Gabapentin Dosing for Postherpetic Neuralgia in Shingles
For postherpetic neuralgia, gabapentin should be initiated 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, with subsequent titration up to 1800 mg/day as needed for pain relief. 1
Initial Dosing and Titration Schedule
- Start with 300 mg on day 1 as a single dose 1
- Increase to 600 mg/day (300 mg twice daily) on day 2 1
- Increase to 900 mg/day (300 mg three times daily) on day 3 1
- Subsequently titrate up as needed for pain relief to a maximum of 1800 mg/day (600 mg three times daily) 1, 2
Effective Dose Range
- Clinical efficacy has been demonstrated across a dose range from 1800 mg/day to 3600 mg/day 1
- However, additional benefit of using doses greater than 1800 mg/day has not been demonstrated in clinical studies 1, 2
- The maximum time between doses should not exceed 12 hours to maintain therapeutic effect 1
Dosage Adjustment in Special Populations
Renal Impairment
- For patients with creatinine clearance 30-59 mL/min: 400-1400 mg/day in divided doses 1
- For patients with creatinine clearance 15-29 mL/min: 200-700 mg/day in divided doses 1
- For patients with creatinine clearance <15 mL/min: 100-300 mg/day as a single daily dose 1
Elderly Patients
- Start with lower doses and titrate more slowly due to decreased renal function 1, 3
- Consider starting at 100-300 mg at bedtime and increase gradually 3, 2
Efficacy and Evidence
- Gabapentin has demonstrated efficacy for postherpetic neuralgia with a number needed to treat (NNT) of 4.39 3
- In randomized controlled trials, gabapentin significantly reduced pain from 6.3 to 4.2 points compared to minimal change with placebo (6.5 to 6.0) 4
- Gabapentin also improves sleep interference and quality of life measures in patients with postherpetic neuralgia 4
Common Side Effects and Management
- Most common adverse effects include somnolence, dizziness, ataxia, and peripheral edema 4
- Side effects can be minimized by:
Alternative Formulations
- Once-daily gastroretentive formulations are available that may improve adherence and reduce side effects through gradual release 6
- These formulations may have a lower incidence of dizziness and somnolence compared to three-times-daily dosing 6
Treatment Duration and Monitoring
- An adequate trial of gabapentin treatment may require 2 months or more 3
- Regular assessment of pain relief, functional improvement, and side effects should guide continued therapy 2
- If inadequate response after 8 weeks at maximum tolerated dose, consider alternative or adjunctive therapy 3, 7
Alternative Options if Gabapentin Fails
- Pregabalin may be considered if patients have inadequate response to gabapentin 3
- Tricyclic antidepressants show excellent efficacy (NNT = 2.64) and may be used as alternatives 3
- Topical lidocaine patches (5%) provide excellent efficacy (NNT = 2) with minimal systemic effects 2
Gabapentin remains a first-line treatment for postherpetic neuralgia with established efficacy and a manageable side effect profile when properly titrated.