Racial differences in drug responses--a comparative study of trimazosin and alpha 1-adrenoceptor responses in normotensive Caucasians and West Africans.

The possible racial differences in alpha 1-adrenoceptor responsiveness and the blood pressure and heart rate responses following alpha 1-adrenoceptor antagonism with trimazosin have been investigated in matched groups of six Caucasians and six Nigerians. There were no significant differences between the racial groups in the blood pressure and heart rate responses to oral (200 mg) and intravenous (100 mg) trimazosin. alpha 1-adrenoceptor responsiveness was similar in both groups after placebo and following both active treatments. There were only minor pharmacokinetic differences with the Caucasians having a larger volume of distribution, and a longer terminal elimination half-life for the metabolite, 1-hydroxy-trimazosin. These results suggest a similarity in peripheral vascular alpha 1-adrenoceptor mechanisms and show no major significant racial differences in the pharmacokinetics and pharmacodynamics of trimazosin.