Gabapentin Starting Dose for Adults
The typical starting dose of gabapentin for adults is 300 mg once daily on day 1, increasing to 300 mg twice daily on day 2, and 300 mg three times daily (900 mg/day) on day 3. 1
Dosing Guidelines by Indication
Postherpetic Neuralgia
- 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)
- Can be titrated up to 1800 mg/day (600 mg three times daily) as needed for pain relief 1
- Higher doses up to 3600 mg/day have been administered but showed no additional benefit over 1800 mg/day 1
Epilepsy (Partial Onset Seizures)
- Adults and patients ≥12 years: 300 mg three times daily (900 mg/day) initially
- Maintenance dose: 300-600 mg three times daily (900-1800 mg/day)
- Maximum dose: 2400 mg/day (well-tolerated in long-term studies) 1
Neuropathic Pain
- Start at 300 mg on day 1,600 mg on day 2, and 900 mg on day 3 2
- Titrate to 1800 mg/day for better efficacy
- Some patients may require up to 3600 mg/day 2
Dosage Adjustment for Renal Impairment
Renal function significantly impacts gabapentin clearance, requiring dose adjustment 1, 3:
| 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 |
Administration Considerations
- Maximum time between doses should not exceed 12 hours 1
- Gabapentin is not metabolized and does not induce hepatic enzymes 4
- Elimination half-life is approximately 5-9 hours, necessitating three divided doses per day 4
- Steady state is achieved rapidly 4
Adverse Effects
Common adverse effects include:
- Dizziness (most common)
- Somnolence
- Peripheral edema
- Gait disturbance 5
Clinical Pearls
- Slow titration improves tolerability
- Bioavailability decreases with increasing doses due to saturable absorption 5, 4
- No significant interactions with other antiepileptic drugs or oral contraceptives 4
- Gabapentin is not protein-bound and is excreted unchanged in urine 4
- Plasma clearance is linearly related to creatinine clearance 4
Comparison with Pregabalin
If considering alternatives, pregabalin offers:
- Higher bioavailability (>90%, dose-independent)
- Faster titration (days vs. weeks)
- Lower therapeutic dose (150-600 mg/day vs. 900-3600 mg/day)
- Twice daily dosing vs. three times daily for gabapentin 5
Starting with a low dose and gradually titrating upward minimizes adverse effects while achieving therapeutic benefit. For most adult patients without renal impairment, the 300 mg → 600 mg → 900 mg titration over three days provides the optimal balance of efficacy and tolerability.