Which of the following drugs lack vasodilatory properties that is effective in angina?
Correct Answer: Metoprolol
Description: Metoprolol: It is the prototype of cardioselective (β1) blocker; nearly 50 times higher dose is needed to block isoprenaline induced vasodilation. Some measure of inverse agonistic activity on β1 receptors has also been demonstrated. It is less likely to worsen asthma, but is not entirely safe. It may be preferred in diabetics receiving insulin or oral hypoglycaemics. Patients who complain of cold hands and feet while on propranolol, do better on metoprolol.
First pass metabolism of metoprolol is less marked than propranolol, but 90% or more is ultimately hydroxylated by CYP2D6 before excretion. There are 'extensive' and 'poor' hydroxylators of metoprolol (CYP2D6 alleles); the latter may require a lower dose.
Side effects of metoprolol are milder. It is generally given orally for hypertension, angina and CHF, but i.v. injection (5-15 mg) has been used in myocardial infarction provided bradycardia is absent.
Key concept:
Beta-blockers do not cause vasodilation.
Reference: Essentials of Medical Pharmacology Eighth Edition KD TRIPATHI page no 162
Category:
Pharmacology
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