Duloxetine Safe, Effective, in Patients with Chronic Low Back Pain

BALTIMORE, Md.—Duloxetine 60 mg once daily was effective in reducing chronic low back pain compared with placebo, results of a phase III randomized, double-blind study have shown. Perception of improvement was also significantly greater among patients receiving duloxetine.

Vladimir Skljarevski, MD, of Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Ind., and colleagues randomized 401 adults with non-neuropathic chronic low back pain and a pain intensity of ≥4 on the Brief Pain Inventory (BPI), an 11-point numerical scale, with duloxetine 60 mg/day (n=198) or placebo (n=203). The effect of duloxetine, a serotonin and norepinephrine reuptake inhibitor, on reducing use of rescue analgesics was assessed, as was safety and tolerability.

The primary end point of the 12-week study was efficacy of duloxetine 60 mg once daily compared with placebo on reduction in pain severity as measured by the BPI (24-hour average pain ratings). Also assessed were BPI Severity and BPI Interference, response rates (either ≥30% or ≥50% based on BPI 24-hour average pain rating), Patient’s Global Impression of Improvement (PGI-I), and the Roland Morris Disability Questionnaire. Health outcomes measures were Short Form(SF)-36, EuroQoL-5D, Profile of Mood States-Brief Form, and Work Productivity and Activity Impairment. Safety and tolerability were assessed by discontinuations due to adverse events, treatment-emergent adverse events, vital signs, and laboratory tests.

Mean age of the patients was 54.9 years in the duloxetine group (59.6% female) and 53.4 years in the placebo group (63.1% female); all patients were predominantly Caucasian (>95%).

Patients treated with duloxetine reported a significantly greater reduction in BPI average pain compared with placebo at 3, 6, 9, and 12 weeks of treatment (P≤0.001). They also had a significantly greater improvement in BPI Severity and BPI Interference, 50% response rates, PGI-I, EuroQol-5D, and some SF-36 domains. A numerical improvement was also observed with duloxetine for the Roland Morris Disability Questionnaire, the Work Productivity Activity and Impairment, and 30% response rate.

Use of ibuprofen was significantly reduced (P=0.033) in the patients treated with duloxetine (12.6%) compared with those in the placebo group (20.7%). Those receiving duloxetine discontinued due to adverse events at a significantly higher rate, 15.2%, vs placebo, 5.4% (P≤0.01). The most common treatment-emergent adverse events were nausea and headache; nausea was reported by significantly more patients treated with duloxetine than with placebo (P<0.001).

Duloxetine is safe and fairly well tolerated, the investigators concluded during their presentation to those attending the American Pain Society’s 29th Annual Scientific Meeting.