Maximal aerobic power and blood pressure in normotensive subjects after acute and chronic administration of metoprolol

Abstract

The acute and long-term effects of the beta 1-adrenoceptor blocking agent metoprolol on blood pressure and maximal aerobic power (Wmax) were studied in 10 healthy subjects. Progressive maximal bicycle ergometer tests were performed after intravenous administration of placebo and metoprolol (0.15 mg . kg-1 and 0.30 mg . kg-1), and at the end of 4-week treatment periods with placebo, conventional metoprolol (C-M) and slow-release metoprolol (SR-M). The reduction in maximal exercise heart rate (HRmax) was correlated with the log plasma metoprolol concentration. Despite a reduction in HRmax of 23 beats/min after 0.15 mg . kg-1 metoprolol, Wmax was unaffected. After 0.30 mg . kg-1 HRmax was reduced by 40 beats/min and Wmax by 5.0%. During chronic treatment, the reductions in HRmax and Wmax were 48 beats/min and 7.5% (C-M) and 45 beats/min and 6.9% (SR-M), respectively. Resting systolic blood pressure was not changed after acute administration of metoprolol but it was reduced during chronic beta-blocker treatment. Resting diastolic blood pressure was not affected after acute or chronic treatment. Exercise systolic blood pressure remained unchanged after 0.15 mg . kg-1 metoprolol i.v. The fall in exercise systolic pressure after 0.30 mg . kg-1 metoprolol i.v. (18 +/- 5 mmHg) was significantly smaller than that during chronic treatment (30 +/- 6 mmHg C-M; 30 +/- 6 mmHg, SR-M). During chronic metoprolol treatment a certain % HRmax corresponded to a higher % Wmax than during placebo treatment, but the shift appeared to be of minor practical importance.(ABSTRACT TRUNCATED AT 250 WORDS)