What is the treatment for chickenpox (varicella) in adults?

Treatment of Chickenpox in Adults

Adults with chickenpox should receive oral acyclovir 800 mg four times daily for 5 days, initiated within 24 hours of rash onset for maximum benefit. 1, 2, 3

Antiviral Therapy Recommendations

Standard Treatment for Immunocompetent Adults

• Oral acyclovir 800 mg four times daily for 5 days is the recommended regimen for adults and children over 40 kg with chickenpox 2, 3
• Treatment must be initiated within 24 hours of rash onset to achieve significant clinical benefit, including reduced duration of fever, new lesion formation, and time to complete healing 1, 4
• Clinical trials demonstrate that acyclovir is well-tolerated and effective in reducing disease duration and severity when given early 1
• Five days of therapy is sufficient—extending treatment to 7 days provides no additional benefit 4

Treatment Initiated After 24 Hours

• Acyclovir can still provide some benefit when started 24-48 hours after rash onset, though efficacy is reduced compared to earlier initiation 4
• Adults presenting between 24-48 hours should still receive treatment given the increased severity of chickenpox with age 5
• Treatment initiated beyond 48 hours has minimal documented benefit in immunocompetent patients 4

Immunocompromised Patients

• Immunocompromised adults require intravenous acyclovir 10 mg/kg every 8 hours for 7-10 days, regardless of timing of presentation 2, 3
• IV therapy should be initiated immediately upon diagnosis due to high risk of disseminated infection and mortality 2, 5
• Adequate hydration and monitoring of renal function are essential at these doses 6

Renal Dose Adjustments

• Creatinine clearance 10-25 mL/min: 800 mg every 8 hours 3
• Creatinine clearance 0-10 mL/min: 800 mg every 12 hours 3
• Hemodialysis patients: Administer additional dose after each dialysis session 3

Post-Exposure Prophylaxis

For Susceptible Adults

• Varicella-zoster immune globulin (VZIG) within 96 hours of exposure is first-line prophylaxis for susceptible adults, particularly pregnant women 1, 2, 7
• If VZIG is unavailable or the 96-hour window has passed, acyclovir 800 mg four times daily for 5-7 days starting 7-10 days after exposure is an alternative 2, 7

Pregnancy Considerations

• Pregnant women exposed to varicella should receive VZIG within 96 hours 1, 7
• Acyclovir is FDA Pregnancy Category B with no increased birth defects documented in 596 first-trimester exposures 1, 7
• For pregnant women with active chickenpox complicated by pneumonia or other serious manifestations, intravenous acyclovir should be administered 1
• Routine oral acyclovir prophylaxis during pregnancy is not recommended, but IV therapy is indicated for severe complications 1

Supportive Care

• Symptomatic treatment is appropriate for all patients and includes antipyretics (avoid aspirin due to Reye's syndrome risk), antihistamines for pruritus, and topical calamine 8
• Isolation until all lesions have crusted over is required to prevent transmission 2

Common Pitfalls to Avoid

• Do not delay treatment waiting for laboratory confirmation—chickenpox is a clinical diagnosis and treatment efficacy is time-dependent 4, 5
• Do not confuse chickenpox treatment windows (24 hours) with herpes zoster treatment windows (72 hours)—these are distinct conditions with different therapeutic timeframes 1, 7
• Do not use acyclovir for routine prophylaxis in healthy exposed individuals—vaccination is the preferred method 1
• Do not administer live varicella vaccine to immunocompromised patients due to risk of disseminated infection 2
• Ensure adequate hydration when using high-dose acyclovir to prevent crystalluria and renal complications 6

Secondary Household Cases

• Consider treating secondary household cases with acyclovir, as they tend to develop more severe disease than primary cases 1, 5
• The same dosing regimen applies: 800 mg four times daily for 5 days, initiated within 24 hours of rash onset 1, 3