What is the recommended dose of aciclovir (antiviral medication) for treating chickenpox?

Recommended Acyclovir Dosage for Chickenpox

For chickenpox treatment, acyclovir should be administered at 20 mg/kg per dose (maximum 800 mg per dose) orally 4 times daily for 5 days. 1

Dosing Guidelines by Patient Population

Children (under 40 kg)

• Dose: 20 mg/kg per dose
• Frequency: 4 times daily
• Duration: 5 days
• Maximum daily dose: 80 mg/kg/day 1

Adults and Children over 40 kg

• Dose: 800 mg per dose
• Frequency: 4 times daily
• Duration: 5 days 1

Immunocompromised Patients

• For patients with severe immunosuppression:
  • Consider intravenous acyclovir instead of oral therapy 2
  • Dose: 10 mg/kg body weight IV every 8 hours
  • Duration: 7-10 days 2

Timing of Treatment Initiation

Treatment is most effective when initiated within the first 24 hours of rash onset 3, 4. Research shows:

• Starting treatment on day 1 of rash provides maximum benefit
• Starting on day 2 still offers some benefit but is less effective
• Limited benefit if started after 48 hours of rash onset 3

Special Considerations

Renal Impairment

Dose adjustment is necessary for patients with renal impairment:

• Creatinine clearance >10 mL/min/1.73m²: Standard dose
• Creatinine clearance 0-10 mL/min/1.73m²: 200 mg every 12 hours 1

Hemodialysis

• Administer an additional dose after each dialysis session 1

Monitoring

• Maintain adequate hydration to reduce the risk of nephropathy
• Monitor renal function during treatment, especially with prolonged courses

Treatment Efficacy

Clinical studies demonstrate that acyclovir treatment for chickenpox:

• Reduces the number of lesions (294 vs 347 with placebo) 4
• Accelerates healing of lesions 4
• Shortens duration of fever (1 day vs 2 days with placebo) 5
• Reduces itching and constitutional symptoms 4

Common Pitfalls to Avoid

1. Delayed initiation: Starting treatment after 24 hours significantly reduces efficacy. Treatment should begin at the earliest sign of chickenpox rash 3.

2. Incorrect dosing: Using adult dosing for children can lead to inadequate treatment. Always calculate pediatric doses based on weight (20 mg/kg) 1.

3. Extended treatment: Five days of therapy is sufficient; longer treatment provides no additional benefit 3.

4. Inadequate hydration: Ensure proper hydration during treatment to prevent nephrotoxicity.

5. Missing immunocompromised status: Standard oral therapy may be inadequate for immunocompromised patients, who often require IV acyclovir 2.

For prophylaxis after exposure to chickenpox in susceptible patients, oral acyclovir at 10 mg/kg four times daily for 7 days can be considered if initiated within 7-10 days of exposure 2.