Gabapentin Dosing and Patient Counseling
For patients starting gabapentin (Neurontin), begin with a low dose of 100-300 mg at bedtime or 300 mg once daily, then gradually titrate to an effective maintenance dose range of 900-3600 mg/day in divided doses. 1, 2
Initial Dosing Strategy
- For postherpetic neuralgia, initiate with 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, with subsequent titration as needed for pain relief 2
- For epilepsy in patients 12 years and older, start with 300 mg three times daily, with a recommended maintenance dose of 300-600 mg three times daily 2
- Slower titration is recommended for elderly or medically frail patients, with increases by 300 mg increments every 3-7 days as tolerated 1
- For neuropathic pain, treatment should be initiated at low dosages with gradual titration until pain relief, dose-limiting adverse effects, or the maximum dose of 3600 mg/day in 3 divided doses is reached 3
Dosage Adjustment in Special Populations
- Adjust dosage based on creatinine clearance in patients with renal impairment 1, 2
- For patients with creatinine clearance ≥60 mL/min: standard dosing (900-3600 mg/day) 2
- For patients with creatinine clearance 30-59 mL/min: 400-1400 mg/day in divided doses 2
- For patients with creatinine clearance 15-29 mL/min: 200-700 mg/day 2
- For patients with creatinine clearance <15 mL/min: 100-300 mg/day 2
- Elderly patients should start at lower doses and titrate more slowly due to potential decreased renal function 1, 2
Efficacy Considerations
- For neuropathic pain, an adequate trial of gabapentin can require 2 months or more to determine full efficacy 3
- In clinical studies for postherpetic neuralgia, efficacy was demonstrated over a range of doses from 1800 mg/day to 3600 mg/day, but additional benefit of using doses greater than 1800 mg/day was not demonstrated 2, 4
- The maximum single dose is generally 1200 mg, as part of the maximum daily dose of 3600 mg divided into three doses 3
Administration Guidelines
- Gabapentin can be taken with or without food 2
- The maximum time between doses should not exceed 12 hours 2
- If a patient divides a scored 600 mg or 800 mg tablet, they should take the unused half-tablet as the next dose; half-tablets not used within 28 days should be discarded 2
- If gabapentin dose is reduced, discontinued, or substituted with an alternative medication, this should be done gradually over a minimum of 1 week 2
Side Effects and Monitoring
- Common side effects include dizziness and somnolence, which are typically mild to moderate and often transient 1, 5
- Dizziness and somnolence are most common during initial titration and may not increase in frequency or worsen with titration to doses ≥1800 mg/day 5
- Peripheral edema may increase in incidence at doses ≥1800 mg/day 5
- Side effects can be reduced by starting with lower dosages and titrating cautiously 3
Patient Counseling Points
- Inform patients that efficacy for neuropathic pain may take several weeks to achieve optimal effect 1
- Advise patients that gabapentin has a favorable safety profile with minimal drug interactions 1
- Warn patients about potential dizziness and somnolence, especially when starting therapy or increasing doses 1, 5
- Instruct patients not to abruptly discontinue the medication 2
- Explain that the medication can be taken with or without food 2
- Advise patients to report any unusual changes in mood or behavior 2
Clinical Pearls
- Gabapentin's relative bioavailability may decrease slightly with increasing doses 6
- Studies suggest that 600 mg/day could be a safe and effective starting dose for patients with post-herpetic neuralgia, as starting with a minimal dose of 200 mg/day did not offer a better reduction of side effects 7
- For unexplained chronic cough, a therapeutic trial of gabapentin can be considered with dose escalation beginning at 300 mg once daily up to a maximum tolerable daily dose of 1800 mg in two divided doses 3