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Pharmacology: Calcium-channel blocker.
Nifedipine is a calcium antagonist of the 14-dihydropyridine type. Calcium antagonists reduce the transmembranal influx of calcium ions through the slow calcium channel into the cell. Nifedipine acts particularly on the cells of the myocardium and the smooth muscle cells of the coronary arteries and the peripheral resistance vessels. Parallel to this, nifedipine reduces the oxygen requirement by lowering peripheral resistance (afterload). With long-term use, nifedipine can also prevent the development of new atherosclerotic lesions in the coronary arteries.
At the beginning of the nifedipine treatment, there may be a transient reflex increase in heart rate and thus in the cardiac output. However, this increase is not enough to compensate for the vasodilation, thereby causing lowering of blood pressure. Nifedipine increases sodium and water excretion both in short-term and long-term use.
In Raynaud's syndrome, nifedipine can prevent or reduce the occurring digital vasospasm.
The t½ of nifedipine is 4-6 hrs.
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