Avanir Pharmaceuticals has reported that its Phase II clinical trial of the investigational drug AVP-923 (dextromethorphan / quinidine) for the treatment of central neuropathic pain in patients with multiple sclerosis did not meet the primary efficacy endpoint. In the study, AVP-923 treated patients experienced levels of pain reduction commensurate with those observed in similar studies and the improvement in pain scores from baseline reached statistical significance; however, there was no diff...