Evaluating the maintenance of effect of duloxetine in patients with diabetic peripheral neuropathic pain

Background To evaluate the maintenance of effect of duloxetine 60 mg QD over 26 weeks in patients with diabetic peripheral neuropathic pain (DPNP). Methods Adult patients with DPNP and Brief Pain Inventory (BPI) open-label study with duloxetine 24-h average pain >= 4 were treated in this Q 60 mg QD for 8 weeks. Responders (>= 30% pain reduction) continued on duloxetine 60 mg QD (maintenance arm) for 26 weeks while non-responders had duloxetine increased to 120 mg QD (rescue arm). The primary outcome measure was the mean change from baseline (Week 8) to endpoint (Week 34) in BPI average pain in the maintenance arm. A number of secondary efficacy measures, as well as safety and tolerability, were assessed. Results Two hundred and sixteen patients entered the study and their baseline BPI average pain was 5.9. Thirty-two patients (15%) discontinued during the acute phase. One hundred and fifteen (53%) patients were found to be responders to 60 mg dose and they entered the maintenance arm. During the maintenance period they reported a mean change of BPI average pain of 0.35, with 0.79 as the upper bound of the one-sided 97.5% CI, which was less than the pre-specified non-inferiority margin of 1.5 (p < 0.001). Non-responders, upon dose increase to 120 mg QD, reported a statistically significant pain reduction. Total of 119 patients completed either arm of the study. Twenty patients experienced 27 serious adverse events including one death. Conclusion In this open-label study, the effect of duloxetine 60 mg QD in patients with DPNP was maintained over 6-month period. Copyright (C) 2009 John Wiley & Sons, Ltd.