Clinical Experience With Desvenlafaxine in Treatment of Patients With Fibromyalgia Syndrome.

Two multicenter, randomized, placebo-controlled, adaptive-design trials of desvenlafaxine for fibromyalgia syndrome (FMS) were conducted. In study 1, male and female patients were randomized to a 27-week treatment with placebo or desvenlafaxine 50, 100, 200, or 400 mg/d. In study 2, female patients were randomized to an 8-week treatment with placebo, desvenlafaxine 200 mg/d, or pregabalin 450 mg/d after a placebo run-in. The primary efficacy end point was change from baseline in numeric rating scale (NRS) pain score. Protocol-specified interim analyses were planned after 12 (study 1) and 8 (study 2) weeks of treatment. Safety data were collected. In all, 697 patients were randomly assigned to treatment in study 1. At the interim analysis (n = 346), none of the desvenlafaxine doses met the efficacy criteria (mean [SE] advantage over placebo, -0.21 [0.36] to 0.04 [0.35]), and the study was terminated. Study 2 was stopped for business reasons before the planned interim analysis. NRS scores in week 8 were -1.98 (0.37), -1.60 (0.37), and -1.70 (0.38) for placebo (n = 26), desvenlafaxine 250 mg/d (n = 24), and pregabalin 450 mg/d (n = 21), respectively; neither active treatment differed significantly from placebo. Desvenlafaxine was generally safe and well tolerated. Efficacy of desvenlafaxine for pain associated with FMS was not demonstrated.