The FDA has approved duloxetine (Cymbalta) to treat chronic musculoskeletal pain, including discomfort from osteoarthritis and chronic low back pain (FDA Press Release 2010 Nov 4). Several recent randomized trials have evaluated the efficacy of duloxetine for pain reduction in patients with chronic low back pain, but the trials were of short duration (12-13 weeks) and had high dropout rates. One trial randomized 401 adult patients to duloxetine 60 mg vs. placebo once daily for 12 weeks. Duloxetine was associated with significant improvement, with ? 50% pain reduction in 48.7% vs. 34.7% (p = 0.006, NNT 8) (J Pain 2010 Dec;11(12):1282). Another trial with 236 patients randomized to individually adjusted doses of duloxetine (60-120 mg) vs. placebo showed a nonsignificant trend toward greater pain reduction with duloxetine (? 50% pain reduction in 38.5% vs. 27%, p = 0.09) (Spine (Phila Pa 1976) 2010 Jun 1;35(13):E578). In a third trial, 404 patients received duloxetine at 1 of 3 doses (20 mg, 60 mg or 120 mg) vs. placebo. There was no significant pain reduction for either the 20 mg or 60 mg duloxetine doses. At 120 mg (maximal approved dose), duloxetine was associated with more patients achieving ? 30% pain reduction (57.8% vs. 43.4%, p = 0.033, NNT 7), but there was not a significant difference in ? 50% pain reduction (Eur J Neurol 2009 Sep;16(9):1041). In each trial, duloxetine was associated with increased risk of discontinuation due to adverse effects (NNH 6-12). All of the trials had high dropout rates (23%-34%) (level 2 [mid-level] evidence).
For more information, see the Duloxetine and Chronic low back pain topics in DynaMed.