Study design: This was a randomized, double-blind, placebo-controlled clinical trial.

Objective: To assess the efficacy and safety of duloxetine in the treatment of chronic low back pain (CLBP).

Summary of background data: Imbalance of serotonin and norepinephrine within modulatory pain pathways has been implicated in the development and maintenance of chronic pain. Duloxetine, a selective reuptake inhibitor of serotonin and norepinephrine, has demonstrated clinical efficacy in 3 distinct chronic pain conditions: diabetic peripheral neuropathic pain, fibromyalgia, and chronic pain because of osteoarthritis.

Methods: In this randomized double-blind trial, adult nondepressed patients with a non-neuropathic CLBP and a weekly mean of the 24-hour average pain score>or=4 at baseline (0-10 scale) were treated with either duloxetine or placebo for 13 weeks. The dose of duloxetine during first 7 weeks was 60 mg once daily. At week 7, patients reporting<30% pain reduction had their dose increased to 120 mg. The primary outcome measure was the Brief Pain Inventory (BPI) 24-hour average pain rating. Secondary measures included Roland-Morris Disability Questionnaire-24; Patient's Global Impressions of Improvement; Clinical Global Impressions-Severity (CGI-S); BPI-Severity and -Interference (BPI-I); and weekly means of the 24-hour average pain, night pain, and worst pain scores from patient diaries. Quality-of-life, safety, and tolerability outcomes were also assessed.

Results: Compared with placebo-treated patients (least-squares mean change of -1.50), patients on duloxetine (least-squares mean change of -2.32) had a significantly greater reduction in the BPI 24-hour average pain from baseline to endpoint (P=0.004 at week 13). Additionally, the duloxetine group significantly improved on Patient's Global Impressions of Improvement; Roland-Morris Disability Questionnaire-24; BPI-Severity and average BPI-Interference; weekly mean of the 24-hour average pain, night pain, and worst pain. Significantly more patients in the duloxetine group (13.9%) compared with placebo (5.8%) discontinued because of adverse events (P=0.047). The most common treatment-emergent adverse events in the duloxetine group included nausea, dry mouth, fatigue, diarrhea, hyperhidrosis, dizziness, and constipation.

Conclusion: Duloxetine significantly reduced pain and improved functioning in patients with CLBP. The safety and tolerability were similar to those reported in earlier studies.