A 3-year, open-label, flexible-dosing study of milnacipran for the treatment of fibromyalgia

Abstract

Objectives: To evaluate the effects of long-term milnacipran treatment in fibromyalgia patients.

Methods: Patients completing a previous milnacipran study were eligible to participate in this long-term (up to 3.25 y), open-label study. After washout, dose escalation, and 8 weeks of stable-dose treatment (100 mg/d), patients received flexible doses of milnacipran (50 to 200 mg/d) for the remainder of the study. Safety evaluations included adverse events and vital signs. Clinical measures included weekly recall pain (visual analog scale [VAS]), Patient Global Disease Status (PGDS), and the Short Form-36 Health Survey (SF-36, including the Physical Component Summary [PCS] and Mental Component Summary scores). Cohort analyses were conducted to assess the effects of milnacipran over varying periods of time.

Results: Of 1227 patients entering the study, 585 (47.7%) were classified as completers, including 379 (30.9%) patients who were currently enrolled when the study was administratively terminated. Mean duration of treatment was 19 months, with 206 patients reaching the final visit and receiving 36 to 38 months of study treatment. The percentage of patients with ≥1 treatment-emergent adverse event was 88.3%, with nausea (25.9%) and headache (13.4%) being the most common events. Discontinuations due to adverse events occurred in 20.9% of patients. Potentially clinically significant increases in blood pressure or heart rate occurred in ≤1.1% of patients. Mean improvement from baseline in weekly recall VAS pain was 17.6; improvements in global status (PGDS) and physical functioning (SF-36 PCS) were also observed. In all patient cohorts, these improvements were observed by month 3 and remained relatively constant over time. At final study visit in the 3-year cohort, 70.3% of patients rated their overall fibromyalgia as "much improved" or "very much improved."

Discussion: No new safety concerns were identified in this long-term study. Sustained symptom improvements were found in fibromyalgia patients who received up to 3.25 years of milnacipran treatment.