What is the recommended dosage and treatment protocol for gabapentin (Neurontin) for neuropathic pain?

Gabapentin Dosing Protocol for Neuropathic Pain

For neuropathic pain, gabapentin should be initiated at 100-300 mg at bedtime or 100-300 mg three times daily, with gradual titration over 1-7 days as tolerated, up to an effective dose range of 900-3600 mg/day in 3 divided doses. 1, 2, 3

Initial Dosing and Titration

• Start gabapentin at 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
• Consider a more conservative approach for elderly patients or those with renal impairment: slower titration with lower doses 2, 3
• For postherpetic neuralgia, FDA labeling specifically recommends initiating with a single 300 mg dose on Day 1,300 mg twice daily on Day 2, and 300 mg three times daily on Day 3 3

Effective Dosage Range and Administration

• Effective dosage range: 900-3600 mg/day in 3 divided doses 1, 2, 3
• Most patients require 1800-3600 mg/day for optimal pain relief 1, 4
• Maximum time between doses should not exceed 12 hours to maintain therapeutic levels 2, 3
• An adequate trial requires at least 3-8 weeks for titration plus 2 weeks at maximum tolerated dose 1

Dosage Adjustment for Renal Impairment

• Dosage must be reduced in patients with compromised renal function 1, 3
• For creatinine clearance 30-59 mL/min: 400-1400 mg/day in divided doses 3
• For creatinine clearance 15-29 mL/min: 200-700 mg/day in divided doses 3
• For creatinine clearance <15 mL/min: 100-300 mg once daily 3
• Supplemental doses required after hemodialysis 3

Efficacy and Expectations

• In postherpetic neuralgia, approximately 32% of patients achieve at least 50% pain relief with gabapentin compared to 17% with placebo 4
• In diabetic neuropathy, about 38% of patients achieve at least 50% pain relief with gabapentin compared to 21% with placebo 4
• Gabapentin has shown efficacy for various neuropathic pain syndromes including allodynia, burning pain, shooting pain, and hyperalgesia 5, 6
• Pain relief may begin within days but optimal effects typically require several weeks of treatment 6, 7

Common Side Effects and Management

• Most common adverse effects: dizziness (19%), somnolence (14%), peripheral edema (7%), and gait disturbance (14%) 4
• Side effects are typically mild to moderate and often transient, usually subsiding within approximately 10 days of treatment initiation 6
• Adverse effects can be minimized by starting with lower dosages and titrating cautiously 1
• About 11% of patients discontinue gabapentin due to adverse events compared to 8.2% with placebo 4

Clinical Pearls

• Nonlinear pharmacokinetics (due to saturable absorption) necessitate careful titration 1
• If 1800 mg/day is ineffective after an adequate trial, consider increasing to 3600 mg/day, as some patients require higher doses 1, 6
• For patients who cannot tolerate gabapentin, consider pregabalin which has similar efficacy but linear pharmacokinetics and more straightforward dosing 1
• Pregabalin can be started at 50 mg three times daily or 75 mg twice daily and titrated to 300-600 mg/day 1
• Gabapentin is generally well-tolerated and can be safely combined with other pain medications 7