Dose-response study of the analgesic effect of lanepitant in patients withpainful diabetic neuropathy

Lanepitant is effective in the formalin analgesic model suggesting efficacy in painful neuropathy. This study was designed to evaluate the dose-respon se effect of lanepitant in patients with daily moderate to severe, bilatera l, distal neuropathic pain. After a 1- to 3-week lead-in period, patients w ere randomly allocated to double-blind, parallel treatment with lanepitant 50 mg daily (n = 27), 100 mgr daily (n = 27), 200 mg twice daily (n = 13), or placebo (n = 26) over 8 weeks. Patients reported average daytime pain an d average nighttime pain intensity. Plasma concentrations and amount of adj unctive analgesic medication were obtained at all visits after baseline. Pa tient global evaluation and clinician global impression were obtained at we eks 3 and 8. Safety was assessed by adverse events, vital signs, laboratory analytes, and electrocardiogram. No dosage of lanepitant differed signific antly from placebo. Efficacy did not increase with lanepitant dosage, and h igher plasma concentrations were no more effective than lower plasma concen trations. The adverse event diarrhea was more Frequent for lanepitant-treat ed patients. Although well tolerated, lanepitant was ineffective in relievi ng pain of diabetic neuropathy.