Acyclovir Dosing for Stage 3 CKD
For patients with Stage 3 CKD (creatinine clearance 30-59 mL/min), acyclovir requires dose adjustment: use 200-800 mg every 8 hours for oral dosing or 5-10 mg/kg IV every 12 hours, depending on the indication. 1
Specific Dosing by Indication and Renal Function
Stage 3A CKD (CrCl 45-59 mL/min)
- Herpes zoster: 800 mg orally every 4 hours, 5 times daily (standard dosing may be appropriate at higher end of Stage 3A) 1
- Genital herpes treatment: 200 mg every 4 hours, 5 times daily 1
- Genital herpes suppression: 400 mg every 12 hours 1
- IV dosing: 5-10 mg/kg every 8-12 hours depending on severity 2
Stage 3B CKD (CrCl 30-44 mL/min)
- Herpes zoster: 800 mg orally every 8 hours 1
- Genital herpes: 200 mg every 8 hours or 200-800 mg three times daily 2, 1
- IV dosing: 5-10 mg/kg every 12 hours 2, 1
Stage 3 Borderline (CrCl 25-29 mL/min)
Critical Clinical Considerations
Neurotoxicity risk increases substantially with inadequate dose adjustment in renal impairment. 3, 4 The FDA label explicitly requires dose modification based on creatinine clearance to prevent serious neurological complications including confusion, ataxia, and altered mental status 1, 3.
Key Safety Points:
- Calculate creatinine clearance accurately before prescribing—do not rely on serum creatinine alone 5, 6
- Monitor renal function during therapy, as acyclovir can occasionally cause acute renal failure 7
- Ensure adequate hydration to prevent acyclovir crystalluria and nephrotoxicity 1
- Watch for neuropsychiatric symptoms (confusion, hallucinations, tremors) which indicate potential toxicity 3, 4, 8
Dosing Algorithm Summary
The FDA-approved dosing table provides clear guidance 1:
- CrCl >25 mL/min: 800 mg every 4 hours (5x daily) for herpes zoster
- CrCl 10-25 mL/min: 800 mg every 8 hours
- CrCl 0-10 mL/min: 800 mg every 12 hours
For lower-dose regimens (200-400 mg), adjustments are proportionally less aggressive but still required 1.
Common Pitfalls to Avoid
The most dangerous error is using standard dosing in patients with unrecognized renal impairment. 3 Case reports document severe neurotoxicity, including one patient on hemodialysis who received standard dosing and developed progressive confusion and ataxia 3. Another case showed neurotoxicity even with dose reduction, emphasizing the need for precise calculation 4.
Acyclovir and its metabolites accumulate in both plasma and CSF when renal function is impaired, with concentrations proportionally higher in patients with CrCl 15-30 mL/min compared to normal function 8. This pharmacokinetic reality underlies the absolute requirement for dose adjustment in Stage 3 CKD 5, 8.