What are the typical dosages and uses of gabapentin?

Gabapentin: Dosages and Uses

Gabapentin is primarily used for neuropathic pain and epilepsy, with a recommended starting dose of 300 mg once daily, gradually increasing to 900-3600 mg/day in divided doses, with most patients requiring 1800-3600 mg/day for optimal efficacy. 1, 2

Indications

Neuropathic Pain

• Postherpetic neuralgia
• Painful diabetic neuropathy
• Other neuropathic pain syndromes
• Cancer-related neuropathic pain 3

Epilepsy

• Partial onset seizures (with or without secondary generalization)
• Adjunctive therapy for patients 12 years and older
• Can be used in children 3-11 years 2

Dosing Guidelines

For Neuropathic Pain

1. Initial Titration:

   • Day 1: 300 mg once daily
   • Day 2: 300 mg twice daily (600 mg/day)
   • Day 3: 300 mg three times daily (900 mg/day) 2

2. Effective Dose Range:

   • 1800-3600 mg/day in divided doses
   • Many patients require doses at the higher end for adequate pain control 1
   • Increase gradually by 300 mg every 3-7 days as tolerated 1
   • Allow 2-4 weeks at each dose level to properly assess efficacy 1

For Epilepsy

• Adults and children ≥12 years:

  • Starting dose: 300 mg three times daily
  • Maintenance: 300-600 mg three times daily (900-1800 mg/day)
  • Doses up to 2400 mg/day well tolerated in long-term studies 2

• Children 3-11 years:

  • Starting dose: 10-15 mg/kg/day in three divided doses
  • Maintenance dose:
    • Ages 3-4: 40 mg/kg/day in three divided doses
    • Ages 5-11: 25-35 mg/kg/day in three divided doses 2

Dosage Adjustment for Renal Impairment

Creatinine Clearance (mL/min)	Total Daily Dose Range (mg/day)	Dose Regimen
≥60	900-3600	300-1200 mg TID
>30-59	400-1400	200-700 mg BID
>15-29	200-700	200-700 mg QD
≤15	100-300	100-300 mg QD

Hemodialysis patients require supplemental post-dialysis doses 1, 2

Administration

• Can be taken with or without food
• Maximum time between doses should not exceed 12 hours
• If using scored tablets (600 mg or 800 mg), unused half-tablets should be used for the next dose or discarded after 28 days 2

Efficacy

• For neuropathic pain: 32-38% of patients achieve substantial pain relief (≥50% reduction) compared to 17-21% with placebo 4
• For epilepsy: Effective as adjunctive therapy for partial seizures, with responder rates (≥50% seizure reduction) of 29-44% 5

Common Side Effects

• Dizziness (19%)
• Somnolence (14%)
• Peripheral edema (7%)
• Gait disturbance (14%) 4
• Side effects are typically mild to moderate and often subside within approximately 10 days of treatment initiation 6

Monitoring and Evaluation

• Evaluate response every 2-4 weeks during dose titration
• Assess improvement in pain intensity, function, and quality of life
• Monitor for adverse effects and adjust dose accordingly 1

Special Considerations

• Elderly patients should start with lower doses and titrate more slowly
• Women of reproductive potential should receive counseling regarding contraception, as gabapentin is not recommended during pregnancy 1
• If discontinuing, taper gradually over at least 1 week to avoid withdrawal symptoms 2

Clinical Pearl

Gabapentin is often underdosed in clinical practice. While the FDA-approved dose for postherpetic neuralgia is up to 1800 mg/day, clinical evidence supports that many patients require 2400-3600 mg/day for optimal pain control. Don't hesitate to titrate to higher doses if lower doses are ineffective and the medication is well tolerated 1, 7, 6.