What is the recommended gabapentin dosing regimen for adults with neuropathic pain or post‑herpetic neuralgia, including initial dose, titration schedule, maximum dose, and dose adjustments for elderly patients and for moderate (creatinine clearance 30–60 mL/min) or severe (creatinine clearance <30 mL/min) renal impairment, and what are the pediatric dosing guidelines for epilepsy?

Gabapentin Dosing for Neuropathic Pain and Epilepsy

Start gabapentin at 300 mg on day 1, increase to 600 mg/day (300 mg twice daily) on day 2, then to 900 mg/day (300 mg three times daily) on day 3, and titrate upward by 300 mg every 3–7 days until reaching the minimum effective dose of 1800 mg/day (600 mg three times daily), with a maximum of 3600 mg/day (1200 mg three times daily) for adults with neuropathic pain. 1, 2

Standard Adult Dosing for Neuropathic Pain

Initial Titration Schedule

• Day 1: 300 mg once daily 1
• Day 2: 600 mg/day (300 mg twice daily) 1
• Day 3: 900 mg/day (300 mg three times daily) 1
• Days 4+: Increase by 300 mg increments every 3–7 days as tolerated 2, 3

Target Therapeutic Dose Range

• Minimum effective dose: 1800 mg/day (600 mg three times daily) 2, 1, 4
• Standard therapeutic range: 1800–3600 mg/day in three divided doses 2, 3
• Maximum dose: 3600 mg/day (1200 mg three times daily) 2, 1

The evidence shows that 32–38% of patients achieve at least 50% pain reduction at therapeutic doses (1800–3600 mg/day) compared to 17–21% with placebo in postherpetic neuralgia and painful diabetic neuropathy 5. The FDA label notes that while efficacy was demonstrated across the 1800–3600 mg/day range, additional benefit above 1800 mg/day was not consistently demonstrated in clinical trials 1.

Critical Dosing Requirement: Three Times Daily Administration

• Gabapentin MUST be administered three times daily due to nonlinear, saturable absorption pharmacokinetics 2, 3, 1
• The maximum interval between doses should not exceed 12 hours 1
• Once-daily or twice-daily dosing leads to subtherapeutic levels and treatment failure 2, 3

Duration of Adequate Trial

• Allow 3–8 weeks for titration PLUS 2 weeks at maximum tolerated dose before declaring treatment failure 2, 3
• An adequate therapeutic trial may require 2 months or more, as efficacy develops gradually over several weeks 2, 4
• Do not discontinue prematurely—pain relief is gradual, not immediate 2

Elderly Patient Dosing

Modified Titration for Geriatric Patients

• Start at 100–200 mg/day (significantly lower than standard adult dosing) 2
• Titrate more slowly: increase by 100–300 mg every 3–7 days (use the longer 5–7 day interval) 2, 3
• The effective dose in older adults may be below the standard adult range 2
• Elderly patients experience higher rates of adverse effects: dizziness (19%), somnolence (14%), peripheral edema (7%), and gait disturbance (9%) 2

Critical Pitfall in Elderly Patients

• Do not rush titration—rapid dose escalation increases fall risk from dizziness 2, 3
• Use every 5–7 day intervals rather than every 3 days to minimize adverse effects 3

Renal Impairment Dose Adjustments

Dose reduction is mandatory based on creatinine clearance (CLcr), as gabapentin is eliminated primarily by renal excretion 2, 1. Calculate CLcr using the Cockcroft-Gault equation before initiating therapy 1:

CLcr (mL/min) = [(140 - age) × weight in kg] / (72 × serum creatinine in mg/dL)
Multiply by 0.85 for females 1

Renal Dosing Table

Creatinine Clearance	Total Daily Dose Range	Dosing Frequency
≥60 mL/min	900–3600 mg/day	Three times daily (300–1200 mg TID) [1]
30–59 mL/min	400–1400 mg/day	Twice daily (200–700 mg BID) [1]
15–29 mL/min	200–700 mg/day	Once daily (200–700 mg QD) [1]
<15 mL/min	100–300 mg/day	Once daily (100–300 mg QD) [1]

Hemodialysis Patients

• Administer maintenance doses based on CLcr as above 1
• Add a supplemental post-hemodialysis dose after each 4-hour dialysis session: 125–350 mg depending on maintenance dose 1
• For CLcr <15 mL/min, reduce daily dose in proportion to CLcr (e.g., patients with CLcr 7.5 mL/min receive one-half the dose for CLcr 15 mL/min) 1

Special Consideration for Elderly with Renal Impairment

• Elderly patients often have age-related decline in renal function masked by normal serum creatinine due to reduced muscle mass 6
• Always calculate CLcr—do not assume normal renal function based on serum creatinine alone 6
• The Cockcroft-Gault equation or CKD-EPI creatinine-cystatin C equation should be used 6

Pediatric Dosing for Epilepsy (Ages 3–11 Years)

Initial Dosing

• Starting dose range: 10–15 mg/kg/day in three divided doses 1
• Titrate upward over approximately 3 days to reach maintenance dose 1

Maintenance Dosing by Age

• Ages 3–4 years: 40 mg/kg/day in three divided doses 1
• Ages 5–11 years: 25–35 mg/kg/day in three divided doses 1
• Dosages up to 50 mg/kg/day have been well tolerated in long-term studies 1

Administration Details

• Maximum interval between doses: 12 hours 1
• May use oral solution, capsules, tablets, or combinations 1

Adolescents ≥12 Years

• Use adult dosing: 300 mg three times daily as starting dose 1
• Maintenance dose: 300–600 mg three times daily 1
• Maximum: 2400 mg/day (well tolerated in long-term studies); doses up to 3600 mg/day have been used short-term 1

Common Adverse Effects and Management

Most Frequent Side Effects

• Dizziness (19%), somnolence (14%), peripheral edema (7%), and gait disturbance (9%) 5, 7
• Adverse events are typically mild to moderate and usually subside within approximately 10 days from initiation 4, 7
• Adverse event withdrawals occur in 11% with gabapentin versus 8.2% with placebo 5

Mitigation Strategies

• Start with lower doses and implement slow titration to minimize peak-related side effects 2, 4
• Consider divided dosing (three times daily is mandatory anyway) 2
• For intolerable side effects, reduce dose rather than discontinuing 6

Critical Pitfalls to Avoid

1. Do not use once or twice daily dosing—three times daily is essential due to saturable absorption 2, 3, 1

2. Do not rush titration in elderly patients—increases fall risk from dizziness; use 5–7 day intervals 2, 3

3. Do not declare treatment failure before completing the full 2-month trial at therapeutic doses, as efficacy develops gradually 2, 3

4. Do not discontinue abruptly—taper gradually over at least 1 week to avoid withdrawal symptoms 2, 3

5. Do not use standard doses in renal impairment—mandatory dose reduction based on CLcr 2, 1

6. Do not assume normal renal function in elderly patients based on serum creatinine alone—always calculate CLcr 6

Discontinuation Protocol

• Taper gradually over a minimum of 1 week to avoid withdrawal symptoms 2, 3
• For patients on 300 mg/day, extend each tapering step to 2 weeks if withdrawal symptoms occur 6
• Never stop gabapentin abruptly 3