When to Give Acyclovir for Varicella in Children
Oral acyclovir is NOT routinely recommended for healthy children under 12 years with uncomplicated chickenpox, but should be initiated within 24 hours of rash onset for high-risk children including those ≥12 years, those with chronic cutaneous or pulmonary disorders, and those on long-term salicylate therapy. 1, 2
Indications for Oral Acyclovir in Children
High-Risk Groups Requiring Treatment
Children ≥12 years of age should receive oral acyclovir 800 mg four times daily for 5 days when treatment can be started within 24 hours of rash onset 2, 3
Children with chronic cutaneous disorders (e.g., eczema, atopic dermatitis) should be considered for treatment due to risk of severe disease and secondary bacterial infection 1, 2, 4
Children with chronic pulmonary disease warrant acyclovir therapy to prevent exacerbation of underlying respiratory conditions 1, 2
Children receiving long-term salicylate therapy should receive acyclovir, though this does not eliminate Reye syndrome risk 1, 5
Immunocompromised Children
HIV-infected or immunocompromised children require 20 mg/kg orally (maximum 800 mg/dose) 4 times daily for 7-10 days or until no new lesions appear for 48 hours 1
Severely immunosuppressed children should receive intravenous acyclovir 10 mg/kg every 8 hours for 7-10 days, followed by oral therapy 1, 4
Neonates and preterm infants in the first 2 weeks of life require intravenous acyclovir due to high risk of disseminated disease 4
Dosing Regimen for Children
Weight-Based Oral Dosing
Standard pediatric dose: 20 mg/kg per dose (maximum 800 mg) orally 4 times daily for 5 days 1, 3
For a 24 kg child: approximately 480 mg per dose, four times daily, totaling 1,920 mg per day 1
Children over 40 kg: receive the adult dose of 800 mg four times daily for 5 days 3
Critical Timing Requirement
Treatment must begin within 24 hours of rash onset to achieve meaningful clinical benefit; initiation after this window provides markedly diminished efficacy 1, 2, 5, 6, 7
Delay beyond 24 hours results in loss of therapeutic effect in otherwise healthy individuals 5, 6
Duration Adjustments
Immunocompromised children: extend to 7-10 days or continue until no new lesions for 48 hours 1
When NOT to Give Acyclovir
Routine Use Not Recommended
Healthy children under 12 years with uncomplicated varicella should NOT receive routine acyclovir because the marginal benefit (1-day reduction in fever, 15-30% reduction in symptoms) does not justify routine use 1, 5
Acyclovir does not reduce acute complications, pruritus, spread of infection, or duration of school absence in healthy children 5
The drug does not prevent transmission or reduce isolation requirements—patients remain contagious until all lesions crust 2
Common Pitfalls to Avoid
Dosing Errors
Never underdose: Do not apply adult fixed-dose regimens (800 mg) to children under 40 kg; always calculate 20 mg/kg per dose 1
Never exceed maximum single dose: Do not give more than 800 mg in a single oral administration regardless of weight 1, 3
Route Selection Errors
Do not use oral acyclovir for severely immunocompromised children or those under 2 years with serious disease—intravenous therapy is mandatory 1, 4
Do not delay IV therapy in neonates, children with altered cell-mediated immunity, or those with severe/disseminated disease 4
Timing Errors
Do not initiate treatment after 24 hours in otherwise healthy children—the therapeutic window has closed 1, 2, 5, 6
Do not stop treatment prematurely in immunocompromised children—continue until no new lesions for 48 hours, even if this exceeds 7-10 days 1