What are the treatment options for varicella (chickenpox)?

Treatment of Varicella (Chickenpox)

For immunocompetent adults and adolescents with varicella, oral acyclovir 800 mg five times daily for 5 days should be initiated within 24 hours of rash onset to reduce disease severity, with intravenous acyclovir 10 mg/kg every 8 hours reserved for complicated cases such as varicella pneumonia or immunocompromised patients. 1, 2

Treatment Approach by Patient Population

Immunocompetent Adults and Adolescents

• Oral acyclovir 800 mg four times daily for 5 days is the FDA-approved regimen for adults and children over 40 kg with chickenpox 1
• Treatment must be initiated within 24 hours of rash onset for optimal efficacy—therapy started after this window shows minimal benefit 1, 2, 3
• When initiated early, oral acyclovir reduces time to complete crusting from 7.4 to 5.6 days and decreases fever duration by half a day 3
• Adults and adolescents are at higher risk for severe disease and complications compared to children, making antiviral treatment particularly important in this population 4, 3

Immunocompromised Patients

• Intravenous acyclovir is mandatory for immunocompromised patients with varicella regardless of timing, as they face high risk of disseminated infection and visceral complications 2, 5
• IV acyclovir causes more rapid resolution of illness and fewer complications in this population 5
• Immunocompromised patients should receive antiviral therapy even if treatment is initiated beyond 24 hours due to their elevated risk profile 2

Children (2 Years and Older)

• For otherwise healthy children, oral acyclovir 20 mg/kg per dose (maximum 800 mg) four times daily for 5 days is FDA-approved but not routinely recommended 1
• Treatment should be initiated within 24 hours of rash onset if used 1
• Chickenpox in healthy children is usually self-limited and mild, making routine antiviral treatment unnecessary 1
• Consider treatment for children who are sibling contacts or have other medical conditions that increase risk 4

Complicated Varicella

• Intravenous acyclovir 10 mg/kg every 8 hours for 7-10 days is indicated for varicella pneumonia, CNS complications, or other severe manifestations 5, 2
• Adults with symptomatic varicella pneumonia require IV acyclovir regardless of timing 3
• Adequate hydration and monitoring of renal function are essential during IV therapy 1, 5

Post-Exposure Prophylaxis

Varicella-Zoster Immune Globulin (VZIG)

• VZIG should be administered within 96 hours of exposure to susceptible high-risk individuals including pregnant women, immunocompromised patients, and premature infants <28 weeks gestation or <1,000 g 6, 2
• For pregnant women, VZIG prevents maternal complications rather than fetal infection—it does not prevent congenital varicella syndrome 6
• Neonates born to mothers with varicella from 5 days before to 2 days after delivery should receive VZIG regardless of whether the mother received it 6

Acyclovir Prophylaxis

• If VZIG is unavailable or more than 96 hours have passed since exposure, acyclovir 20 mg/kg (maximum 800 mg) four times daily for 5-7 days starting 7-10 days after exposure is an alternative 2
• This approach is less well-established than VZIG but provides an option when immune globulin is not accessible 2

Special Populations

Pregnancy

• Acyclovir is FDA Pregnancy Category B with no documented increase in birth defects based on 749 first-trimester exposures 2, 1
• Pregnant women are at higher risk for severe varicella and complications, warranting consideration of treatment 6
• VZIG is strongly preferred for post-exposure prophylaxis in pregnant women without immunity 2

Neonates

• Premature infants born at <28 weeks gestation or weighing <1,000 g should receive VZIG after exposure regardless of maternal immunity status 6
• Healthy full-term infants exposed postnatally do not require VZIG even if mothers lack varicella history 6
• Intravenous acyclovir is effective for varicella in neonates when treatment is indicated 4

Critical Treatment Caveats

• Do not confuse varicella treatment (24-hour window) with herpes zoster treatment (72-hour window)—these are distinct conditions with different treatment timelines 2
• Topical acyclovir is substantially less effective than systemic therapy and should not be used 7
• Varicella vaccine is contraindicated during active infection but should be considered after recovery for those who remain susceptible 6
• Maintain adequate hydration during oral or IV acyclovir therapy to prevent renal complications 1, 5
• Monitor renal function and adjust dosing in patients with renal impairment according to creatinine clearance 1
• Patients receiving VZIG should be observed for 28 days after exposure as it may prolong the incubation period 6