Once-Daily Gastroretentive Gabapentin Improves PHN Pain and Quality of Life

HONOLULU, HI — In patients with postherpetic neuralgia (PHN), once-daily gabapentin 1,800mg improved all pain scores, as well as sleep and enjoyment of life interference scales, reported Misha Backonja, MD, from Lifetree Clinical Research, Salt Lake City, UT, and colleagues at the American Pain Society’s 31st Annual Scientific Meeting.

Dr. Backonja and colleagues conducted an analysis to investigate the effect of once-daily gabapentin on pain characteristics using the Brief Pain Inventory (BPI) instrument in two, Phase 3, 11-week, double-blind, randomized placebo-controlled studies (n=712; mean age 66.1 years; baseline BPI current pain mean of 5.9). The BPI scale characterized pain with five pain scores (worst, least and average pain in previous 24 hours, present pain, and percent relief) and seven interference scores (general activity, mood, walking ability, normal work, relationship, sleep, and enjoyment of life). 

Patients had one week of baseline observation, two weeks of titration to once-daily gabapentin 1,800mg or matched placebo (taken with evening meal), followed by eight weeks of stable dosing. The BPI questionnaire was administered at baseline and at Week 10. Last observation carried forward (LOCF) methodology was utilized to input all missing data.

Study results showed that all five pain scores improved by Week 10 in patients treated with once daily gabapentin (P=0.046–0.002). Of the seven interference scales, sleep and enjoyment of life were significantly improved (P<0.05); mood was borderline improved (P=0.054); and walking ability, work, relationship, and general activity were not significantly improved. Overall, the interference scales saw modest improvement (P=0.059).

Once-daily gabapentin was generally well tolerated. Dizziness (10.9% vs. 2.2% for placebo) and somnolence (4.5% vs. 2.7% for placebo) were the most common adverse events seen in the gabapentin treatment group.  Dr. Backonja concluded that in patients with PHN, gabapentin improved all pain scores and improved quality of life with minimal adverse effects.