A Randomized, Double‐Blind, Placebo‐Controlled Trial of Duloxetine for the Treatment of Pain in Patients with Multiple Sclerosis

BACKGROUND: Patients with multiple sclerosis (MS) often report neuropathic pain (NP-MS). The purpose of this study was to assess the efficacy and tolerability of duloxetine as treatment for NP-MS. METHODS: In this study, 239 adults with NP-MS (duloxetine = 118, placebo = 121) were randomized to duloxetine 60 mg (30 mg for 1 week, then 60 mg for 5 weeks) or placebo once daily for a 6-week acute therapy phase, followed by a 12-week open-label extension phase (duloxetine 30 to 120 mg/day). Eligible patients had MS for ≥ 1 year and a score ≥ 4 on daily average pain intensity (API) ratings for ≥ 4 of 7 days immediately before randomization. Patients rated API daily on an 11-point numeric scale (0 [no pain] to 10 [worst possible pain]) in an electronic diary. The primary efficacy measure, change in weekly API ratings, was analyzed longitudinally with a mixed-model repeated-measures analysis. Completion, reasons for discontinuation, and treatment-emergent adverse event incidence were compared by Fisher's exact test. RESULTS: Duloxetine-treated patients had statistically greater mean improvement in API vs. placebo at Week 6 (-1.83 vs. -1.07, P = 0.001). Treatment completion did not significantly differ between groups. Discontinuation due to adverse events was statistically greater for duloxetine vs. placebo (13.6% vs. 4.1%, P = 0.012). Decreased appetite was reported significantly more often by duloxetine-treated patients (5.9% vs. 0%, P = 0.007). CONCLUSIONS: This study found analgesic efficacy of duloxetine for NP-MS. Duloxetine is not approved for treatment of this condition. The duloxetine safety profile of this study was consistent with the known profile in other patient populations.