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Differing beta-blocking effects of carvedilol and metoprolol
K Stoschitzky1, G Koshucharova, R Zweiker
1Medizinische Universitätsklinik, Abteilung für Kardiologie, Graz, Austria. kurt.stoschitzky@kfunigraz.ac.at
European Journal of Heart Failure
|May 30, 2001
Summary
Metoprolol and carvedilol show distinct beta-blocking effects. Metoprolol more effectively reduces heart rate during exercise, while carvedilol
Area of Science:
- Pharmacology
- Cardiovascular Medicine
- Clinical Trials
Background:
- Metoprolol is a selective beta(1)-adrenergic antagonist, while carvedilol is a non-selective beta-blocker with alpha(1)-adrenoceptor blockade.
- Metoprolol can increase beta-adrenoceptor density and decrease melatonin release; carvedilol does not exhibit these typical beta-blocker effects.
Purpose of the Study:
- To compare the oral beta-blocking effects of metoprolol and carvedilol in healthy individuals.
- To assess the impact of different dosages on heart rate and blood pressure.
Main Methods:
- A randomized, double-blind, cross-over study involving 12 healthy male volunteers.
- Administration of single oral doses of metoprolol (50, 100, 200 mg) and carvedilol (25, 50, 100 mg) compared to placebo.
- Measurement of heart rate and blood pressure at rest, during exercise, and during recovery.
Main Results:
- Metoprolol demonstrated a greater reduction in heart rate during exercise compared to carvedilol.
- Metoprolol consistently decreased resting heart rate with increasing doses.
- Carvedilol showed minimal effect on resting heart rate, with higher doses not significantly differing from placebo, potentially due to alpha-blockade-induced vasodilation.
Conclusions:
- Carvedilol provides a clinically relevant beta-blockade during exercise, though slightly less potent than metoprolol.
- Carvedilol's resting heart rate effects are weak, possibly due to its alpha-blocking properties, which may explain its milder side-effect profile compared to metoprolol.
- Findings may inform the interpretation of trials like COMET but require caution due to study on healthy subjects, not patients.
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