[1] TUFTS UNIV, SCH MED, DEPT PSYCHIAT, DIV CLIN PHARMACOL, BOSTON, MA 02111 USA
[2] TUFTS UNIV, SCH MED, DEPT MED, BOSTON, MA 02111 USA
[3] ADDICT RES FDN, INST CLIN, TORONTO M5S 2S1, ONTARIO, CANADA
[4] UNIV TORONTO, DEPT PHARMACOL, TORONTO M5S 1A1, ONTARIO, CANADA
[5] UNIV TORONTO, DEPT MED, TORONTO M5S 1A1, ONTARIO, CANADA