What is the recommended treatment for cold sores in pediatric patients?

Treatment for Cold Sores in Children

For pediatric patients with cold sores (herpes labialis), oral acyclovir 20 mg/kg per dose (maximum 400 mg/dose) three times daily for 5-10 days is the recommended first-line treatment, continuing until lesions completely heal. 1

Treatment Algorithm by Severity

Mild Cold Sores (Standard Approach)

• Initiate oral acyclovir 20 mg/kg per dose (maximum 400 mg/dose) three times daily for 5-10 days 1, 2
• Treatment should begin at the earliest symptom (tingling, itching, or burning) for maximum efficacy 2
• Continue therapy until lesions completely heal, not just until improvement begins 1, 2
• Monitor for clinical improvement within 48-72 hours 2

Moderate to Severe Disease

• Start with IV acyclovir 5-10 mg/kg per dose three times daily 1, 2
• After lesions begin to regress, transition to oral acyclovir at the same weight-based dosing (20 mg/kg per dose three times daily) 1, 2
• Continue oral therapy until complete healing occurs 1

Age-Specific Considerations

Children ≥12 Years

• Valacyclovir 2 grams twice daily for 1 day (taken 12 hours apart) is FDA-approved 3
• This high-dose, short-duration regimen reduces episode duration by approximately 1 day compared to placebo 4
• Must be able to swallow adult-sized tablets, as no pediatric formulation exists 1

Children <12 Years

• Oral acyclovir remains the only well-studied option 1, 2
• Valacyclovir and famciclovir lack pediatric dosing data and formulations for this age group 1
• Oral suspension can be compounded from 500-mg tablets if needed 3

Neonates with HSV Infections

• Use higher IV acyclovir dosing: 20 mg/kg every 8 hours 2, 5
• Ensure adequate hydration during treatment 5

Treatment Failure

Acyclovir-Resistant Cases

• If no improvement after 5-7 days of appropriate acyclovir therapy, consider IV foscarnet 40 mg/kg per dose three times daily 6, 2, 5
• This is uncommon in immunocompetent children but should be considered in treatment failures 6

Critical Timing Considerations

• Peak viral replication occurs within the first 24 hours after lesion onset 2
• Treatment initiated within the first 3 days of symptom onset provides maximum efficacy 2
• Starting treatment after clinical lesions develop (papule, vesicle, or ulcer) has not been established as effective 3

Common Pitfalls to Avoid

• Do not use topical antivirals alone - they cannot reach the site of viral reactivation or impact the host immune response 2
• Do not stop treatment when symptoms improve - continue until complete healing occurs to prevent recurrence 1, 2
• Do not underdose - ensure weight-based dosing is calculated correctly, with maximum 400 mg/dose for standard oral therapy 1
• Ensure adequate hydration - acyclovir can cause crystalluria and renal toxicity if patients are dehydrated 2, 5

Safety Monitoring

• Monitor for neutropenia - occurs in approximately 21-46% of infants on prolonged therapy, though typically self-limited 2
• Check renal function - dose adjustment required if renal insufficiency develops 2
• Watch for adequate hydration - particularly important to prevent crystalluria 5

Evidence Quality Note

The CDC, American Academy of Pediatrics, and Infectious Diseases Society of America provide AI-level evidence (strong recommendation based on clinical trial data) for oral acyclovir at 20 mg/kg three times daily in children 1, 6, 2. The FDA approval of valacyclovir for children ≥12 years is based on adult efficacy data showing significant reduction in episode duration 3, 4.