Avanir Pharmaceuticals announced results of a Phase 3 randomized controlled trial of AVP-923 in the treatment of diabetic neuropathic pain. AVP-923 is a combination of dextromethorphan (DM) and quinidine (Q).

In a 13-week trial, 379 adults with daily symmetric diabetic peripheral neuropathy (DPN) leg pain for >3 months received double-blind placebo, DMQ 45/30mg, or DMQ 30/30mg, administered once daily for seven days and twice daily thereafter. Efficacy measures included four pain-rating scales applied daily using patient diaries, and another two applied at five clinic visits. On all six scales, DMQ 45/30mg was significantly superior to placebo, including the primary efficacy analysis, which utilized mixed-effects modeling to test all scores on an 11-point numerical Pain Rating Scale (P<0.0001).

Sensitivity analyses gave consistent results. Efficacy vs. placebo was also seen for diary ratings of present pain intensity, and pain interference with sleep and with activities (all P<0.0001). Among clinic-visit assessments, DMQ 45/30mg demonstrated greater leg-pain relief (P=0.0002) and greater reduction of leg-pain intensity (P=0.0286) vs. placebo. The efficacy of DMQ 30/30mg was numerically less than for 45/30mg but for most outcomes remained significantly greater versus placebo.

AVP-923 is a combination of two compounds: the active ingredient dextromethorphan hydrobromide and the enzyme inhibitor quinidine sulfate (a CYP450 2D6 inhibitor), which serves to increase the bioavailability of dextromethorphan.


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