Racial Differences in Drug Response: Isoproterenol Effects Before and After Propranolol

The aim of this study was to determine in young, healthy men the relative contribution of pharmacodynamic factors inherent between two groups known to respond differently to hypertensive therapy. Black (n = 10) and white (n = 10) men received an isoproterenol sensitivity test before and after propranolol (0.1 mg/kg, then 50 µg/min). There were greater increases (twofold) in systolic BP following the 1.0- and 1.5-µg isoproterenol dose (P < 0.05) in the black group. During propranolol there were no differences in free (1)-propranolol concentrations between the groups; however, propranolol decreased resting heart rate in the white group more than in the black group (P < 0.05). Cardiac index decreased less in the black group compared to the white group (P < 0.05). Following the second isoproterenol challenge, there again were greater increases in systolic BP in the black group at both the 10- and the 20-µg isoproterenol dose (P < 0.05). Our study has highlighted the importance of cross-racial studies in evaluating drug effects.