Acyclovir Prophylaxis Dosing in Hemodialysis Patients
For hemodialysis patients requiring acyclovir prophylaxis, administer 200 mg orally every 12 hours, with the first daily dose given after dialysis. 1, 2
Oral Prophylaxis Dosing
The recommended prophylactic dose for hemodialysis patients is 200 mg orally every 12 hours. 1, 2 This represents a substantial reduction from the standard 200 mg five times daily used in patients with normal renal function, reflecting the dramatically prolonged half-life of acyclovir in end-stage renal disease (approximately 20 hours versus 2-3 hours in normal renal function). 3, 4
Timing Considerations
Administer the first daily dose immediately after hemodialysis sessions to replace drug removed during dialysis, as hemodialysis eliminates approximately 60% of circulating acyclovir over a 6-hour session. 1, 2, 4
On non-dialysis days, maintain the every 12-hour dosing schedule without supplementation. 2
Alternative Dosing Strategies
For patients requiring higher therapeutic levels (treatment rather than prophylaxis):
- Loading dose: 400 mg orally after dialysis 3, 5
- Maintenance: 200 mg orally twice daily 3, 5
- Post-dialysis supplementation: Additional 400 mg after each dialysis session 3
This regimen maintains mean plasma levels of approximately 6.4 μM, which falls within the therapeutic range of 4-8 μM needed to inhibit herpes viruses. 3
Critical Safety Warnings
The standard dose of 800 mg twice daily used in patients with normal renal function causes acute neurotoxicity in dialysis patients and must never be used. 3, 5 Neurotoxicity has been documented even with doses as low as 800 mg daily in this population. 6, 5
Signs of Acyclovir Neurotoxicity
- Confusion, hallucinations, agitation 3, 5
- Tremors, myoclonus, seizures 3, 5
- Lethargy progressing to coma 5
Management of Suspected Toxicity
If neurotoxicity is suspected, immediately discontinue acyclovir and perform urgent hemodialysis, which serves as both diagnostic confirmation and therapeutic intervention by rapidly clearing the drug (half-life during dialysis: 5.7 hours). 3, 4
Pharmacokinetic Rationale
The dramatic dose reduction is necessary because:
- Terminal half-life increases from 2-3 hours to 19.5 hours in anuric patients 4, 7
- Total body clearance decreases to 28.6 ml/min/1.73 m² compared to normal renal clearance 4
- Peak plasma levels are twice as high in end-stage renal disease patients compared to those with normal renal function at equivalent doses 7
- Hemodialysis removes acyclovir efficiently with an extraction ratio of 0.44-0.45 and dialysis clearance of 82-113 ml/min 4, 7
Intravenous Alternative
If intravenous administration is required:
- For CrCl <10 mL/min or hemodialysis: 2.5-5 mg/kg IV every 24 hours 1
- Administer post-dialysis on dialysis days 1
- Infuse slowly over 1 hour with adequate hydration (at least 1.5 liters daily) to prevent nephrotoxicity 1
Peritoneal Dialysis Patients
For continuous ambulatory peritoneal dialysis (CAPD) patients, the recommended dose is 600-800 mg orally daily (divided into 200 mg three times daily or 400 mg twice daily), as peritoneal dialysis removes acyclovir less efficiently than hemodialysis. 6, 5 The standard 1,600 mg daily dose leads to supratherapeutic levels and neurotoxicity risk in this population. 6