What is the appropriate dosage and prescription guidelines for gabapentin (Neurontin) scripts?

Gabapentin Prescription Guidelines

Gabapentin is not a controlled substance in most U.S. states and has no federal limit on the number of prescriptions that can be written, though prescribers should follow FDA-approved dosing guidelines and monitor for state-specific regulations as some states have recently classified it as a controlled substance. 1

Regulatory Status and Prescription Limits

• Gabapentin is not federally scheduled as a controlled substance by the DEA, meaning there are no federal restrictions on the number of scripts that can be written 1
• However, several states (including Kentucky, Michigan, Tennessee, Virginia, and West Virginia) have reclassified gabapentin as a Schedule V controlled substance, which may impose state-specific prescribing limitations 1
• Prescribers should verify their state's current classification before writing multiple prescriptions 1

FDA-Approved Dosing Parameters

Standard Adult Dosing

• Initial dosing: Start at 300 mg once daily on Day 1, increase to 600 mg/day (300 mg twice daily) on Day 2, then 900 mg/day (300 mg three times daily) on Day 3 1
• Maintenance dosing: 300-600 mg three times daily (900-1800 mg/day total) 1
• Maximum studied dose: Up to 3600 mg/day has been administered and well-tolerated, though doses above 1800 mg/day have not demonstrated additional benefit in clinical trials 1
• Dosing interval: Maximum time between doses should not exceed 12 hours 1

Guideline-Based Recommendations

• The National Comprehensive Cancer Network recommends starting at 100-300 mg at bedtime or 300 mg once daily, with typical effective maintenance doses of 900-3600 mg/day in divided doses 2
• For HIV-associated neuropathic pain, a typical adult regimen titrates to 2400 mg per day in divided doses 3
• Slower titration by 300 mg increments every 3-7 days is recommended for elderly or medically frail patients 2

Renal Dosing Adjustments (Critical)

Dose adjustment is mandatory for patients with renal impairment 1:

• CrCl ≥60 mL/min: 900-3600 mg/day in three divided doses 1
• CrCl 30-59 mL/min: 400-1400 mg/day in two divided doses 1
• CrCl 15-29 mL/min: 200-700 mg/day as single daily dose 1
• CrCl <15 mL/min: 100-300 mg/day as single daily dose 1
• Hemodialysis patients: Maintenance doses based on CrCl plus supplemental post-hemodialysis dose of 125-350 mg after each 4-hour dialysis session 1

Clinical Efficacy Evidence

Neuropathic Pain Conditions

• Postherpetic neuralgia: 32% of patients achieve substantial benefit (≥50% pain relief) at doses ≥1200 mg/day versus 17% with placebo (NNT 6.7) 4
• Diabetic neuropathy: 38% achieve substantial benefit at doses ≥1200 mg/day versus 21% with placebo (NNT 5.9) 4
• Efficacy for neuropathic pain may take several weeks to achieve optimal effect 2
• Treatment should start at 900 mg/day (titrated over 3 days) with additional titration to 1800 mg/day recommended for greater efficacy 5

Common Pitfalls to Avoid

• Do not write prescriptions without checking renal function - gabapentin is eliminated unchanged in urine and requires dose reduction even with moderate renal impairment (CrCl <60 mL/min) 1
• Do not abruptly discontinue - taper gradually over minimum of 1 week when reducing, discontinuing, or substituting with alternative medication 1
• Do not exceed 12-hour intervals between doses, as this reduces efficacy 1
• Verify state regulations before writing multiple prescriptions, as controlled substance status varies by state 1

Adverse Effects and Monitoring

• Common adverse events include dizziness (19%), somnolence (14%), peripheral edema (7%), and gait disturbance (14%) 4
• Adverse event withdrawals occur in 11% on gabapentin versus 8.2% on placebo (NNH 30) 4
• Side effects are typically mild to moderate and often transient, usually subsiding within approximately 10 days 5
• Serious adverse events occur at similar rates to placebo (3.2% vs 2.8%) 4

Special Populations

• Elderly patients: Start at lower doses and titrate more slowly with dose adjustments based on creatinine clearance, as elderly patients are more likely to have decreased renal function 1
• Pediatric patients (3-11 years): Starting dose 10-15 mg/kg/day in three divided doses; maintenance dose 25-50 mg/kg/day depending on age 1
• Patients <12 years with renal impairment: Use has not been studied 1