Racial differences in drug response: isoproterenol effects before and after propranolol

A review and assessment of potential sources of ethnic differences in drug responsiveness

The International Conference on Harmonization (ICH) E5 guidelines were developed to provide a general framework for evaluating the potential impact of ethnic factors on the acceptability of foreign clinical data, with the underlying objective to facilitate global drug development and registration. It is well recognized that all drugs exhibit significant inter-subject variability in pharmacokinetics and pharmacologic response and that such differences vary considerably among individual drugs and depend on a variety of factors. One such potential factor involves ethnicity. The objective of the present work was to perform an extensive review of the world literature on ethnic differences in drug disposition and responsiveness to determine their general significance in relation to drug development and registration. A few examples of suspected ethnic differences in pharmacokinetics or pharmacodynamics were identified. The available literature, however, was found to be heterologous, including a variety of study designs and research methodologies, and most of the publications were on drugs that were approved a long time ago.

Hypertension in black people: study of specific genotypes and phenotypes will provide a greater understanding of interindividual and interethnic variability in blood pressure regulation than studies based on race

Hypertension is more frequent and more severe in some Black populations. Although many studies have focused on hypertension in black people in an attempt to understand the genetic and environmental factors that regulate blood pressure, this approach has not been productive. Study of the relationship between specific phenotypes and genotypes, both within and across ethnic groups, is more likely to advance our understanding of the regulation of blood pressure than studies focused on race and blood pressure.

Race and hypertension. What is clinically relevant?

Hypertension, once considered rare in Africa, occurs frequently in most Black populations outside of the continent as well as within more urban areas of Africa. The frequency of hypertension in Black citizens of the US is among the highest in the world. Pathophysiological mechanisms suggest the frequency of salt-sensitive blood pressure is more common in Black patients. More Black than White patients initially present with volume expansion. However, in Black patients there appears to be no significant relationship between plasma renin activity, plasma volume and blood pressure. The syndrome of insulin resistance has also been reported in African Americans. Future studies should address this issue, both because it relates to identifying individuals at risk for development of high blood pressure and because it has implications for initial selection of antihypertensive therapy. Hypertensive kidney disease is prevalent in Black people. Lowering the blood pressure with diuretic-based therapies has not been shown to delay or prevent the loss of kidney function in patients with this condition, suggesting that this treatment approach may not be optimal. Lifestyle modifications remain the initial therapeutic regimen. Because diuretics and beta-blockers have been shown to reduce cardiovascular morbidity and mortality in controlled clinical trials, they are preferred therapies. The Hypertension Detection and Follow-up Program showed significant reductions in morbidity and mortality in Black patients using primarily diuretic-based therapies. However, controversy persists regarding use of diuretics since some investigators believe that greater reductions in overall cardiovascular risk may be achieved in Black patients using other agents. These agents may eventually be able to exert a beneficial cardiovascular effect in addition to and independent of their blood pressure-lowering effect. Long term data documenting reduced morbidity and mortality rates with other agents are needed for all populations, particularly in Black hypertensive patients.

Are there beta-adrenergic receptor response differences between racial groups?

Beta-adrenergic receptor (BAR) agonists and antagonists are among the most widely used drugs in America today. This review highlights the importance of cross-racial studies in evaluating BAR effects because heterogeneity in pharmacologic response among humans exists. Clinicians and basic scientists in the drug development industry need to acknowledge racial differences in antihypertensive drug responses and prevent various racial groups from being underrepresented in clinical trials. This article reviews the influence of race on BAR responses with emphasis on blacks and whites. Information from patients with hypertension, healthy volunteers, and in vitro studies is presented.