Recommended Gabapentin Dosing for Postherpetic Neuralgia
For postherpetic neuralgia, gabapentin should be initiated at 300 mg on day 1, increased to 600 mg/day (300 mg twice daily) on day 2, and further increased to 900 mg/day (300 mg three times daily) on day 3, with subsequent titration up to 1800 mg/day (600 mg three times daily) as needed for pain relief. 1
Initial Dosing and Titration
Gabapentin is recommended as a first-line oral pharmacological treatment for postherpetic neuralgia with a structured titration schedule:
- Day 1: Single 300 mg dose
- Day 2: 600 mg/day (300 mg twice daily)
- Day 3: 900 mg/day (300 mg three times daily)
- Subsequently: Titrate up as needed for pain relief to 1800 mg/day 1
This gradual titration helps minimize adverse effects while establishing therapeutic benefit. The FDA-approved dosing indicates that efficacy has been demonstrated over a range from 1800 mg/day to 3600 mg/day, but importantly, additional benefit of using doses greater than 1800 mg/day was not demonstrated in clinical studies 1.
Efficacy and Evidence
Gabapentin has proven efficacy for postherpetic neuralgia:
- In randomized controlled trials, gabapentin significantly reduced pain scores compared to placebo (from 6.3 to 4.2 points vs. 6.5 to 6.0 points with placebo) 2
- The number needed to treat (NNT) for gabapentin in postherpetic neuralgia is 4.39, indicating good clinical efficacy 3
- A typical adult regimen will titrate to 2400 mg per day in divided doses 3
Dosing Frequency
- Gabapentin should be administered three times daily 1
- The maximum time between doses should not exceed 12 hours to maintain therapeutic levels 1
- Once-daily gastroretentive formulations are available but were not included in the primary guidelines for postherpetic neuralgia 4
Dosage Adjustment in Renal Impairment
Renal function significantly impacts gabapentin dosing, requiring adjustment based on creatinine clearance:
| Creatinine Clearance (mL/min) | Total Daily Dose Range (mg/day) | Dose Regimen |
|---|---|---|
| ≥60 | 900-3600 | 300-1200 mg TID |
| >30-59 | 400-1400 | 200-700 mg BID |
| >15-29 | 200-700 | 200-700 mg QD |
| ≤15 | 100-300 | 100-300 mg QD |
Patients on hemodialysis should receive a supplemental post-hemodialysis dose after each 4 hours of hemodialysis 1.
Elderly Patients
Elderly patients require special consideration:
- More likely to have decreased renal function
- Dose should be adjusted based on creatinine clearance values
- Start at the lower end of the dosing range and titrate more slowly 1
Common Adverse Effects
Be aware of common adverse effects with gabapentin:
- Somnolence (reported by 80% of patients) 3
- Dizziness
- Ataxia
- Peripheral edema (occurs in approximately 7% of patients) 5
- Infection 2
Duration of Treatment
- Efficacy assessment should occur after 3-8 weeks of titration plus 2 weeks at maximum dose 5
- If discontinuing gabapentin, taper gradually over at least 1 week to avoid withdrawal symptoms 5
Alternative Treatments
If patients have an inadequate response to gabapentin, consider:
- Pregabalin (may be more effective for some patients with postherpetic neuralgia) 3
- Tricyclic antidepressants 3
- Serotonin-norepinephrine reuptake inhibitors 3
- Topical capsaicin (8% dermal patch or cream) 3
Important Clinical Considerations
- Doses above 1800 mg/day have diminishing returns with increased risk of adverse effects 5
- Gabapentin improves not only pain but also sleep scores in patients with postherpetic neuralgia 3, 2
- Mood and quality of life measures also improve with gabapentin therapy 2
- Avoid combining with other sedative medications when possible to reduce risk of adverse effects 5
Remember that while gabapentin is effective for treating established postherpetic neuralgia, it has not been shown to be effective for preventing postherpetic neuralgia when given during acute herpes zoster 6.