What is the maximum dose of gabapentin (Neurontin) per day?

Maximum Dose of Gabapentin

The maximum dose of gabapentin is 3600 mg per day, typically divided into three doses. 1, 2, 3

Dosing Guidelines for Gabapentin

Standard Maximum Dosing

• The FDA-approved maximum daily dose of gabapentin is 3600 mg/day, divided into three doses 1
• For neuropathic pain, the effective dose range is typically between 1800-3600 mg/day 3
• In controlled studies, the effective gabapentin dose for pain is usually between 900 mg/day and 3600 mg/day in two to three divided doses 3

Dosing Schedule

• Gabapentin should be administered three times daily with the maximum time between doses not exceeding 12 hours 1
• The maximum single dose is generally 1200 mg, as part of the maximum daily dose of 3600 mg 2
• For postherpetic neuralgia, although efficacy was demonstrated across doses from 1800-3600 mg/day, additional benefit of using doses greater than 1800 mg/day was not demonstrated in clinical studies 1

Dose Titration

• Treatment should be initiated with a low starting dose (100-300 mg) and gradually titrated to minimize side effects 2, 3
• Initial dosing typically starts at 300 mg on day 1,600 mg/day (300 mg twice daily) on day 2, and 900 mg/day (300 mg three times daily) on day 3 1
• Dose can subsequently be titrated up as needed for pain relief to the maximum dose 3
• Dose escalation should continue until benefit occurs or side effects begin to appear 3

Special Populations

Renal Impairment

• Dosage adjustment is required in patients with compromised renal function 1
• For patients with creatinine clearance 30-59 mL/min: maximum 1400 mg/day 1
• For patients with creatinine clearance 15-29 mL/min: maximum 700 mg/day 1
• For patients with creatinine clearance <15 mL/min: maximum 300 mg/day 1

Elderly Patients

• Lower doses may be more appropriate in older adults due to potential for decreased renal function 3, 1
• The effective dose in older adults may be lower than the standard ranges due to increased sensitivity to side effects 3
• Care should be taken in dose selection, and dose should be adjusted based on creatinine clearance values in elderly patients 1

Efficacy and Safety Considerations

• In clinical trials, approximately 38% of patients with painful diabetic neuropathy achieved at least 50% pain relief with gabapentin at doses of 1200 mg daily or greater compared to 21% with placebo 4
• Adverse events are more common with gabapentin (63%) than with placebo (49%), with the most common side effects being dizziness (19%), somnolence (14%), peripheral edema (7%), and gait disturbance (14%) 4
• Higher doses may not always provide additional benefit but can increase the risk of side effects 1, 4

Clinical Pearls

• An adequate trial of gabapentin for pain can require 2 months or more to determine full efficacy 2
• If gabapentin needs to be discontinued, it should be done gradually over a minimum of 1 week to avoid withdrawal symptoms 1
• For unexplained chronic cough, the maximum tolerable daily dose is typically lower at 1800 mg in two divided doses 2

Remember that while 3600 mg/day is the maximum approved dose, the optimal dose should be determined by balancing efficacy with tolerability, and many patients may achieve adequate pain relief at lower doses.