1. School of Veterinary Medicine, Department of Clinical Studies, University of Pennsylvania, New Bolton Center Campus, Kennett Square, Pennsylvania 19348, PA Equine Toxicology and Research Laboratory, Department of Chemistry, West Chester University, 220 East Rosedale Avenue, West Chester, Pennsylvania 19382, and Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-1778