[1] Univ Alberta, Fac Pharm & Pharmaceut Sci, Edmonton, AB T6G 2E1, Canada
[2] Univ Sao Paulo, Fac Pharmaceut Sci, BR-05508000 Sao Paulo, Brazil
[3] Merck & Co Inc, Basic Pharmaceut Sci, West Point, PA 19486 USA
[4] Rhodes Univ, Fac Pharm, ZA-6140 Grahamstown, South Africa