What is the starting dose of gabapentin (Neurontin) for adults?

Starting Dose of Gabapentin for Adults

The recommended starting dose of gabapentin for adults is 300 mg once daily on day 1, then 300 mg twice daily on day 2, and 300 mg three times daily (900 mg/day) on day 3. 1, 2

Dosing Guidelines by Indication

Neuropathic Pain

• Initial titration schedule:
  • 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)
• Target dose: 1800-3600 mg/day in divided doses
• Maximum dose: 3600 mg/day 1, 2

Postherpetic Neuralgia

• Follow the same initial titration as above
• Effective dose range: 1800-3600 mg/day
• FDA-approved maintenance dose: 1800 mg/day (600 mg three times daily)
• Higher doses (up to 3600 mg/day) may be needed in some patients but additional benefit beyond 1800 mg/day has not been clearly demonstrated 1

Epilepsy (Partial Onset Seizures)

• Adults and patients ≥12 years: Start with 300 mg three times daily
• Maintenance dose: 300-600 mg three times daily (900-1800 mg/day)
• Maximum dose: 2400-3600 mg/day 1

Dosage Adjustments

Renal Impairment

Dosage adjustment is required based on creatinine clearance:

• CrCl ≥60 mL/min: 900-3600 mg/day (300 mg TID to 1200 mg TID)
• CrCl 30-59 mL/min: 400-1400 mg/day (200-700 mg BID)
• CrCl 15-29 mL/min: 200-700 mg/day (200-700 mg QD)
• CrCl <15 mL/min: 100-300 mg/day (100-300 mg QD) 1

Elderly Patients

• Start at the lower end of the dosing range
• Adjust based on renal function, which is often decreased in elderly patients 1

Administration Guidelines

• Gabapentin can be taken with or without food
• Maximum time between doses should not exceed 12 hours
• For divided tablets (600 mg or 800 mg), unused half-tablets should be used for the next dose and discarded if not used within 28 days 1

Special Considerations

Unexplained Chronic Cough

For patients with unexplained chronic cough, a therapeutic trial of gabapentin may be considered:

• Start at 300 mg once daily
• Gradually increase to a maximum tolerable daily dose of 1800 mg in two divided doses 3

Efficacy and Tolerability

• Moderate to substantial pain relief is achieved in approximately 30-50% of patients with neuropathic pain conditions 4
• Common adverse effects include dizziness (19%), somnolence (14%), peripheral edema (7%), and gait disturbance (14%) 4
• Adverse effects are typically mild to moderate and usually subside within approximately 10 days from treatment initiation 5

Pitfalls to Avoid

• Inadequate dosing: Many patients require at least 1800 mg/day for effective pain relief
• Too rapid titration: Can increase side effects and lead to poor tolerance
• Abrupt discontinuation: Gabapentin should be tapered gradually over at least 1 week to avoid withdrawal symptoms 1
• Failure to adjust for renal impairment: Can lead to toxicity in patients with decreased renal function

By following this structured approach to gabapentin dosing, clinicians can optimize efficacy while minimizing adverse effects for adult patients requiring this medication.