Verapamil dihydropyridines contrasted

Nifedipine is just one of many 1,4-dihydropyridines in contrast, the remaining three classes have only one representative agent. Nifedipine is selective for vascular smooth muscle and is therefore an excellent hypotensive. However, it can cause tachycardia (i.e., an excessive increase in heart rate), and is therefore prescribed with [3-adrenergic blockers. Verapamil and diltiazem have a direct effect on the heart, do not cause tachycardia, and are therefore the ideal antianginal agents. Phenylalkylamines need a 1- to 2-week lag period until their antianginal effect is evident. Bepridil has a relatively non-selective action. 

Bay K 8644 (30) is a novel 1,4-dihydro-pyridine derivative.In contrast to the nifedipine-like dihydropyridines which have calcium antagonistic actions, 30 promotes the influx of calcium ions and therefore produces positive inotropic and vasoconstrictor effects. In the isolated guinea pig heart, the positive inotropic effect begins at 10" mol/1 and reaches a plateau at 10" mol/1. In various models the pharmacological effects of 30 were found to be competitively antagonized by nifedipine, but not by other calcium antagonists such as verapamil or diltiazem. 

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