Can acyclovir be given to an otherwise healthy 11‑year‑old child for herpes simplex infection, and what is the appropriate dose?

Acyclovir for Herpes Simplex in an 11-Year-Old Child

Yes, acyclovir is safe and appropriate for an 11-year-old child with herpes simplex infection, with the standard oral dose being 20 mg/kg per dose (maximum 400 mg) three times daily for 5-10 days. 1

Standard Dosing Algorithm

For Mild to Moderate HSV Infections (Outpatient)

• Oral acyclovir: 20 mg/kg per dose (maximum 400 mg/dose) three times daily for 5-10 days 2, 1
• Continue therapy until lesions completely heal, not just until symptoms improve 1
• For an 11-year-old weighing approximately 35-40 kg, this translates to 400 mg (the maximum dose) three times daily 1

For Severe HSV Infections (Requiring Hospitalization)

• Start with intravenous acyclovir 5-10 mg/kg per dose three times daily 2, 1
• After lesions begin to regress, transition to oral acyclovir at the same weight-based dosing to complete the treatment course 2, 1

For Disseminated Disease or Encephalitis

• Intravenous acyclovir 10 mg/kg/dose or 500 mg/m²/dose three times daily for 21 days 2, 1

Specific HSV Presentations

Herpetic Gingivostomatitis (Most Common in Children)

• Oral acyclovir 20 mg/kg per dose (maximum 400 mg) three times daily for 5-10 days 1
• Treatment is most effective when initiated within the first 3 days of symptom onset 1
• Expect clinical improvement within 48-72 hours 1

Genital Herpes (If Applicable)

• For children <45 kg: Acyclovir 20 mg/kg per dose (maximum 400 mg) three times daily for 5-14 days 2, 3
• For adolescents ≥45 kg: Acyclovir 400 mg twice daily for 5-14 days 2, 3

Critical Safety Considerations

Monitoring Requirements

• Ensure adequate hydration throughout treatment to prevent acyclovir crystalluria 1, 3
• Monitor for clinical improvement within 48-72 hours of initiating therapy 1
• Neutropenia can occur in 21-46% of children on prolonged therapy, though typically self-limited 1

Dose Adjustments

• Dose adjustment is required if renal insufficiency develops 2, 1
• Acyclovir is primarily excreted by the kidney 2

Treatment Failure Protocol

• If the child fails to respond after 5-7 days of appropriate acyclovir therapy, consider intravenous foscarnet 40 mg/kg per dose three times daily for acyclovir-resistant HSV 2, 1

Common Pitfalls to Avoid

• Do not use topical acyclovir alone as it cannot reach the site of viral reactivation or impact the host immune response 1
• Do not stop treatment early when symptoms improve; continue until complete healing occurs 1
• Do not delay initiation; peak viral replication occurs in the first 24 hours after lesion onset, making early treatment critical 1

Evidence Quality

These recommendations carry an AI rating (strong evidence from randomized controlled trials) from the CDC, National Institutes of Health, and American Academy of Pediatrics 3. The FDA approved oral acyclovir for treatment of varicella in otherwise healthy children in 1992 based on placebo-controlled, double-blind studies demonstrating beneficial clinical effects with no serious adverse events during drug administration 2.