Randomized double-blind study comparing the efficacy of gabapentin with amitriptyline on diabetic peripheral neuropathy pain

Background: Reports of gabapentin use in diabetic peripheral neuropathy pain stimulate a need for controlled trials to determine its comparative efficacy to the therapeutic standard of amitriptyline hydrochloride. Objective: To determine the efficacy of gabapentin compared with amitriptyline in treating diabetic peripheral neuropathy pain. Design: Prospective, randomized, double-blind, double-dummy, crossover study. Setting: Veterans Affairs San Diego Healthcare System, Ambulatory Care Clinic. Patients: Twenty-eight veterans were referred by their primary care providers. Two patients withdrew before randomization because of no neuropathic pain after washout; a third withdrew for unexpected surgery that required analgesics. Three patients withdrew because of adverse effects and 1 for protocol violation. Interventions: Patients with stable glycemic control and neuropathic gain randomized to 6 weeks of therapy with gabapentin, 900 to 1800 mg/d, or amitriptyline hydrochloride; 25 to 75 mg/d, with a 1-week washout before crossover. Main Outcome Measures: Pain relief measured by pain scale with verbal descriptors and global pain score assessment at treatment end. Results: Participants and investigators were blinded throughout. Mean dosages were of gabapentin, 1565 mg/d, and of amitriptyline hydrochloride, 59 mg/d. Sixty-five percent of patients reached maximum dose with gabapentin and 54% with amitriptyline. Mean score diary analysis showed pain relief with gabapentin and amitriptyline was not significantly different (P =.26). Global data were obtained from 21 of 25; enrolled patients who completed the study. Moderate or greater pain relief was experienced in 11 (52%) of 21 patients with gabapentin and 14 (67%) of 21 patients with amitriptyline. There were no significant period or carry-over effects (P=.35). Conclusions: Although both drugs provide pain relief, mean pain score and global pain score data indicate no significant difference between gabapentin and amitriptyline. Gabapentin may be an alternative for treating diabetic peripheral neuropathy pain, yet does not appear to offer considerable advantage over amitriptyline and is more expensive. Larger trials are necessary to define gabapentin's place in treating diabetic peripheral neuropathy pain.