Perbezaan respon terhadap halangan reseptor beta di kalangan kaum-kaum di Malaysia
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Date
1998
Authors
Ghulam Rasool, Aida Hanum
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Abstract
Not much is known regarding racial differences in response to drugs amorig
racial groups m Malaysia. Therefore we conducted this clinical study which is
randomised, placebo-controlled, crossover and single blinded to see if racial
differences in response to blockade of beta1 and beta2 receptors by a beta-blocker exist
among the main ethnic groups in Malaysia.
Thirty- five healthy, male volunteers were involved in this study, grouped
into 3 racial groups consisting of 12 Malays, 11 Indian and 12 Chinese. Subjects were
given orally either propranolol 80mg or placebo tablets twice a day for a total of 4
doses. Six hours after the last dose subjects attended an exercise session where
parameters such as resting and exercise heart rate, resting and exercise blood pressure, _
resting and exercise potassium and glucose blood levels, plasma propranolol levels and
resting forced expiratory volume in one second were recorded. A simple and sensitive
method to quantify plasma propranolol concentration using high perfomuince liquid
chr,omatography with ultraviolet detection was also developed.
No significant racial difference was seen for weight, age and plasma
propranolol levels. However, significant interethnic differences in response to
blockade of beta1 and beta2 receptors were seen. Chinese were least sensitive to the
bradycardic and hypotensive effects of propranolol at rest and at exercise. The
absolute (9.2bpm vs 15.6bpm; p=0.02) and percentage reduction (14% vs 22.5%;
p=0.025) of supine heart rate in the Chinese were less than those of the Malays.
Similarly, percentage reduction of resting systolic blood pressure in the Chinese was
less than those of the Malays, and this is true in the sitting (3% vs 1 0.35%; p=0.04)
and supine (3.8% vs 9.5%; p=0.039) positions. Unlike the Malays and Indians who
showed significant reduction in supine systolic blood presssure, no significant
reduction in those ofthe Chinese was seen with propranolol.
In terms of beta2 receptor blockade, Indians showed higher increase of plasma
potassium levels at peak exercise when given propranolol compared to the Malays
(0.61mmolll vs 0.07mmolll; p=0.045). No significant interethnic difference in the
reduction of glucose levels at peak exercise was seen when given propranolol.
In conclusion, when the three main racial groups in Malaysia were given equal
doses of propranolol, at steady state there were significant differences m
pharmacodynamic responses._ between them despite there being no significant
difference in the levels of plasma propranolol.
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Keywords
Reseptor beta