Ethnic differences in response to non-selective beta-blockade among racialgroups in Malaysia

<(Objective)under bar>: To determine whether racial differences in response to blockade of beta receptors occur among racial groups in Malaysia that a re the Malays, Indians and Chinese. <(Subjects, materials and method)under bar>: 35 healthy male volunteers representing the 3 main racial groups in M alaysia (12 Malays, 12 Chinese and 11 Indians) were studied in a randomized , placebo-controlled, crossover and single-blind design. Propranolol 80 mg 12-hourly was given orally for 48 hours. Six hours after the last dose subj ects attended an exercise session where resting and exercise heart rate, bl ood pressure, plasma potassium and glucose levels, resting FEV1 and plasma propranolol concentrations were recorded. <(Results)under bar>: No signific ant difference in plasma propranolol (mean +/- SEM) levels was seen between races six hours after the last dose (Malays, 59.7 +/- 8.8 ng/ml, Indians, 67.6 +/- 19.3 ng/ml, Chinese, 58.4 +/- 7.9 ng/ml). Chinese were least sensi tive to the bradycardic and hypotensive effects of propranolol at rest and exercise. Indians and Malays had significant reduction of supine systolic b lood pressure with propranolol but not Chinese. Comparison of percentage re ductions of systolic blood pressure at supine, sitting and exercise by repe ated measure analysis showed the Malays to have significantly higher change compared to the Chinese (p = 0.022). Similarly, comparison of percentage r eductions of heart rate at supine, sitting and exercise by repeated measure analysis showed the Malays to have significantly higher change compared to the Chinese (p = 0.040). Average change in potassium concentrations at pea k exercise and recovery showed the Indians to have significantly higher inc rease in potassium levels with propranolol compared to the Malays (p = 0.03 8). However, no significant interethnic difference was seen in the reductio n of glucose levels at rest, peak exercise or recovery. Also, no significan t interethnic difference was seen in reduction of FEV1 values. <(Conclusion )under bar>: We, therefore, conclude that ethnic differences in response to blockade of P-receptors exist among racial groups in Malaysia. These diffe rences were seen at similar plasma drug levels between races suggesting eth nic differences in drug sensitivity, rather than differences in drug dispos ition.