Racial differences in drug response: isoproterenol effects on heart rate in healthy males.

It was the purpose of this study to investigate racial alterations in beta-adrenoceptor response. Two groups of healthy, male volunteers gave their consent. There were eight black Americans (mean age, 26.1 +/- 2.5 years) and eight white/Caucasian Americans (mean age 24.4 +/- 1.8 years). Each subject underwent an isoproterenol sensitivity test. There was a significant (P less than 0.05) decrease in the ratio of Emax to ED50 in the white group (25.3 +/- 6.4) compared with the black group (37.1 +/- 12.4). Over the dose range of 0.1 to 1.0 micrograms there was a significant increase in response at both the 0.25- and the 0.5-microgram dose (P less than 0.05), with the black American group appearing to respond with a greater rate of rise in heart rate following the initial doses.