1. Center for Clinical Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania 15217, Department of Drug Metabolism, Merck Research Laboratories, West Point, Pennsylvania 19486, Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195, Laboratory of Metabolism, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, and Department of Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, West Virginia 26506