What is the recommended treatment for adult chicken pox (varicella)?

Treatment of Adult Chickenpox (Varicella)

Oral acyclovir 800 mg four times daily for 5 days should be initiated within 24 hours of rash onset for all adults with chickenpox to reduce disease severity, duration of fever, and time to healing. 1, 2

Timing is Critical for Efficacy

• Treatment must begin within 24 hours of rash appearance to achieve meaningful clinical benefit; initiating therapy beyond this window results in loss of therapeutic effect 1, 3, 4
• Starting acyclovir on day 1 of rash reduces time to complete crusting from 7.4 to 5.6 days and cuts fever duration by half a day 4
• Therapy initiated within 24 hours reduces maximum lesion formation time, accelerates progression to crusted/healed stages, and decreases constitutional symptoms to 3-4 days versus >4 days with placebo 3, 5
• Five days of therapy is sufficient—a 7-day course provides no additional benefit 3

Standard Dosing Regimen

• Adults and children >40 kg: 800 mg orally four times daily for 5 days 2
• Children 2 years and older: 20 mg/kg per dose (maximum 800 mg) four times daily for 5 days 2
• Dosing should be adjusted for renal impairment: creatinine clearance 10-25 mL/min requires 800 mg every 8 hours; <10 mL/min requires 800 mg every 12 hours 2

Special Populations Requiring Treatment

Immunocompromised Patients

• Intravenous acyclovir is indicated for all immunocompromised patients with varicella regardless of timing, as chickenpox is potentially fatal in this population 1, 6
• Treatment should be initiated immediately upon recognition due to high risk of disseminated infection and visceral complications 7, 6

Pregnant Women

• Acyclovir is FDA Pregnancy Category B with no increased birth defects documented in 596 first-trimester exposures 1, 7
• Intravenous acyclovir should be considered for pregnant women with serious viral-mediated complications such as pneumonia 1
• For uncomplicated varicella in pregnancy, the decision requires weighing individual risk factors, though oral acyclovir is not routinely recommended by AAP for uncomplicated cases 1

Adults with Complicated Varicella

• Adults with symptomatic varicella pneumonia or other visceral complications require intravenous acyclovir 4
• Secondary and tertiary household cases tend to be more severe and should receive treatment 6

Post-Exposure Prophylaxis

For Susceptible Adults After Exposure

• Varicella-zoster immune globulin (VZIG) within 96 hours of exposure is first-line prophylaxis for susceptible adults, particularly pregnant women and immunocompromised individuals 1, 7
• If VZIG is unavailable or >96 hours post-exposure, acyclovir 20 mg/kg (maximum 800 mg) four times daily for 5-7 days, initiated 7-10 days after exposure, is an alternative 7
• Vaccination is the preferred method for post-exposure prophylaxis in healthy adults without contraindications; acyclovir is not indicated for prophylactic use in otherwise healthy individuals 1

Healthcare Personnel Management

• Unvaccinated healthcare workers exposed to varicella should receive post-exposure vaccination within 3-5 days of exposure 1
• Healthcare workers who develop symptoms should be furloughed from days 10-21 after exposure 1

Clinical Outcomes and Benefits

• Acyclovir treatment reduces mean lesion count (294 vs 347 with placebo), with fewer patients developing >500 lesions (21% vs 38%) 5
• Over 95% of acyclovir recipients stop forming new lesions by day 3, compared to 20% of placebo recipients still forming lesions on day 6 or later 5
• Treatment accelerates healing, reduces itching, and results in fewer residual lesions at 28 days 5
• No evidence suggests acyclovir reduces rare serious complications such as bacterial superinfection or cerebellar ataxia in otherwise healthy individuals 5

Important Caveats and Pitfalls

• Do not confuse varicella treatment (24-hour window) with herpes zoster treatment (72-hour window) for optimal efficacy 7
• Acyclovir does not reduce viral shedding to latent ganglia, so it does not prevent future herpes zoster risk 3
• Viral resistance has not been documented with standard 5-day courses; viruses shed during therapy retain normal thymidine kinase function and acyclovir susceptibility 3
• Birth before 1980 is NOT considered evidence of immunity for healthcare personnel due to nosocomial transmission risk to high-risk patients 1
• Most adults (88-91%) with negative or unknown varicella history are actually immune; serologic screening before treatment decisions may be cost-effective in healthcare settings 1