What is the appropriate dosing of gabapentin (Neurontin) for a patient with impaired renal function undergoing dialysis?

Gabapentin Dosing in Dialysis Patients

For patients on hemodialysis, gabapentin should be dosed at 100-300 mg after each dialysis session (typically three times per week). 1

Pharmacokinetics in Renal Impairment

• Gabapentin is exclusively eliminated by renal excretion, with elimination half-life increasing from 5-9 hours in normal renal function to approximately 132 hours in dialysis patients 2
• Hemodialysis effectively removes gabapentin with a clearance of approximately 142 mL/min (about 93% of creatinine clearance), reducing the half-life to approximately 4 hours during dialysis 2
• About 35% of a gabapentin dose is recovered in dialysate during a standard hemodialysis session 2

FDA-Approved Dosing Guidelines

• For patients with creatinine clearance <15 mL/min: 100-300 mg once daily 3
• For hemodialysis patients: Maintenance dose based on creatinine clearance plus supplemental post-hemodialysis dose 3
• Post-hemodialysis supplemental doses range from 125-350 mg depending on the total daily dose 3

Evidence-Based Dosing Recommendations

• The British Association of Dermatologists recommends 100-300 mg after each dialysis session for uremic pruritus 1
• Clinical trials have demonstrated efficacy with:
  • 100 mg post-dialysis three times weekly, showing >50% reduction in pain ratings compared to placebo 1
  • 300 mg three times weekly after dialysis sessions 1
  • 400 mg twice weekly after hemodialysis sessions 1

Risks of Inappropriate Dosing

• Gabapentin toxicity in renal impairment can manifest as:
  • Altered mental status and confusion 4, 5
  • Myoclonus and tremulousness 4
  • Hearing loss (potentially reversible) 4
  • Increased risk of falls and fractures 5

Practical Dosing Algorithm

1. Starting dose: 100-300 mg after each hemodialysis session 1, 3
2. Titration: Increase dose based on clinical response and tolerability
3. Maximum dose: Generally not exceeding 300 mg post-dialysis 1, 3
4. Monitoring: Assess for signs of toxicity including confusion, somnolence, dizziness, and myoclonus 4, 5

Special Considerations

• Plasma gabapentin concentrations may increase by approximately 30% during the first 2 hours after hemodialysis due to drug redistribution 2
• Peritoneal dialysis provides slower but significant clearance of gabapentin (approximately 94% of urea clearance), with an elimination half-life of about 41 hours 6
• For patients transitioning to dialysis who were previously on higher doses, a gradual taper is recommended rather than abrupt dose reduction 3

Common Side Effects in Dialysis Patients

• Drowsiness and dizziness are the most commonly reported adverse effects 1
• Close monitoring is essential during initiation and dose adjustments to minimize these effects 5