Gabapentin Dosing for Fibromyalgia
For fibromyalgia, gabapentin should be initiated at 300 mg at bedtime, gradually titrated to a target effective dose of 1800 mg/day (divided into 3 doses), with a maximum dose of 2400 mg/day if needed. 1
Initial Dosing and Titration Schedule
- Starting dose: 300 mg at bedtime or 100-300 mg three times daily 1
- Titration: Increase by 300 mg every 3-7 days as tolerated 1
- Target effective dose: 1800 mg/day (600 mg three times daily) 1
- Maximum dose: 2400 mg/day for fibromyalgia 2
Dosing Considerations
Efficacy and Risk Profile
- 900-1800 mg/day: Effective for most patients with lower risk of adverse effects 1
- 1800-2400 mg/day: Modest additional benefit with increased risk of adverse effects 1
- 2400-3600 mg/day: Minimal additional benefit with significantly higher risk of falls, fractures, and edema 1
Evidence for Efficacy
- In a randomized, double-blind, placebo-controlled trial, gabapentin at doses of 1200-2400 mg/day demonstrated significant improvement in pain scores compared to placebo 2
- 51% of patients on gabapentin achieved at least 30% pain reduction compared to 31% on placebo 2
- Cochrane review indicates limited evidence with only one high-quality study showing efficacy 3
Administration Guidelines
- Frequency: Divide daily dose into three administrations to improve tolerability 1
- Timing: Take with food to minimize side effects 1
- Duration of trial: An adequate trial requires 3-8 weeks for titration plus 2 weeks at maximum dose before determining efficacy 1
Side Effect Management
- Common side effects: Dizziness (19%), somnolence (14%), peripheral edema (7%), and gait disturbance (14%) 1
- Minimizing side effects:
- Start with lower dosages
- Titrate cautiously
- Take medication with food
- Use nighttime dosing for sedating effects 1
Special Populations
- Elderly patients: Start at lower doses (100-300 mg at bedtime) and titrate more slowly 1
- Renal impairment: Dose adjustment required based on creatinine clearance 1
- CrCl 30-59 mL/min: Maximum 700 mg at bedtime
- CrCl 15-29 mL/min: Maximum 700 mg at bedtime
- CrCl <15 mL/min: Maximum 300 mg at bedtime
Discontinuation
- Taper gradually over at least 1 week to avoid withdrawal symptoms 1
- Recommended tapering schedule:
- 300 mg at bedtime for 1-3 days
- 300 mg twice daily for 1-3 days
- 300 mg three times daily before further reduction 1
Clinical Pearls
- Gabapentin has nonlinear pharmacokinetics due to saturable absorption, necessitating divided dosing 1
- While pregabalin has more robust evidence for fibromyalgia treatment 4, gabapentin remains a viable alternative
- Extended-release gabapentin formulations may improve sleep quality and quantity in fibromyalgia patients 5
- Consider that only about 10% more patients will achieve significant pain relief with gabapentin compared to placebo 3