Treatment of Cold Sores in Toddlers
For toddlers aged 2 years and older with cold sores (herpes labialis), treat with oral acyclovir 20 mg/kg per dose (maximum 400 mg/dose) three times daily for 5-10 days, initiated at the earliest symptom such as tingling, itching, or burning. 1
Treatment Algorithm by Age and Severity
For Children ≥12 Years
- High-dose, short-duration regimen: Valacyclovir 2 grams twice daily for 1 day (12 hours apart) is FDA-approved and highly effective 2
- This regimen must be initiated at the earliest symptom (tingling, itching, burning) before visible lesions develop 2
- Critical timing: Treatment initiated after papule, vesicle, or ulcer formation has not been established as effective 2
For Children 2 to <12 Years
- Oral acyclovir 20 mg/kg per dose (maximum 400 mg/dose) three times daily for 5-10 days 1
- The CDC provides strong evidence (AI rating) supporting this approach 1
- Continue therapy until lesions completely heal 3, 1
For Children <2 Years
- Acyclovir is not FDA-approved for cold sores in this age group 2
- However, CDC guidelines support oral acyclovir 20 mg/kg three times daily for mild HSV infections in infants, with close monitoring 4
Escalation for Severe Disease
If mild oral therapy fails or disease is moderate-to-severe:
- Switch to intravenous acyclovir 5-10 mg/kg per dose three times daily 3, 1
- After lesions begin to regress, transition back to oral acyclovir to complete the treatment course 3, 1
- Monitor for clinical improvement within 48-72 hours 4, 1
Special Considerations for Neonates
For neonates with HSV infection (not typical cold sores):
- Use high-dose IV acyclovir 20 mg/kg every 8 hours 4, 1
- Duration: 14 days for skin/eye/mouth disease, 21 days for CNS disease 3
- For CNS disease, repeat CSF HSV DNA PCR at days 19-21 and do not discontinue acyclovir until negative 3, 1
Monitoring and Safety
Watch for these adverse events during treatment:
- Neutropenia: Most common laboratory adverse event, occurring in 25% of infants on high-dose therapy, though usually self-limited 3, 5
- Renal toxicity: Ensure adequate hydration throughout treatment; elevated creatinine is rare (2% of infants) 4, 1, 5
- Dose adjustment required for renal insufficiency based on creatinine clearance 3
Critical Pitfalls to Avoid
- Do not use topical antivirals: They cannot reach the site of viral reactivation or impact host immune response 1
- Timing is everything: Peak viral replication occurs in the first 24 hours after lesion onset, making early treatment imperative 1
- Do not delay treatment for laboratory confirmation in immunocompetent children with typical presentations 1
- Valacyclovir is not appropriate for children <12 years: No pediatric formulation exists and dosing data are limited 3
Acyclovir-Resistant Cases
For treatment failures or confirmed resistance:
- Switch to foscarnet 40 mg/kg per dose IV three times daily 3, 4, 1
- This is recommended by the Infectious Diseases Society of America for acyclovir-resistant HSV 1
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