1. Medicinal Biochemistry Department, Burroughs Wellcome Co., 3030 Cornwallis Road, Research Triangle Park, North Carolina 27709, USA
2. Department of Medicine, University of Ghana Medical School, PO Box 4226, Accra, Ghana
3. Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Ife, Ile-Ife, Nigeria
4. School of Pharmacy and Pharmacology, University of Bath, Bath, UK
5. Clinical Pharmacology Unit, Royal United Hospital, Bath