Pharm Chapter 45 - Calcium Channel Blockers Study Questions and Correct Answers

Prototype for calcium channel blocker that affect the heart and blood vessels Verapamil Prototype for calcium channel blocker that is a dihydropyridines: Agents that act mainly on blood vessels Nifedipine Safety Alert: Immediate-release nifedipine has been associated with increased mortality in patients with myocardial infection and unstable angina. The national heart, lung and blood institute recommends that this drug is used with great caution, if at all. It is important to note that these adverse effects have not been associated with sustained release forms of the drug. Safety Alert: Other IR CCBs than immediate release nifedipine have been associated with an increased risk of myocardial infarction in patients with hypertension. It is important to note that these adverse effects have not been associated with long acting drugs. Calcium channels gated pores in the cytoplasmic membrane that regulate calcium entry into cells. Calcium entry in blood vessels causes vasoconstriction, and hence calcium channel blockade causes vasodilation. Calcium entry in the heart increases heart rate, AV conduction, and myocardial contractility, so calcium channel blockade has the opposite effects. Calcium channels are coupled to beta1 receptors in the heart Activation of beta1 receptors enhances calcium entry, as a result calcium channel blockade and beta blockade have identical effects on cardiac function In therapeutic doses, nifedipine and other dihydropyridines act primarily on VSM Verapamil and Diltiazem in therapeutic doses Act on VSM and on the heart. Suppress AV conduction and are used to treat cardiac dysrhythmias (in addition to hypertension and angina pectoris)