of viral reactivation or impact host immune response 3

Dosing errors in neonates:

• Neonates require the higher 20 mg/kg dose, not the 10 mg/kg dose used in older children with CNS disease 1, 2, 3
• Elimination half-life is significantly prolonged in the first month of life (10-15 hours vs. 2.5 hours in older infants) 6

Inadequate treatment duration:

• Continue therapy until complete lesion healing, not just for a fixed number of days 1, 3