Gabapentin and Venlafaxine for the Treatment of Painful Diabetic Neuropathy

OBJECTIVE: To evaluate the safety and efficacy of gabapentin and venlafaxine in the treatment of painful diabetic neuropathy in patients whose pain did not improve with gabapentin monotherapy. METHODS: (1) A randomized, double-blind, placebo-controlled, 8-week clinical trial comparing gabapentin versus placebo to define a patient population whose pain did not improve with monotherapy; (2) a second 8-week trial comparing gabapentin plus venlafaxine with gabapentin plus placebo; (3) a third uncontrolled 8-week trial of patients who did not improve on gabapentin monotherapy and then received venlafaxine in addition to gabapentin. RESULTS: (1) Gabapentin-treated patients showed statistically significant improvement in pain reduction as well as improvement in quality of life and mood disturbance when compared with placebo-treated patients; (2) patients who received gabapentin plus venlafaxine showed significant improvement in pain reduction, mood disturbance, and quality of life when compared with patients treated with gabapentin plus placebo; (3) patients who received gabapentin plus venlafaxine showed significant improvement in pain reduction, mood disturbance, and quality of life. CONCLUSIONS: (1) Gabapentin is efficacious in the treatment of painful diabetic neuropathy; (2) and (3) in patients who do not respond to gabapentin monotherapy, the addition of venlafaxine is also efficacious.