Efficacy and safety of duloxetine in patients with chronic low back pain.

METHODS

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).

BACKGROUND

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.

CONCLUSIONS

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