Gabapentin Dosing for Sciatica
Start gabapentin at 100-300 mg at bedtime on day 1, increase to 300 mg three times daily by day 3, then titrate by 300 mg every 3-7 days to reach a target dose of 1800-3600 mg/day in three divided doses. 1, 2
Critical Context: Limited Evidence for Sciatica Specifically
- Gabapentin lacks high-quality evidence specifically for sciatica, with only case reports demonstrating efficacy at doses of 900-1800 mg/day (300-600 mg three times daily). 3
- However, gabapentin has proven efficacy for other neuropathic pain conditions (postherpetic neuralgia, diabetic neuropathy) at similar dosing regimens, providing a reasonable framework for sciatica treatment. 4, 5
- The case reports suggest gabapentin may prevent central sensitization in sciatica, supporting early initiation in the disease course. 3
Standard Titration Protocol
Initial Phase (Days 1-3):
- Day 1: Start 100-300 mg at bedtime 1, 2
- Day 3: Increase to 100-300 mg three times daily (300-900 mg/day total) 1, 2
Titration Phase (Weeks 1-8):
- Increase by 100-300 mg every 3-7 days as tolerated 1, 2
- Target minimum effective dose: 1800 mg/day (600 mg three times daily) 2
- Maximum dose: 3600 mg/day (1200 mg three times daily) 1, 2
Trial Duration:
- Allow 3-8 weeks for titration plus 2 weeks at maximum tolerated dose before declaring treatment failure 1, 2
- Full therapeutic trial may require 2 months or more 1
Mandatory Three-Times-Daily Dosing
- Gabapentin must be dosed three times daily due to nonlinear, saturable absorption—once or twice daily dosing is inadequate. 2
- Doses should be spaced no more than 12 hours apart. 1
Renal Function Assessment (Non-Negotiable)
- Calculate creatinine clearance using Cockcroft-Gault equation before initiating therapy, as gabapentin is renally excreted. 1
- Mandatory dose reduction required for renal impairment:
Expected Efficacy Based on Neuropathic Pain Data
- In validated neuropathic pain conditions, 32-38% of patients achieve at least 50% pain reduction with gabapentin 1800-3600 mg/day versus 17-21% with placebo. 5
- The NNT for substantial benefit (≥50% pain relief) is approximately 6-8 in postherpetic neuralgia and diabetic neuropathy. 5, 6
- Pain relief develops gradually over several weeks, not immediately. 2
Common Adverse Effects and Management
- Dizziness (19%), somnolence (14%), peripheral edema (7%), and gait disturbance (9%) are the most common side effects. 1, 5
- These effects are typically mild to moderate, dose-dependent, and often transient, usually subsiding within approximately 10 days. 1
- Adverse event withdrawals occur in 11% versus 8.2% with placebo (NNH 30). 1, 5
Critical Pitfalls to Avoid
- Never start at high doses (such as 800 mg four times daily) without gradual titration—this dramatically increases intolerable adverse effects, particularly in elderly patients. 1
- Do not fail to assess renal function before initiating therapy—this is mandatory given gabapentin's renal excretion. 1
- Avoid abrupt discontinuation—taper gradually over at least 1 week to prevent withdrawal symptoms. 1, 2
- Do not assume lack of efficacy if adequate time has not been allowed—full therapeutic trial requires 2+ months. 1, 2
- Lower starting doses (100-200 mg/day) and slower titration are essential in elderly patients to minimize fall risk from dizziness. 1, 2
Alternative: Pregabalin as Superior Option
- Pregabalin may be preferable to gabapentin due to linear pharmacokinetics (more predictable dosing), faster onset of pain relief (within 1 week versus 4+ weeks), and simpler twice-daily dosing. 1, 7
- Pregabalin dosing: Start 75 mg twice daily, increase to 150 mg twice daily (300 mg/day) within 1 week, with maximum 600 mg/day reserved for inadequate responders. 7
- However, pregabalin has similar adverse effect profile (dizziness, somnolence, peripheral edema) and lacks specific evidence for sciatica. 7