What medications are recommended for an adult with chickenpox (varicella)?

Treatment of Chickenpox in Adults

Adults with chickenpox should receive oral acyclovir 800 mg five times daily for 5-7 days, initiated within 24 hours of rash onset for maximum benefit. 1, 2

Indications for Antiviral Treatment

All adults with chickenpox warrant antiviral therapy, as they are at substantially higher risk for severe complications compared to children. 1, 3 The key complications include:

• Pneumonitis (most common serious complication in adults) 4, 3
• Hepatitis and visceral dissemination 4, 3
• Hemorrhagic varicella 4
• Secondary bacterial skin infections 4, 5
• Central nervous system complications including encephalitis 4

Adults over 12 years of age are specifically identified as a high-risk group requiring antiviral therapy. 1

Standard Dosing Regimen

Oral acyclovir: 800 mg orally 4-5 times daily for 5-7 days 1, 2

• Treatment must be initiated within 24 hours of rash onset for optimal efficacy 1, 6
• Continue treatment for the full 5-7 day course even if symptoms improve 2
• The 800 mg dose is critical—lower doses (such as 400 mg) are inadequate for varicella-zoster virus infection 2

When to Escalate to Intravenous Therapy

Switch to IV acyclovir 10 mg/kg every 8 hours if: 1, 7

• Severe disease with extensive cutaneous involvement 7, 3
• Immunocompromised patients (on corticosteroids, chemotherapy, biologics, or other immunosuppressants) 1, 7
• Visceral complications (pneumonitis, hepatitis, encephalitis) 4, 7
• Inability to tolerate oral medications 3
• Hemorrhagic varicella 4

Continue IV therapy for 7-10 days and at least until all lesions have crusted over. 1, 7

Special Populations Requiring Aggressive Management

Immunocompromised patients: 1

• Immediately discontinue immunomodulator therapy during active chickenpox infection 1
• Do not commence or continue immunosuppressive therapy during active infection 1
• Start IV acyclovir 10 mg/kg every 8 hours immediately 1
• Immunomodulator therapy can only be reintroduced after all vesicles have crusted over and fever has resolved 1

Pregnant women: 6

• Oral acyclovir 800 mg five times daily for mild disease 6
• IV acyclovir for serious complications like pneumonia 6

Patients on chronic salicylate or corticosteroid therapy: 1

• Require antiviral therapy due to increased risk of Reye syndrome (salicylates) and severe disease (corticosteroids) 1

Post-Exposure Prophylaxis

For susceptible adults exposed to active chickenpox: 1

First-line: Varicella-Zoster Immune Globulin (VZIG) within 96 hours of exposure 8, 1

• Particularly critical for immunocompromised patients and pregnant women 8
• Cost is approximately $400 for adult dose 8

Alternative if VZIG unavailable: 8, 1

• Acyclovir 800 mg orally four times daily for 7 days, starting 7-10 days after exposure 8, 1

Renal Dose Adjustments

For patients with renal impairment, acyclovir dosing must be adjusted: 2

• CrCl >25 mL/min: 800 mg every 4 hours (5 times daily) 2
• CrCl 10-25 mL/min: 800 mg every 8 hours 2
• CrCl 0-10 mL/min: 800 mg every 12 hours 2
• Hemodialysis patients: Administer additional dose after each dialysis session 2

Maintain adequate hydration during therapy to prevent acyclovir crystalluria. 7

Adjunctive Therapy

Symptomatic management: 5, 3

• Antihistamines for pruritus 5
• Acetaminophen for fever (avoid aspirin due to Reye syndrome risk) 3

Antibiotics only if secondary bacterial infection develops: 4, 5

• Co-amoxiclav or ceftriaxone for bacterial superinfection 5
• Do not use prophylactic antibiotics 5

Corticosteroids are NOT recommended and may worsen outcomes by increasing viral replication. 5

Infection Control

• Isolate patients until all lesions have crusted over 1
• Chickenpox remains contagious to susceptible individuals throughout the vesicular stage 6
• Healthcare workers exposed without immunity should be furloughed days 10-21 post-exposure 1

Critical Pitfalls to Avoid

• Never delay treatment waiting for laboratory confirmation—chickenpox is a clinical diagnosis and treatment efficacy drops dramatically after 24 hours 1, 6
• Never use inadequate dosing (e.g., 400 mg doses appropriate for herpes simplex are insufficient for varicella) 2
• Never continue immunosuppressive therapy during active chickenpox in severe cases—this substantially increases mortality risk 1
• Never assume immunity based on age alone—verify history or serology, as 30-35% of adults remain susceptible 1
• Never use topical acyclovir—it is substantially less effective than systemic therapy 7