Acyclovir Dosing for Varicella in a 69-Year-Old Patient
For a 69-year-old adult with chickenpox and normal renal function, the recommended dose is acyclovir 800 mg orally four times daily for 5 days, initiated within 24 hours of rash onset. 1
Standard Dosing Regimen
- The FDA-approved dose for chickenpox treatment in adults is 800 mg orally 4 times daily for 5 days 1
- Treatment should be initiated at the earliest sign or symptom of chickenpox, ideally within 24 hours of rash onset 1
- There is no information about efficacy when therapy is initiated more than 24 hours after onset of signs and symptoms 1
Critical Timing Considerations
- Early initiation is essential: Acyclovir reduces acute chickenpox symptoms including fewer lesions, shorter duration of new lesion formation, and reduced fever when started within 24 hours of rash onset 2
- The therapeutic window is narrow—treatment effectiveness diminishes significantly if delayed beyond 24 hours 1
Age-Related Risk Factors
At 69 years of age, this patient is at increased risk for moderate to severe varicella and complications, making antiviral treatment particularly important 2. Older adults experience more severe disease with higher rates of complications including pneumonitis and disseminated infection.
Renal Function Monitoring
Since you specified normal renal function, no dose adjustment is needed 1. However, be aware that:
- If creatinine clearance is 25-50 mL/min: reduce to 800 mg every 8 hours 1
- If creatinine clearance is 10-25 mL/min: reduce to 800 mg every 8 hours 1
- If creatinine clearance is 0-10 mL/min: reduce to 800 mg every 12 hours 1
- Acyclovir neurotoxicity can occur with standard dosing in renal failure, presenting as confusion, hallucinations, or seizures 3
Alternative Considerations
While the question asks specifically about acyclovir, valacyclovir (1,000 mg three times daily for 7 days) is an alternative with simpler dosing and improved bioavailability 4. However, for varicella specifically, the FDA label supports the 800 mg four times daily acyclovir regimen 1.
Immunocompromised Patients
If this patient were immunocompromised (not specified in your question), intravenous acyclovir would be indicated rather than oral therapy 1, 5. The KDIGO guidelines recommend either intravenous or oral acyclovir for primary VZV infection in kidney transplant recipients, with treatment continued until all lesions have scabbed 5.
Common Pitfall to Avoid
Do not use the herpes zoster dosing regimen (800 mg 5 times daily) for chickenpox—the FDA-approved chickenpox regimen is 800 mg 4 times daily for 5 days 1. This is a frequent prescribing error.