Different beta-blocking effects of carvedilol and bisoprolol in humans

Journal of Clinical and Basic Cardiology 2001; 4 (1): 53-56

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Keywords: Betablocker,  Bisoprolol,  Carvedilol,  Herzinsuffizienz,  beta-blocker,  Bisoprolol,  Carvedilol,  heart failure

Bisoprolol is a beta1-selective beta-adrenergic antagonist while carvedilol is a non-selective beta-blocker with additional blockade of alpha1-adrenoceptors. Administration of bisoprolol has been shown to cause up-regulation of beta-adrenoceptor density and to decrease nocturnal melatonin release, whereas carvedilol lacks these typical effects of beta-blocking drugs. The objective of the present study was to investigate beta-blocking effects of bisoprolol and carvedilol in healthy subjects. We compared the effects of single oral doses of clinically recommended amounts of bisoprolol (2.5, 5 and 10 mg) and carvedilol (25, 50 and 100 mg) to those of placebo in a randomised, double-blind, cross-over study in 12 healthy male volunteers. Three hours after oral administration of the drugs heart rate and blood pressure were measured at rest, after 10 min. of exercise, and after 15 min. of recovery. Bisoprolol tended to decrease heart rate during exercise (-17 %, -21 % and -25 %) to a slightly greater extent than carvedilol (-17 %, -18 % and -21 %) although the differences between the two drugs were not significant. At rest, increasing doses of bisoprolol further decreased heart rates (63, 61 and 53 beats/min) whereas increasing doses of carvedilol resulted in increasing heart rates (63, 63 and 68 beats/min), with 100 mg carvedilol failing to differ significantly from placebo (71 beats/min). We conclude that clinically recommended doses of carvedilol cause clinically relevant beta-blockade in healthy humans predominantly during exercise where it appears to be slightly less effective than bisoprolol. On the other hand, the effects of carvedilol on heart rate at rest appear to be weak or non-existent, particularly in subjects with a low sympathetic tone, whereas bisoprolol is a potent beta-blocker both at rest and during exercise. The weak clinical consequences of beta-blocking effects of carvedilol might possibly be caused by a reflex increase in sympathetic drive due to a decrease in blood pressure resulting from the alpha-blocking effects of the drug. J Clin Basic Cardiol 2001; 4: 53-56.