What are the recommended antiviral and supportive treatments, including dosing, for varicella (chickenpox) in otherwise healthy children, adults, and high‑risk patients?

Chickenpox Medications for Adults and Children

Oral Acyclovir for Otherwise Healthy Children

Oral acyclovir is NOT routinely recommended for uncomplicated chickenpox in otherwise healthy children under 12 years because the benefit is marginal—it shortens fever by only 1 day and reduces symptom severity by 15–30%, without preventing complications, transmission, or school absence. 1, 2, 3

• Treatment must begin within 24 hours of rash onset to have any effect; beyond this window, acyclovir provides no benefit. 1, 2, 3
• The cost-benefit ratio does not support routine use in healthy young children. 3

High-Risk Otherwise Healthy Patients Who Should Receive Oral Acyclovir

Consider oral acyclovir for the following groups if treatment can start within 24 hours of rash onset:

• Adolescents and adults ≥13 years, who face higher risk of moderate-to-severe disease and complications. 1, 2, 3
• Children with chronic cutaneous disorders (e.g., eczema) or chronic pulmonary disease (e.g., cystic fibrosis), where varicella may exacerbate the underlying condition or increase risk of secondary bacterial sepsis. 1, 2, 4, 3
• Children on long-term salicylate therapy (e.g., for Kawasaki disease or juvenile arthritis), though acyclovir has not been proven to reduce Reye syndrome risk. 1, 3
• Secondary household cases, who often develop more severe disease due to higher viral inoculum from prolonged exposure. 2

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Dosing Regimens for Oral Acyclovir

Children ≥2 Years and <40 kg

• 20 mg/kg per dose orally four times daily (maximum 800 mg per dose) for 5 days. 1, 2, 5

Children >40 kg and Adults

• 800 mg orally four times daily for 5 days. 1, 2, 5

Renal Impairment Adjustments

• CrCl >10 mL/min: 800 mg every 4 hours (5 times daily). 2, 5
• CrCl 10–25 mL/min: 800 mg every 8 hours. 2, 5
• CrCl <10 mL/min: 800 mg every 12 hours. 2, 5
• Hemodialysis patients: Administer an additional dose after each dialysis session. 5

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Intravenous Acyclovir for Immunocompromised Patients

All immunocompromised patients with chickenpox must receive intravenous acyclovir regardless of timing from rash onset, as it reduces varicella-associated morbidity and mortality, halts viral dissemination, and prevents visceral complications. 1, 2, 6, 7

High-Risk Immunocompromised Groups Requiring IV Acyclovir

• Children with leukemia, lymphoma, or other hematologic malignancies. 2
• Patients receiving chemotherapy, long-term immunosuppressive therapy, or organ transplant recipients. 2
• HIV-infected individuals with CD4 <200 cells/µL. 8, 2
• Patients with primary immunodeficiency disorders. 2

IV Acyclovir Dosing

• 1500 mg/m² per day IV divided into three doses (or 10 mg/kg IV every 8 hours). 1
• Continue treatment until all lesions have scabbed over. 1
• Maintain adequate hydration and monitor renal function and mental status at these doses. 6

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Pregnancy Considerations

Pregnant women with mild chickenpox may receive oral acyclovir 800 mg five times daily for 5 days if treatment begins within 24 hours; for severe complications such as pneumonia, switch to IV acyclovir. 1, 2

• Acyclovir is FDA Pregnancy Category B—animal studies show no teratogenic effect, though human data are limited. 2
• VZV-susceptible pregnant women exposed to chickenpox should receive varicella-zoster immune globulin (VZIG) within 96 hours of exposure. 8, 2

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Newborns and Premature Infants

High-risk newborns require prophylaxis with VZIG within 96 hours of exposure:

• Premature infants <28 weeks gestation or <1,000 g exposed to varicella. 2
• Newborns whose mothers develop varicella from 5 days before to 2 days after delivery. 2

If active chickenpox develops despite prophylaxis, treat with IV acyclovir. 2, 4

• Newborns during the first 2 weeks of life with varicella should receive IV acyclovir due to risk of severe disseminated disease. 4

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Valacyclovir as an Alternative

Valacyclovir 20 mg/kg orally three times daily for 5 days (maximum 1 gram per dose) is FDA-approved for chickenpox in children aged 2 to <18 years. 9

• Valacyclovir is a prodrug of acyclovir with better oral bioavailability, allowing three-times-daily dosing instead of four. 9
• It is not approved for children <2 years because safety and efficacy data are lacking in this age group. 9
• For adults, valacyclovir 1 gram three times daily for 5 days is an alternative to oral acyclovir 800 mg five times daily. 9

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Post-Exposure Prophylaxis

VZIG (Varicella-Zoster Immune Globulin)

Administer VZIG within 96 hours of exposure to:

• VZV-susceptible pregnant women. 8, 2
• Immunocompromised patients without evidence of immunity. 8, 2
• Premature infants <28 weeks or <1,000 g. 2
• Newborns of mothers with peripartum varicella. 2

Maximum benefit occurs when VZIG is given as soon as possible, but it remains effective up to 96 hours post-exposure. 2

Varicella Vaccine for Post-Exposure Prophylaxis

• Varicella vaccine may be given 3–5 days after exposure to modify disease if infection has not yet occurred. 2
• Contraindicated in immunocompromised patients and pregnant women. 2

Oral Acyclovir as Alternative PEP

• When VZIG is unavailable or >96 hours have passed, consider oral acyclovir starting 7–10 days after exposure for 7 days. 2

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Key Limitations and Caveats

• Acyclovir does NOT reduce household transmission of varicella. 1, 2
• Acyclovir does NOT shorten duration of school absence; patients must remain isolated until all lesions are crusted. 1, 2
• Acyclovir does NOT clearly prevent complications in otherwise healthy children (studies were underpowered for this outcome). 2, 3
• Acyclovir treatment does NOT increase future herpes zoster risk—antibody titers normalize by 1 year post-infection, and viral latency establishment is unaffected. 10
• Famciclovir is NOT FDA-approved for chickenpox and should not be used off-label; acyclovir is the established agent with documented safety and efficacy. 1

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Supportive Care for All Patients

• Antipyretics: Acetaminophen is preferred; avoid aspirin and NSAIDs in children due to Reye syndrome risk and potential increased risk of invasive group A streptococcal infection. 3
• Antihistamines (e.g., diphenhydramine) for pruritus. 11
• Topical calamine lotion or colloidal oatmeal baths to soothe skin. 11
• Antibiotics (e.g., co-amoxiclav or ceftriaxone) only if secondary bacterial skin infection develops. 11
• Maintain hydration and monitor for complications (pneumonia, encephalitis, cerebellar ataxia, secondary bacterial infection). 11, 7