Alterations in the rate of any of these processes can account for significant changes in the drug's effect on the patient. Likewise, changes in the functional status of any of the organs alter dose requirements in a given patient. Most of the available antiarrhythmic drugs can be classified according to whether they exert blocking actions, predominantly on sodium, potassium or calcium channels, and whether they block beta-adrenoceptors. The actions of these drugs are quite complex and depend on tissue type, the degree of acute or chronic damage, heart rate, membrane potential, the ionic compositions of the extracellular milieu and other factors. Many drugs exhibit actions that belong in multiple categories, or operate indirectly, such as by altering hemodynamics, myocardial metabolism or automatic neural transmission.
Some drugs have active metabolites that exert different effects from the parent compound.
Not all drugs in the same class have identical effects, e.g., bretylium, sotalol and amiodarone are dramatically different, while some drugs in different classes have overlapping actions, e.g., class IA and IC drugs. In vitro studies on healthy fibers usually establish the properties of antiarrhythmic agents rather than their antiarrhythmic properties. Arrhythmogenic substrate Regional differences of drug tissue concentrations For more information on treatment for cardiac arrhythmias, click on these links. For more information on pharmacological therapy for cardiac arrhythmias, click on these links. The Post-Graduate Education Committee of the Council on Clinical Cardiology has prepared this slide set.