GABAPENTIN FOR THE TREATMENT OF POSTHERPETIC NEURALGIA - A RANDOMIZEDCONTROLLED TRIAL

Context.-Postherpetic neuralgia (PHN) is a syndrome of often intractab le neuropathic pain following herpes tester (shingles) that eludes eff ective treatment in many patients. Objective.-To determine the efficac y and safety of the anticonvulsant drug gabapentin in reducing PHN pai n. Design.-Multicenter, randomized, double-blind, placebo-controlled, parallel design, 8-week trial conducted from August 1996 through July 1997. Setting.-Sixteen US outpatient clinical centers. Participants.-A total of 229 subjects were randomized. Intervention.-A 4-week titrati on period to a maximum dosage of 3600 mg/d of gabapentin or matching p lacebo. Treatment was maintained for another 4 weeks at the maximum to lerated dose. Concomitant tricyclic antidepressants and/or narcotics w ere continued if therapy was stabilized prior to study entry and remai ned constant throughout the study. Main Outcome Measures.-The primary efficacy measure was change in the average daily pain score based on a n Ii-point Likert scale (0, no pain; 10, worst possible pain) from bas eline week to the final week of therapy, Secondary measures included a verage daily sleep scores, Short-Form McGill Pain Questionnaire (SF-MP Q), Subject Global Impression of Change and investigator-rated Clinica l Global Impression of Change, Short Form-36 (SF-36) Quality of Life Q uestionnaire, and Profile of Mood States (POMS). Safety measures inclu ded the frequency and severity of adverse events. Results.-One hundred thirteen patients received gabapentin, and 89 (78.8%) completed the s tudy; 116 received placebo, and 95 (81.9%) completed the study. By int ent-to-treat analysis, subjects receiving gabapentin had a statistical ly significant reduction in average daily pain score from 6.3 to 4.2 p oints compared with a change from 6.5 to 6.0 points in subjects random ized to receive placebo (P<.001). Secondary measures of pain as well a s changes in pain and sleep interference showed improvement with gabap entin (P<.001), Many measures within the SF-36 and POMS also significa ntly favored gabapentin (P less than or equal to.01). Somnolence, dizz iness, ataxia, peripheral edema, and infection were all more frequent in the gabapentin group, but withdrawals were comparable in the 2 grou ps (15 [13.3%] in the gabapentin group vs 11 [9.5%] in the placebo gro up). Conclusions.-Gabapentin is effective in the treatment of pain and sleep interference associated with PHN. Mood and quality of life also improve with gabapentin therapy.