Recommended Medication for Chickenpox
Oral acyclovir is the primary treatment for chickenpox, dosed at 20 mg/kg (maximum 800 mg) four times daily for 5 days in children, or 800 mg four times daily for 5 days in adults and children >40 kg, but must be initiated within 24 hours of rash onset for maximum efficacy. 1, 2
Treatment by Patient Population
Immunocompetent Patients
Children (<40 kg):
- Oral acyclovir 20 mg/kg per dose (maximum 800 mg) four times daily for 5 days 1, 3, 2
- Treatment must begin within 24 hours of rash onset for optimal benefit 1, 4
- Five days of therapy is sufficient; 7-day courses provide no additional benefit 1, 4
Adolescents ≥12 years and Children >40 kg:
- Oral acyclovir 800 mg four times daily for 5 days 1, 3, 2
- This population should be prioritized for treatment due to increased disease severity with age 1, 5
Adults:
- Oral acyclovir 800 mg four times daily for 5-7 days 1, 2
- Adults experience more severe disease and should receive treatment regardless of timing concerns 1, 5
Immunocompromised Patients
Intravenous acyclovir is mandatory for all immunocompromised patients:
- 10 mg/kg IV every 8 hours for 7-10 days 6, 1, 3
- Alternative dosing: 500 mg/m²/dose IV every 8 hours in children >1 year 1
- Treatment should be initiated regardless of timing from rash onset due to high risk of disseminated infection 7, 5
- Continue therapy until no new lesions appear for 48 hours 1
- Consider discontinuing immunomodulator therapy if clinically feasible 1
High-Risk Groups Requiring Treatment
The following immunocompetent patients should receive acyclovir therapy:
- Patients with chronic cutaneous or pulmonary disorders 1, 3
- Patients receiving long-term salicylate therapy 1, 3
- Patients on corticosteroid therapy (short, intermittent, or aerosolized) 1, 3
- Secondary household contacts of infected children 1
- Pregnant women (though routine use not generally recommended; FDA Pregnancy Category B) 1, 7
Post-Exposure Prophylaxis
Varicella Zoster Immune Globulin (VZIG):
- Administer as soon as possible, up to 96 hours after exposure (some sources extend to 10 days) 6, 1, 3
- Indicated for:
If VZIG is unavailable or >96 hours post-exposure:
- Oral acyclovir 10 mg/kg four times daily for 7 days, starting 7-10 days after exposure 6, 1, 3
- This applies to susceptible immunocompromised patients only 1, 7
Critical Timing Considerations
The evidence demonstrates a clear efficacy gradient based on timing:
- Maximum clinical benefit occurs when treatment begins within 24 hours of rash onset 1, 4
- Treatment initiated on day 2 of rash shows some benefit, particularly for time to maximum lesion formation and healing in adolescents 4
- Treatment initiated on day 3 shows minimal to no benefit in immunocompetent patients 4
- Exception: Immunocompromised patients should receive treatment regardless of timing due to risk of disseminated infection 7, 5
Infection Control Measures
- Isolate patients until all lesions have crusted over 1, 3
- Healthcare workers without immunity exposed to VZV should be furloughed from days 10-21 after exposure 1, 3
Vaccination Considerations
- Live varicella vaccination is contraindicated in immunocompromised patients due to risk of disseminated infection 1, 3
- Susceptible household contacts of immunocompromised patients should be vaccinated to prevent transmission 1, 3
- Delay varicella vaccination 5 months after VZIG administration 1, 3
Important Clinical Caveats
- Acyclovir does not eradicate latent virus or affect subsequent risk of herpes zoster 1
- Antibody titers after infection in children receiving acyclovir do not differ substantially from untreated patients 1
- Do not confuse chickenpox treatment (24-hour window) with herpes zoster treatment (72-hour window) 7
- Acyclovir prophylaxis is not indicated for healthy individuals after exposure 1