What is the recommended starting dose of gabapentin (Neurontin) for an adult patient with epilepsy or neuropathic pain, considering potential impaired renal function or elderly status?

Gabapentin Starting Dose

Start gabapentin at 300 mg once daily (at bedtime) on Day 1, increase to 300 mg twice daily on Day 2, then 300 mg three times daily (900 mg/day total) on Day 3. 1

Standard Titration Protocol

The FDA-approved dosing schedule provides the foundation for gabapentin initiation:

• Day 1: 300 mg as a single dose (preferably at bedtime to minimize initial dizziness) 1, 2
• Day 2: 600 mg/day (300 mg twice daily) 1
• Day 3: 900 mg/day (300 mg three times daily) 1

After reaching 900 mg/day, continue titrating upward by 300 mg increments every 3-7 days as tolerated until reaching the target therapeutic dose of 1800-3600 mg/day in three divided doses. 2, 1

Target Therapeutic Doses

For neuropathic pain (postherpetic neuralgia, diabetic neuropathy):

• Minimum effective dose: 1800 mg/day (600 mg three times daily) 2, 1
• Optimal dose range: 1800-3600 mg/day in three divided doses 2, 1, 3
• Maximum dose: 3600 mg/day (1200 mg three times daily) 1

For epilepsy (partial onset seizures):

• Maintenance dose: 900-1800 mg/day in three divided doses 1
• Maximum studied dose: 3600 mg/day 1

Special Population Adjustments

Elderly Patients

Start at 100-300 mg at bedtime and titrate more slowly (increase every 3-7 days or longer) due to increased fall risk from dizziness and higher likelihood of renal impairment. 2, 4

• Elderly patients rarely tolerate doses >1800 mg/day and often respond to lower doses than younger adults 2
• Always calculate creatinine clearance and adjust dose accordingly 1

Renal Impairment

Mandatory dose reduction based on creatinine clearance: 1

• CrCl ≥60 mL/min: Standard dosing (300 mg TID up to 1200 mg TID)
• CrCl 30-59 mL/min: 200-700 mg twice daily (start 200 mg BID)
• CrCl 15-29 mL/min: 100-300 mg once daily (start 100 mg QD)
• CrCl <15 mL/min: 100-300 mg once daily, reduced proportionally
• Hemodialysis: Maintenance dose based on CrCl plus supplemental 125-350 mg post-dialysis 1

Critical Dosing Principles

Three-times-daily dosing is mandatory for standard gabapentin due to saturable, nonlinear absorption pharmacokinetics—once or twice daily dosing is inadequate. 2 The maximum interval between doses should not exceed 12 hours. 1

Allow adequate trial duration: Efficacy develops gradually over several weeks. An adequate therapeutic trial requires 3-8 weeks for titration plus 2 weeks at maximum tolerated dose (potentially 2 months total). 2, 4

Doses above 1800 mg/day may not provide additional benefit in some patients, though individual response varies and some require the full 3600 mg/day for optimal pain relief. 4, 3

Common Pitfalls to Avoid

• Do not rush titration in elderly patients—this significantly increases fall risk from dizziness and sedation 2
• Do not use once or twice daily dosing with standard gabapentin (extended-release formulations differ) 2
• Do not discontinue abruptly—taper gradually over at least 1 week to avoid withdrawal symptoms 1
• Do not declare treatment failure prematurely—allow the full 2-month trial period before abandoning therapy 2
• Do not forget renal dose adjustment—gabapentin is eliminated renally and accumulates in renal impairment 1

Expected Outcomes

At therapeutic doses (1800-3600 mg/day), approximately 32-38% of patients achieve at least 50% pain reduction compared to 17-21% with placebo for neuropathic pain conditions. 2, 3 Common adverse effects include dizziness (19%), somnolence (14%), and peripheral edema (7%), which are typically mild to moderate and often transient. 2, 3