What is the recommended dose of gabapentin (Gabapentin) for a patient with impaired renal function, specifically a Glomerular Filtration Rate (GFR) of 30?

Gabapentin Dosing for Patients with GFR 30 mL/min/1.73m²

For patients with a GFR of 30 mL/min/1.73m², the recommended gabapentin dosage is 200-700 mg/day, administered as 200-300 mg once daily (QD). 1

Dosing Rationale and Pharmacokinetics

Gabapentin is exclusively eliminated by the kidneys, making dose adjustment essential in patients with impaired renal function. The FDA-approved labeling provides clear guidance for dosing based on creatinine clearance:

• For patients with creatinine clearance >30-59 mL/min: 400-1400 mg/day (divided BID)
• For patients with creatinine clearance >15-29 mL/min: 200-700 mg/day (administered QD)

Since a GFR of 30 mL/min falls at the border between these categories, the more conservative approach (200-700 mg/day as a single daily dose) is appropriate to prevent toxicity.

Clinical Considerations

Risk of Toxicity

Gabapentin toxicity is significantly higher in patients with reduced renal function:

• Elimination half-life increases from 5-9 hours in normal renal function to up to 132 hours in patients with severe renal impairment 2
• Patients with chronic kidney disease often receive inappropriately high gabapentin doses, leading to toxicity 3

Signs of Toxicity to Monitor

• Altered mental status
• Myoclonus or tremors
• Dizziness
• Somnolence
• Ataxia

Special Considerations

• Elderly patients with multiple comorbidities are at higher risk for gabapentin toxicity 3
• Gabapentin toxicity is frequently underrecognized in clinical practice, with initial suspicion in only 41.5% of symptomatic cases 3
• Plasma gabapentin concentrations increase linearly as renal function declines 4

Monitoring Recommendations

• Regular assessment of renal function
• Monitor for signs of toxicity, especially during dose initiation or adjustment
• Consider drug level monitoring in high-risk patients or those showing potential signs of toxicity
• Reassess dosing if renal function changes

Practical Dosing Algorithm

1. Start with 100-200 mg once daily
2. If needed and tolerated, may increase to 300 mg once daily after 2-3 days
3. Maximum daily dose should not exceed 700 mg/day
4. If the patient experiences adverse effects, reduce the dose or increase the dosing interval
5. If renal function worsens (GFR <15 mL/min), further reduce the dose in proportion to the decrease in creatinine clearance

This conservative dosing approach prioritizes patient safety while still allowing for effective symptom management in patients with significantly impaired renal function.