Which of the following effects of calcium channel blockers causes a reduction in blood pressure?
A. Increased cardiac output.
B. Decreased peripheral vascular resistance.
C. Decreased renal blood flow.
D. Calcium influx into cardiac muscles.
Correct Answer: B. Decreased peripheral vascular resistance.
One of the effects of calcium channel blockers is to decrease peripheral vascular resistance. Cardiovascular indications include hypertension, coronary spasm, angina pectoris, supraventricular dysrhythmias, hypertrophic cardiomyopathy, and pulmonary hypertension. In addition to these, they are also prescribed for Raynaud phenomenon, subarachnoid hemorrhage, and migraine headaches. The other options describe the opposite effects of calcium channel blockers.
Option A: The non-dihydropyridines have inhibitory effects on the sinoatrial (SA), and atrioventricular (AV) nodes are resulting in a slowing of cardiac conduction and contractility. This allows for the treatment of hypertension, reduces oxygen demand, and helps to control the rate in tachydysrhythmias.
Option C: The dihydropyridines, in therapeutic dosing, have a little direct effect on the myocardium, and instead, are more often peripheral vasodilators, which is why they are useful for hypertension, post-intracranial hemorrhage associated vasospasm, and migraines.
Option D: Calcium channel antagonists block the inward movement of calcium by binding to the L-type “long-acting” voltage-gated calcium channels in the heart, vascular smooth muscle, and pancreas.