Gabapentin for Neuropathic Pain
Gabapentin is an effective first-line treatment option for neuropathic pain, particularly for postherpetic neuralgia and painful diabetic neuropathy, where approximately 35-38% of patients achieve at least 50% pain reduction compared to 17-21% with placebo. 1, 2
Evidence for Efficacy
Gabapentin demonstrates moderate-quality evidence for specific neuropathic pain conditions:
Postherpetic neuralgia: 32% achieve substantial benefit (≥50% pain relief) versus 17% with placebo (NNT 6.7), and 46% achieve moderate benefit (≥30% pain relief) versus 25% with placebo (NNT 4.8) 3, 2
Painful diabetic neuropathy: 38% achieve substantial benefit versus 21% with placebo (NNT 5.9), and 52% achieve moderate benefit versus 37% with placebo (NNT 6.6) 3, 2
HIV-associated neuropathic pain: Gabapentin is specifically recommended as first-line oral pharmacological treatment 1, 4
Optimal Dosing Strategy
Start gabapentin at 100-300 mg at bedtime on day 1, increase to 600 mg/day on day 2, then 900 mg/day on day 3, with further titration to 1800-3600 mg/day in 2-3 divided doses based on response. 1, 5
Doses of 1800-3600 mg/day are required for efficacy; lower doses used in clinical practice often result in suboptimal outcomes 4, 5
Do not exceed 3600 mg/day as there is no evidence of additional benefit and adverse effects increase 6
Allow at least 2 weeks at therapeutic dose before assessing efficacy 1
Special Populations
For older adults, start with the lowest doses (100-200 mg/day) due to increased risk of somnolence, dizziness, and mental clouding. 4
Adjust doses in renal impairment based on creatinine clearance 1, 4
Gabapentin has minimal systemic absorption and low toxicity profile, making it suitable for elderly patients 4
Adverse Effects Profile
Expect the following adverse events with gabapentin:
- At least one adverse event: 62% versus 49% with placebo (NNH 7.5) 2
- Dizziness: 19% of patients 2
- Somnolence: 14% of patients 2
- Peripheral edema: 7% of patients 2
- Gait disturbance: 14% of patients 2
- Withdrawal due to adverse events: 11% versus 8.2% with placebo (NNH 30) 2
Serious adverse events (3%) are no more common than placebo, and adverse effects typically subside within approximately 10 days from initiation 2, 5
Conditions with Limited or No Evidence
Gabapentin has insufficient evidence or is relatively refractory in:
- Lumbosacral radiculopathy (recent trials show limited efficacy) 1
- Chemotherapy-induced peripheral neuropathy (no evidence of efficacy in RCTs) 1
- HIV-associated neuropathy may be relatively refractory compared to other conditions 1
When Gabapentin Fails
If inadequate response after adequate trial (≥1800 mg/day for at least 2 weeks), switch to duloxetine 60-120 mg daily or add an antidepressant (duloxetine or tricyclic) for combination therapy. 6
Combination of gabapentin with an antidepressant provides superior pain relief compared to either medication alone 1
Consider adding capsaicin 8% dermal patch (single 30-minute application provides relief for ≥12 weeks) 6
Never abruptly discontinue gabapentin—taper gradually over minimum 1 week (reduce by 10% of original dose per week) to avoid withdrawal symptoms 6
Critical Caveats
Over half of patients treated with gabapentin will not achieve worthwhile pain relief 2, 7
Gabapentin is prescribed 8-fold more than duloxetine despite inferior evidence, suggesting potential overuse 6
The outcome of ≥50% pain reduction is associated with important beneficial effects on sleep interference, fatigue, depression, quality of life, function, and work 2, 7
Gabapentin relieves symptoms of allodynia, burning pain, shooting pain, and hyperesthesia 5