Treatment of Chicken Pox (Varicella)
For chicken pox (varicella), oral acyclovir is the recommended treatment, particularly for patients at higher risk for moderate to severe disease. 1, 2
Treatment Recommendations by Patient Population
Children
- For children 2 years and older: Oral acyclovir 20 mg/kg per dose 4 times daily (80 mg/kg/day) for 5 days 3
- Children over 40 kg should receive the adult dose 3
- Treatment should be initiated within 24 hours of rash onset for maximum effectiveness 1, 4
Adults and Children over 40 kg
- Oral acyclovir 800 mg 4 times daily for 5 days 3
- Five days of therapy is sufficient as studies show a 7-day course provides no additional benefit 4
High-Risk Populations
- Acyclovir should be considered for patients at increased risk for moderate to severe varicella, including: 1
- Persons aged >12 years
- Persons with chronic cutaneous or pulmonary disorders
- Persons receiving long-term salicylate therapy
- Persons receiving short, intermittent, or aerosolized courses of corticosteroids
Immunocompromised Patients
- Intravenous acyclovir is indicated for varicella-zoster infections in immunocompromised patients 3, 5
- For HIV-infected children in CDC class 1 with CD4 T-lymphocyte percentage ≥15%, varicella vaccine should be considered rather than treatment after exposure 1
Pregnant Women
- For pregnant women with serious varicella complications, intravenous acyclovir should be considered 1, 2
- Acyclovir is classified as a Category B drug in pregnancy 1, 3
- A registry of infants whose mothers received systemic acyclovir during the first trimester showed no increased rate of birth defects 1, 2
Clinical Considerations
Timing of Treatment
- Treatment should be initiated at the earliest sign or symptom of chickenpox 3
- Maximum effectiveness is achieved when acyclovir is administered within 24 hours of rash onset 1, 4
- There is no information about the efficacy of therapy initiated more than 24 hours after onset of signs and symptoms 3
- However, some benefit has been observed when treatment is started within 48 hours of rash onset 4
Benefits of Treatment
- Acyclovir reduces the number of lesions and shortens the duration of new lesion formation 6
- Treatment decreases fever duration and severity of cutaneous and systemic symptoms 1
- Patients begin to feel better sooner with fewer systemic signs and symptoms (fever, fatigue, loss of appetite) 6
Limitations of Treatment
- Acyclovir does not decrease transmission of varicella 1
- It does not reduce the duration of absence from school 1
Post-Exposure Prophylaxis
For Immunocompromised Individuals
- Varicella-Zoster Immune Globulin (VZIG) is recommended for susceptible immunocompromised patients within 96 hours of exposure 1, 2
For Healthy Individuals
- Vaccination is the method of choice for post-exposure prophylaxis in healthy individuals without evidence of immunity 1
Special Considerations
Renal Impairment
- Dose adjustment is necessary for patients with renal impairment 3
- For creatinine clearance 10-25 mL/min/1.73m², 800 mg acyclovir should be given every 8 hours 3
- For creatinine clearance <10 mL/min/1.73m², 800 mg acyclovir should be given every 12 hours 3
Hydration
- Adequate hydration should be maintained during acyclovir treatment 3
Viral Resistance
- Studies have shown that viruses shed during therapy remained susceptible to acyclovir and retained normal thymidine kinase function 4
Common Pitfalls and Caveats
- Delaying treatment beyond 24 hours significantly reduces efficacy 1, 4
- Acyclovir is not routinely recommended for all healthy children with chickenpox due to minimal morbidity and mortality in this population 6
- Symptomatic treatment alone is usually adequate for uncomplicated chickenpox in immunocompetent individuals 7
- Antiviral therapy does not eliminate the risk of latent virus reactivation (herpes zoster/shingles) later in life 6