Data from a new study suggest that Cymbalta (duloxetine HCl) 60-120 mg once daily significantly reduced chronic low back pain, as measured by the Brief Pain Inventory (BPI) 24-hour average pain score, compared with placebo. Results from the double-blind, 13-week, placebo-controlled study of 236 patients were presented at the annual congress of the European Federation of Neurological Societies (EFNS) in Madrid, Spain.

Duloxetine-treated patients reported significantly greater reduction in pain scores than placebo-treated patients. Thirty-one percent of duloxetine-treated patients experienced a 50 per cent reduction in pain, compared with 19 per cent of placebo-treated patients, as measured by an 11-point Likert pain scale. Physicians consider a pain reduction of at least 30 per cent as clinically significant.

Treatment with duloxetine also was associated with improved patient outcomes as measured by the Patient Global Impressions of Improvement (PGI-I), and physical functioning as measured by the Roland Morris Disability Questionnaire (RMDQ-24).

Significantly more patients in the duloxetine group discontinued because of adverse events. In this study, the most common adverse events (those occurring in more than 5 per cent of patients in the duloxetine group) were nausea, dry mouth, fatigue, diarrhoea, excessive sweating (hyperhidrosis), dizziness and constipation. Adverse events were similar to those seen in previous duloxetine studies in other disease states.

"Chronic low back pain can have a significant impact on a person's ability to do the things they enjoy," said Vladimir Skljarevski, lead study author and a neurologist and medical fellow at Lilly Research Laboratories. "This research may offer hope to those dealing with this debilitating condition."

Data from a separate duloxetine chronic low back pain study were presented on August 21 at the 12th World Congress of Pain in Glasgow, Scotland. At study endpoint, duloxetine did not significantly differ from placebo on the primary measure of weekly mean 24-hour average pain score. However, patients taking duloxetine 60 mg once daily showed significant pain reductions compared with placebo from week three through week 11 of the 13-week trial. This was the first study designed to assess the effect of duloxetine on the reduction of chronic low back pain compared with placebo.

In the 13-week, double-blind, randomized, placebo-controlled study (n=404), patients taking duloxetine 60 mg once daily experienced statistically significant improvements in several secondary outcome measures compared with placebo. Patients taking duloxetine 60 mg once daily also experienced a statistically significant improvement in patient outcomes as measured by the PGI-I and physical functioning as measured by the RMDQ-24. In this study, the most common adverse events (those occurring in more than 5 percent of patients in the duloxetine group) were nausea, insomnia, dry mouth, constipation, headache, diarrhoea, dizziness, somnolence (drowsiness) and fatigue.

Serotonin and norepinephrine in the brain and spinal cord are believed to both mediate core mood symptoms and help regulate the perception of pain. Based on preclinical studies, Cymbalta is a balanced and potent reuptake inhibitor of serotonin and norepinephrine that is believed to potentiate the activity of these chemicals in the central nervous system (brain and spinal cord). While the mechanism of action of Cymbalta is not fully known, scientists believe its effects on depression and anxiety symptoms, as well as its effect on pain perception, may be due to increasing the activity of serotonin and norepinephrine in the central nervous system.

Cymbalta is approved in the United States for the acute and maintenance treatment of major depressive disorder, the acute treatment of generalized anxiety disorder, and the management of fibromyalgia and diabetic peripheral neuropathic pain in adults age 18 years and older. Cymbalta is not approved for use in paediatric patients.

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