Treatment of Oral HSV in a 5-Year-Old Child
For a healthy 5-year-old with primary oral herpes simplex virus infection (gingivostomatitis), treat with oral acyclovir 20 mg/kg per dose (maximum 400 mg) three times daily for 5-10 days, continuing until all lesions have completely healed. 1
Dosing Algorithm by Severity
Mild to Moderate Gingivostomatitis (Outpatient)
- Initiate oral acyclovir 20 mg/kg per dose (maximum 400 mg/dose) three times daily for 5-10 days 2, 1
- For a 20 kg child, this equals 400 mg (10 mL of suspension) three times daily 1
- For a 15 kg child, this equals 300 mg (7.5 mL of suspension) three times daily 1
- The oral suspension is formulated at 200 mg per 5 mL 2
- Continue therapy until lesions completely heal, not just until improvement begins 1
Moderate to Severe Disease 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 (20 mg/kg/dose three times daily) to complete the treatment course 2, 1
- Monitor clinical improvement within 48-72 hours 1
Critical Timing Considerations
Initiate treatment within the first 3 days of symptom onset for maximum efficacy, as peak viral replication occurs in the first 24 hours after lesion onset 1. The CDC guidelines emphasize that early treatment is essential because the therapeutic window is narrow—waiting beyond 72 hours significantly reduces antiviral effectiveness 1.
Safety Monitoring
- Ensure adequate hydration to prevent crystalluria and renal toxicity 1
- The most common adverse effect is neutropenia, occurring in approximately 21-46% of infants on prolonged therapy, though typically self-limited 1
- Dose adjustment is required if renal insufficiency develops 1
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. This resistance is rare in immunocompetent children but must be considered when lesions persist or worsen despite adequate dosing 3.
Common Pitfalls to Avoid
- Do not stop treatment when symptoms improve; continue until complete healing occurs 1
- Do not use topical antivirals alone as they cannot reach the site of viral reactivation or impact the host immune response 1
- Do not underdose—the 20 mg/kg three times daily regimen is critical for adequate viral suppression 2, 1
- Primary labial herpes in otherwise healthy children may not require antivirals in very mild cases, but moderate symptomatic gingivostomatitis warrants treatment 4
Red Flags Requiring Immediate IV Therapy
- Fever, irritability, or systemic symptoms in conjunction with vesicular lesions require immediate evaluation for disseminated HSV 5
- Any concern for HSV encephalitis requires immediate IV acyclovir 10 mg/kg per dose three times daily for 21 days 2, 5
- Inability to maintain oral hydration due to severe oral pain warrants hospitalization and IV acyclovir 5