What is the recommended use of acyclovir in varicella (chickenpox)?

Acyclovir Use in Varicella (Chickenpox)

Acyclovir is not recommended for routine use in healthy children with varicella, but should be administered to high-risk individuals and those with severe disease within 24 hours of rash onset to reduce morbidity and mortality. 1, 2

Indications for Acyclovir in Varicella

Recommended for:

• Immunocompromised patients - Intravenous acyclovir is essential for reducing mortality and severe disease 1, 3
• Persons aged >12 years - Clinical trials show acyclovir is effective in reducing duration and severity of illness 1, 2
• Individuals with chronic cutaneous or pulmonary disorders 1, 2
• Patients receiving long-term salicylate therapy 1
• Patients on short, intermittent, or aerosolized corticosteroid therapy 1, 2
• Secondary household contacts - Some experts recommend for secondary cases living in the same household 1
• Newborns during first 2 weeks of life and preterm infants in neonatal nurseries 3
• Pregnant women with serious complications (e.g., pneumonia) - Intravenous acyclovir should be considered 1, 2

Not recommended for:

• Routine use in otherwise healthy children - Clinical benefit not sufficient to justify routine administration 1
• Prophylactic use in healthy individuals after varicella exposure - Vaccination is preferred 1, 2
• Asthmatics on aerosolized or low-dose oral steroids 3
• Treatment of post-varicella syndromes 3

Dosing and Administration

Timing:

• Must be administered within 24 hours of rash onset for optimal efficacy 1, 2
• For herpes zoster (shingles), administration within 72 hours is effective 1

Dosage:

• Adults: 800 mg four times daily for 5 days 2
• Children: 20 mg/kg four times daily for 5 days (maximum 800 mg per dose) 2, 4
• Children >40 kg: Use adult dosing 2

Route of administration:

• Intravenous for:
  • Severe disease
  • Patients at risk of dissemination
  • Children younger than 2 years of age 3
  • Immunocompromised patients 5
  • Pregnant women with serious complications 1, 2
• Oral for less severe cases in otherwise healthy individuals at higher risk 1

Clinical Effects and Limitations

Benefits:

• Decreases number of days with new lesions 1, 4
• Reduces duration of fever 1, 4
• Lessens severity of cutaneous and systemic symptoms 1, 4
• In immunocompromised patients, significantly reduces risk of visceral dissemination 5

Limitations:

• Does not decrease transmission of varicella 1
• Does not reduce duration of absence from school 1
• Has not been shown to significantly reduce complications in healthy children (1-2% complication rate) 1
• Does not significantly affect antibody titers long-term 1, 4

Special Considerations

Pregnancy:

• FDA Category B drug 1
• Not recommended for routine use in pregnant women 1
• Data from 596 first-trimester exposures showed birth defect rates similar to general population 1
• Intravenous acyclovir recommended for serious complications like pneumonia 1, 2

Post-exposure prophylaxis:

• Acyclovir is not indicated for prophylaxis in healthy individuals 1, 2
• For immunocompromised patients, varicella-zoster immune globulin (VZIG) is recommended instead 1, 2
• Some evidence suggests acyclovir or valacyclovir may be used when the window for VZIG has expired 6

Clinical Pitfalls to Avoid

• Delayed treatment - Efficacy significantly reduced if not started within 24 hours of rash onset
• Undertreatment of high-risk groups - Immunocompromised patients require aggressive IV therapy
• Overuse in healthy children - Unnecessary treatment increases costs without significant clinical benefit
• Relying on acyclovir for prophylaxis - Vaccination is the preferred method for prevention in healthy individuals
• Oral administration in severe cases - IV route is necessary for severe disease and in young children