Objective: The current analysis examines the response profile in patients receiving duloxetine for the management of diabetic peripheral neuropathic pain (DPNP).
Patients/design: Data were pooled from three double-blind, randomized, placebo-controlled 12-week acute therapy trials of patients with DPNP of at least 6 months' duration. Study 1 (N = 457) had treatment groups of duloxetine 20 mg once daily (QD), 60 mg QD, 60 mg twice daily (BID), and placebo; Studies 2 (N = 334) and 3 (N = 348) compared duloxetine 60 mg QD and 60 mg BID with placebo. The primary efficacy measure in each study was the weekly mean score of the 24-hour average pain severity. Treatment response was defined as a 30% reduction in pain severity, although some analyses were repeated using alternative response criteria (50% reduction, or 2-point reduction, in pain severity).
Results: Consistently across the three studies, response rates at endpoint were significantly higher among patients receiving duloxetine (60 mg QD or 60 mg BID) than among those receiving placebo, regardless of the chosen response criterion (30% reduction, 50% reduction, or 2-point reduction in weekly mean of 24-hour average pain severity). The proportion of patients achieving pain relief in the duloxetine treatment groups was significantly greater than that in the placebo group at Week 1 and at all subsequent study visits to the end of acute phase therapy. Using diary data (24-hour average pain severity) from the first 7 days of treatment, the first significant separation from placebo in pain severity reduction for duloxetine 60 mg QD occurred at Day 1 (Study 1), Day 2 (Study 2), and Day 4 (Study 3), while significant separation in response rates first occurred at Day 3 when using pooled data.
Conclusions: Patients with DPNP receiving duloxetine 60 mg QD or 60 mg BID had significantly higher rates of treatment response, when compared with patients receiving placebo, regardless of the chosen response criterion. Response to duloxetine treatment tended to occur early in therapy.