Calcium Channel Antagonists

The L-type calcium channel, whose pore is formed by the CACNA1C alpha-1C subunit, opens on membrane depolarisation and admits calcium into the cytoplasm, which in turn triggers calcium release from the sarcoplasm; it is the channel that couples excitation to contraction in the heart, is required for normal regulation of heart rhythm, and is required for contraction of arterial smooth muscle and so for normal blood pressure. Drugs in this class reduce calcium flux through that channel - UniProt records inhibition by dihydropyridines such as isradipine and by nifedipine - so vascular smooth muscle relaxes and cardiac contractility and conduction fall. A drug belongs here because it reduces calcium flux through a voltage-gated calcium channel; the dihydropyridine site is on the channel protein itself, which is why MED-RT's narrower child class is named L-Calcium Channel Receptor Antagonists.