Acyclovir Treatment for Varicella (Chickenpox)
Primary Recommendation
Oral acyclovir is NOT routinely recommended for otherwise healthy children with uncomplicated varicella, but SHOULD be initiated within 24 hours of rash onset for high-risk populations including persons ≥13 years, immunocompromised patients, pregnant women with complications, and children with chronic cutaneous or pulmonary disorders. 1, 2, 3
Treatment Algorithm by Patient Population
Healthy Children (<13 years)
- Supportive care only for otherwise healthy children without risk factors 2, 3
- Oral acyclovir provides only marginal benefit (1-day reduction in fever, 15-30% reduction in symptom severity) and does not reduce acute complications, pruritus, or school absence 3, 4
- Exception: Consider oral acyclovir 20 mg/kg four times daily (maximum 800 mg/dose) for 5 days if the child has chronic cutaneous disorders (e.g., eczema), chronic pulmonary disease, or receives long-term salicylate therapy—but ONLY if started within 24 hours of rash onset 1, 5, 6, 3
Adolescents and Adults (≥13 years)
- Oral acyclovir 800 mg four times daily for 5 days should be initiated within 24 hours of rash onset 2, 6, 3
- This population faces significantly higher complication rates (case-fatality rate 21.3 per 100,000 vs 0.8 per 100,000 in young children) 2
- Treatment beyond 24 hours results in loss of therapeutic effect 2, 7
Immunocompromised Patients
- Intravenous acyclovir 10 mg/kg every 8 hours for 7-10 days should be initiated immediately upon diagnosis, ideally within 24 hours of rash onset 2, 6, 8
- This includes HIV-infected patients, transplant recipients, cancer patients on chemotherapy, and those receiving high-dose corticosteroids 2, 8
- Treatment should continue until all lesions have crusted over, not just for an arbitrary 7-day duration 9
- IV acyclovir substantially reduces mortality and risk of severe disease in this population 8, 10
- Antiviral therapy should be given regardless of timing in immunocompromised patients due to high risk of disseminated infection 9
Pregnant Women
- Intravenous acyclovir should be considered for serious viral-mediated complications such as pneumonia 1, 2
- Acyclovir is FDA Category B in pregnancy with reassuring safety data from 596 first-trimester exposures showing no increased birth defect rates 1, 2
- Oral acyclovir may be considered for pregnant women at increased risk for moderate-to-severe disease if started within 24 hours 2
Neonates
- Intravenous acyclovir is recommended for newborns during the first 2 weeks of life and preterm infants in the neonatal nursery 8
- Newborns whose mothers developed varicella from 5 days before to 2 days after delivery face high mortality risk and require immediate treatment if varicella develops 2
Dosing Specifications
Oral Acyclovir for Varicella 6
- Children (2 years and older): 20 mg/kg per dose four times daily (80 mg/kg/day) for 5 days
- Children over 40 kg and adults: 800 mg four times daily for 5 days
- Critical timing: Must be initiated within 24 hours of rash onset for efficacy 5, 2, 7
Renal Dose Adjustments 6
- CrCl >25 mL/min: 800 mg every 4 hours, 5 times daily
- CrCl 10-25 mL/min: 800 mg every 8 hours
- CrCl 0-10 mL/min: 800 mg every 12 hours
- Hemodialysis: Administer additional dose after each dialysis session 6
Post-Exposure Prophylaxis
Immunocompetent Individuals
- Varicella vaccine within 3 days (up to 5 days) of exposure is >90% effective at preventing disease and is the method of choice 2
- Acyclovir is NOT indicated for prophylactic use in otherwise healthy individuals after exposure 1, 2
High-Risk Individuals
- Varicella-zoster immune globulin (VariZIG) within 96 hours (up to 10 days) for immunocompromised patients, pregnant women without immunity, and high-risk newborns 2
- Dosing: 125 IU/10 kg body weight IM, maximum 625 IU 2
- If varicella develops despite VariZIG, initiate antiviral therapy immediately 2
Critical Pitfalls to Avoid
- Do not delay treatment beyond 24 hours in populations where acyclovir is indicated—efficacy is lost after this window 5, 2, 7
- Do not use acyclovir prophylactically in healthy individuals; vaccination is superior 1, 2
- Do not withhold IV acyclovir from immunocompromised patients based on timing—treat regardless of when rash appeared 9
- Do not use oral acyclovir in children <2 years requiring treatment; use IV formulation 8
- Do not assume acyclovir prevents future herpes zoster—it does not alter viral latency establishment or immune memory formation 5