Antiarrhythmic agents. Receptor hypothesis explains mechanisms of action
Bjørnstad, H.; Refsum, H.
Tidsskrift for den Norske Laegeforening Tidsskrift for Praktisk Medicin Ny Raekke 111(26): 3187-3189
1991
ISSN/ISBN: 0029-2001 PMID: 1658976 Document Number: 374553
Antiarrhythmic drugs are usually classified according to Vaughan Williams' classification I-IV. Class I includes the membrane stabilizers, class II includes the beta-blockers, drugs in class III lengthen the cardiac action potential and refractory period and class IV includes the calcium blockers. The effect of most antiarrhythmic drugs changes with heart rate and the level of myocardial depolarization, and these changes in effect can be explained by the modulated receptor hypothesis. Most class I antiarrhythmic drugs have greatest antiarrhythmic effect during periods of fast heart rate and in depolarized ischemic myocardium, and this might be attributed to greater affinity of the drugs for open or inactivated sodium channels. Most class III antiarrhythmic drugs have greatest effect during periods of slow heart rates, which may be attributed to greater affinity for closed potassium channels.