Duloxetine: A Balanced and Selective Norepinephrine and Serotonin-Reuptake Inhibitor

Anders D. Westanmo; Jon Gayken; Robert Haight


Am J Health Syst Pharm. 2005;62(23):2481-2490. 

In This Article

Diabetic Peripheral Neuropathic Pain

The Centers for Disease Control and Prevention has estimated that one in three people born in the United States in 2000 will develop diabetes.[52] Of the people who have diabetes over 10 years, 20% will develop chronic neuropathic pain and over 30% will develop sensory neuropathy.[53,54]

Neuropathic pain can stem from many potential pathologic processes.[55,56] Over the past 10 years a great deal has been learned about the causes of neuropathic pain, and there are drugs with FDA-approved indications for trigeminal neuralgia (e.g., carbamazepine) and postherpetic neuropathy (e.g., gabapentin, 5% lidocaine patch). Despite recent advances, there is insufficient evidence to warrant differentiation of treatment based on the etiology of neuropathic pain.[55,56]

Duloxetine is the first drug to gain FDA approval for the indication of diabetic peripheral neuropathic pain. However, randomized controlled clinical trials of duloxetine for this indication have not been published in peer-reviewed literature to date. Approval for this indication was based on data from two clinical trials conducted by the manufacturer of duloxetine.[25] These two randomized, double-blind, placebo-controlled, 12-week trials enrolled a total of 791 patients who had been diagnosed with diabetic peripheral neuropathic pain for at least six months. The patients were randomized to receive placebo, duloxetine 60 mg daily, or duloxetine 60 mg twice daily. One of the studies also included a group of patients receiving duloxetine 20 mg daily. Pain was rated by recording an average daily pain score in a diary maintained by the patient.

According to the prescribing information for duloxetine, treatment with duloxetine 60 mg one or two times daily significantly improved mean pain scores from baseline and increased the proportion of patients with at least a 50% reduction in pain scores from baseline at the end of the study period.[25] The number or percentage of patients experiencing this reduction and baeline and end-of-study pain scores were not reported. Of enrolled patients, 25% did not complete the study and were assigned 0% improvement. A description of patients who did not complete the study was not provided, and it is not clear whether these patients were included in final analysis or why they did not complete the study. From the information provided in the prescribing information, it is difficult to independently assess the efficacy of duloxetine for the treatment of diabetic peripheral neuropathic pain.