Gabapentin Dosing and Administration for Neuropathic Pain and Epilepsy
For neuropathic pain, gabapentin should be initiated at 100-300 mg at bedtime or 100-300 mg three times daily, with gradual titration to 900-3600 mg/day in divided doses over 3-8 weeks. 1, 2
Dosing for Neuropathic Pain
- Start with 100-300 mg at bedtime or 100-300 mg three times daily 1, 2
- Increase by 100-300 mg every 1-7 days as tolerated 1
- Titrate to an effective dose of 900-3600 mg/day in three divided doses 1, 3
- An adequate trial requires 3-8 weeks for titration plus 2 weeks at maximum dose 1, 2
- For postherpetic neuralgia, FDA recommends initiating with 300 mg on day 1,600 mg/day (300 mg twice daily) on day 2, and 900 mg/day (300 mg three times daily) on day 3 4
- Doses of 1800 mg/day are often effective, with limited additional benefit from doses above this level 4, 3
Dosing for Epilepsy
- For adults and patients 12 years and older: Start with 300 mg three times daily 4
- Recommended maintenance dose is 300-600 mg three times daily 4
- Maximum dose is 2400-3600 mg/day in three divided doses 4
- For pediatric patients 3-11 years old: 4
- Starting dose: 10-15 mg/kg/day in three divided doses
- Maintenance dose for ages 3-4 years: 40 mg/kg/day in three divided doses
- Maintenance dose for ages 5-11 years: 25-35 mg/kg/day in three divided doses
Special Populations and Considerations
Renal Impairment
- Dosage adjustment is required for patients with compromised renal function 1, 4
- For creatinine clearance 30-59 mL/min: 400-1400 mg/day in two divided doses 4
- For creatinine clearance 15-29 mL/min: 200-700 mg/day as a single daily dose 4
- For creatinine clearance <15 mL/min: 100-300 mg/day as a single daily dose 4
- Supplemental doses should be administered after hemodialysis 4
Elderly Patients
- Lower starting doses and slower titration are recommended due to higher likelihood of decreased renal function 2, 4
- Consider starting at the lower end of the dosing range (100 mg at bedtime) 1, 2
Administration Guidelines
- Gabapentin can be taken with or without food 4
- The maximum time between doses should not exceed 12 hours 4
- If a scored tablet is divided, the unused half-tablet should be taken as the next dose and discarded if not used within 28 days 4
- Never discontinue gabapentin abruptly; taper gradually over a minimum of 1 week to avoid withdrawal symptoms 4, 5
Efficacy and Adverse Effects
- In postherpetic neuralgia, approximately 32% of patients achieve at least 50% pain relief with gabapentin compared to 17% with placebo 6
- In diabetic neuropathy, about 38% of patients achieve at least 50% pain relief with gabapentin compared to 21% with placebo 6
- Common adverse effects include: 6
- Dizziness (19%)
- Somnolence (14%)
- Peripheral edema (7%)
- Gait disturbance (14%)
- Adverse effects are typically mild to moderate and usually subside within approximately 10 days from treatment initiation 3
Comparison with Pregabalin
- Both medications have similar mechanisms of action but different pharmacokinetic profiles 7
- Gabapentin has nonlinear pharmacokinetics due to saturable absorption, requiring more careful titration 1, 7
- Pregabalin has linear pharmacokinetics, making dosing more straightforward 1, 7
- Pregabalin may provide analgesia more quickly than gabapentin as the initial dose of 150 mg/day has been found efficacious in some trials 1
- Generic gabapentin is typically less expensive than pregabalin 7
Common Pitfalls to Avoid
- Starting at high doses without gradual titration increases the risk of adverse effects 2
- Inadequate trial duration (less than 3-8 weeks for titration plus 2 weeks at maximum dose) may lead to premature discontinuation before efficacy can be properly assessed 1, 2
- Failure to adjust dosing in patients with renal impairment 1, 4
- Abrupt discontinuation can lead to withdrawal symptoms 4, 5
- Using doses above 3600 mg/day, which are not associated with additional benefit but may increase adverse effects 2, 4