Starting Dose of Gabapentin for Adults
The recommended starting dose of gabapentin for adults is 300 mg on day 1, which can be initiated as a single nightly dose. 1, 2
Dosing Algorithm
Initial Dosing
- Day 1: 300 mg once daily (typically at bedtime)
- Day 2: 600 mg/day (300 mg twice daily)
- Day 3: 900 mg/day (300 mg three times daily)
Titration Schedule
- Increase by 300 mg/day every 3-7 days as tolerated
- Dose increments of 50-100% can be made every few days 1
- Target maintenance dose: 900-3600 mg/day in divided doses (2-3 times daily) 1, 2
Special Populations
- Elderly patients: Use slower titration and consider lower starting doses 1, 2
- Medically frail patients: Use slower titration 1
- Renal impairment: Dose adjustment required based on creatinine clearance 2:
- CrCl ≥60 mL/min: Standard dosing
- CrCl 30-59 mL/min: 400-1400 mg/day
- CrCl 15-29 mL/min: 200-700 mg/day
- CrCl <15 mL/min: 100-300 mg/day
Efficacy Considerations
- Effective dose range is typically 900-3600 mg/day 1, 2
- In postherpetic neuralgia, doses of 1800-3600 mg/day have demonstrated efficacy 2, 3
- For neuropathic pain, doses of 1800-3600 mg/day are often needed for optimal pain relief 4, 3
- Maximum time between doses should not exceed 12 hours 2
Common Pitfalls and Caveats
Underdosing: Starting at too low a dose or failing to titrate to an effective dose may result in inadequate pain relief. While 300 mg is the appropriate starting dose, many patients require at least 1800 mg/day for meaningful pain reduction 4, 3.
Too rapid titration: Increasing the dose too quickly can lead to increased adverse effects such as dizziness and somnolence, which may be transient but can affect adherence 5.
Inadequate trial duration: An adequate trial of gabapentin may require 2 months or more to determine efficacy 1.
Renal function assessment: Failing to adjust dosing based on renal function can lead to toxicity in patients with impaired renal clearance 2.
Divided dosing importance: Administering gabapentin in divided doses (typically three times daily) is important for maintaining therapeutic levels due to its relatively short half-life 2.
Gabapentin is generally well-tolerated, but common adverse effects include dizziness (19%), somnolence (14%), peripheral edema (7%), and gait disturbance (14%) 3. Most adverse effects are mild to moderate and typically subside within approximately 10 days from treatment initiation 4.