ABSTRACT
Cardioactive drugs represent one of the most commonly prescribed groups of therapeutic agents to treat cardiac arrhythmias, congestive heart failure, and hypertension. In most instances, despite significant differences in chemical structure and properties and their therapeutic applications, many of these drugs exert their pharmacological effects by similar mechanism through controlling electrical conduction system and/or phases of the cardiac action potential [1,2]. Class I drugs, such as lidocaine and quinidine, block sodium influx in the first phase of the action potential, resulting in its prolongation. Class II agents include drugs like propranolol, which is a beta-adrenergic receptor antagonist that inhibits the chronotropic and sympathomimetic effects of epinephrine and norepinephrine on the heart, as well as the vasculature and circulatory system. Class III cardiotropic drugs, such as amiodarone, act to block repolarization by potassium currents and, thereby, prolong the refractory period and the overall action potential. Class IV drugs, characterized by verapamil and nifedipine, are calcium channel blockers that decrease conduction through the atrioventricular (A-V) node and shorten the plateau of the cardiac action potential.
