Duloxetine, pregabalin, and duloxetine + gabapentin were found to be safe and tolerable for the treatment of diabetic peripheral neuropathic pain, according to results presented today at the American Pain Society’s 30th Annual Scientific Meeting.
Gordon Irving, MD, and colleagues from Swedish Pain Center, Seattle, and the University of Washington School of Medicine, Seattle, conducted a 12-week, open-label, randomized, Phase 4 study to assess the safety and tolerability of the three therapies. Study participants had a mean duration of diabetes of 12 years and a mean duration of diabetic peripheral neuropathic pain of 4.5 years.
Patients had previously been treated with a stable dose of gabapentin (≥900mg/day for ≥5 weeks) and had an inadequate response, defined as a weekly mean 24-hour average pain score ≥4 on an 11-point Likert scale. A total of 407 patients were then randomized to duloxetine (n=138), pregabalin (n=134), or duloxetine + gabapentin (n=134) groups.
Study completion rates did not differ significantly between the groups (duloxetine, 63%; pregabalin, 71.6%; duloxetine+gabapentin, 73.3%). Discontinuation due to adverse events (AEs) was significantly greater in the duloxetine group (19.6%) vs. pregabalin group (10.4%) (P<.05); significance was not observed in comparisons of duloxetine + gabapentin (13.3%) vs. pregabalin (P=0.573) or duloxetine + gabapentin vs. duloxetine (P=0.193).
With regard to AEs, nausea, insomnia, hyperhydrosis, and decreased appetite were reported significantly more frequently by patients in the duloxetine group vs. the pregabalin group (P≤0.001); insomnia was reported significantly more frequently for the duloxetine group vs. the duloxetine + gabapentin group (P<0.05); peripheral edema was reported more frequently in pregabalin vs. duloxetine (P≤0.001); nausea, hyperhydrosis, decreased appetite, and vomiting were reported more frequently in the duloxetine + gabapentin group vs. the pregabalin group (P<0.05).
During the study, patients in the pregabalin group gained weight (1kg) while patients in the duloxetine + gabapentin and duloxetine groups lost weight (-1.06kg and -2.39kg, respectively); the between-group differences for pregabalin were significant (P<.001 each), as well as for duloxetine vs. duloxetine + gabapentin (P<0.05) groups.
Dr. Irving concluded that duloxetine, pregabalin, and duloxetine + gabapentin were found to be safe and tolerable for the treatment of diabetic peripheral neuropathic pain. The adverse event profiles for these therapies are consistent with previous reports.