Aciclovir Treatment Guidelines for Chickenpox
For patients with chickenpox, aciclovir should be administered at a dose of 20 mg/kg body weight orally per dose (maximum 800 mg/dose) 4 times daily for 7-10 days or until no new lesions appear for 48 hours. 1
Dosing Recommendations by Age Group
Children
- Children <45 kg: Aciclovir 20 mg/kg body weight (maximum 400 mg/dose) per dose orally 3-4 times daily for 5-10 days 1
- Treatment is most effective when initiated within the first 24 hours of rash onset 2, 3
- Five days of therapy is generally sufficient, as longer courses provide no additional benefit 2
Adolescents and Adults
- Adults and adolescents: Aciclovir 800 mg orally 4-5 times daily for 7-10 days 1
- Clinical trials have shown aciclovir is well-tolerated and effective in reducing duration and severity of illness when administered within 24 hours of rash onset 1
Clinical Considerations for Treatment
When to Use Aciclovir
- Treatment should be considered for:
- Patients >12 years of age 1
- Patients with chronic cutaneous or pulmonary disorders 1
- Patients receiving long-term salicylate therapy 1
- Patients receiving short, intermittent, or aerosolized courses of corticosteroids 1
- Secondary household contacts of infected children 1
- Immunocompromised patients (who may require higher doses or IV formulations) 4
Timing of Treatment
- Maximum benefit occurs when treatment is initiated within 24 hours of rash onset 2, 3
- Some benefit may still be observed when treatment is initiated within 48 hours of rash onset, though with diminished efficacy 2
- After 48 hours from rash onset, benefits are significantly reduced 2
Clinical Benefits
- Reduces number of varicella lesions (mean 294 vs 347 with placebo) 3
- Accelerates progression to crusted and healed stages 3
- Reduces duration of fever and constitutional symptoms to 3-4 days 3
- Decreases itching and residual lesions after 28 days 3
- Prevents formation of new lesions after day 3 in over 95% of treated patients 3
Special Populations
Immunocompromised Patients
- For immunocompromised patients with severe disease or at high risk for complications, intravenous aciclovir should be considered 1, 5
- Dose: 10 mg/kg body weight IV 3 times daily 1
- Some experts base IV aciclovir dosing in children >1 year on body surface area (500 mg/m²/dose IV every 8 hours) 1
Pregnancy
- Aciclovir is classified as Category B in FDA pregnancy rating 1
- Routine use during pregnancy is not generally recommended as risks and benefits to fetus and mother must be carefully weighed 1
- For serious viral-mediated complications during pregnancy (e.g., pneumonia), intravenous aciclovir should be considered 1
Post-Exposure Prophylaxis
- Aciclovir is not indicated for prophylactic use in healthy individuals after exposure to varicella 1
- For susceptible immunocompromised patients, zoster immune globulin within 96 hours of exposure is recommended rather than aciclovir 1
- For those without access to vaccination who are exposed to chickenpox, a 7-day course of aciclovir starting 7 days after exposure may be considered 1
Adverse Effects
- Most common adverse effects include nausea/vomiting (2.7%), diarrhea (3.2%), and malaise (11.5%) 6
- Maintain adequate hydration and urine flow during treatment, especially with higher doses 5
- Monitor mental status in patients receiving high doses 5
Important Caveats
- Aciclovir does not eradicate latent virus or affect subsequent risk, frequency, or severity of recurrences 4
- Viral resistance has not been observed in immunocompetent patients treated with standard courses 2
- Antibody titers after infection in children receiving aciclovir do not differ substantially from those not receiving treatment 1