Introduction to CV Pharmacology - Orlando Health

CV Pharmacology
Antidysrhythmics: Class IV
Calcium is critical to heart function due to its effect on cardiac output by increasing contractility
and conductivity. Calcium channel blockers decrease contractility of the myocardium and slow
conduction through the SA and AV nodes by inhibiting the influx of calcium and sodium during
phase 2 of the action potential. These actions result in prolonging both the absolute and relative
refractory periods. Drugs in this class also produce vasodilation of the peripheral and coronary
arteries, thereby increasing the supply of oxygenated blood to the myocardium and reducing
myocardial workload to reduce myocardial oxygen demand.
Calcium channel blocker categories
Two types of calcium channel blockers exist because they exert different effects.
Calcuim channel blockers known as (nondihydropyridines): cause coronary artery
vasodilation, decrease heart rate, and decrease conduction through the SA and AV nodes. They
are utilized to treat atrial dysrhythmias, angina, and hypertension.
Diltiazem (Cardizem, Dilacor XR, Tiazac) verapamil (Calan, Isoptin, Verelan PM)
Calcuim channel blockers known as (dihydropyridines): dilate peripheral blood vessels
without affecting heart rate or contractility. They are utilized to manage hypertension and will
be discussed later in this SLP.
Nifedipine (Procardia, Adalat), amlodipine (Norvasc), felodipine (Plendil), isradipine
(DynaCirc), nicardipine (Cardene), and nisoldipine (Sular)
The following page has a summary chart on the actions and indications for calcium channel
blockers.
Precautions
Short acting nifedipine capsules (Procardia ® , Adalat ® ) are not recommended for acute
blood pressure reduction nor for chronic hypertension management due to risk of
profound hypotension, cerebral ischemia or stroke, and/or death.
Nifedipine should NEVER be administered sublingually or as a “bite and swallow” order.
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