1. From the Divisions of Clinical Pharmacology (S.R.R., I.B., D.R.) and Cardiovascular Medicine (P.C.Y., B.K.B., S.Y.P.), Departments of Medicine, Pharmacology (S.R.R., I.B., D.R.), Biostatistics (D.W.B.), and Neurology (D.R.), Vanderbilt University, Nashville, Tenn.