ADVERSE-EFFECTS OF CLASS-I ANTIARRHYTHMIC DRUGS

Class I antiarrhythmic drugs are characterised by their ability to blo ck the fast inward sodium current in cardiac muscle tissue. However, a t the same time, they can be responsible for various effects involving other organs and systems. Although some of these effects can be helpf ul in specific situations, most of them, such as their pro-arrhythmic propensity, are deleterious. Some of the adverse effects of class I an tiarrhythmic drugs are directly linked to sodium-channel blockade (con duction disorders, haemodynamic perturbations, and digestive and neuro logical effects), while others are linked to other specific pharmacolo gical properties (e.g. atropinic, or alpha- or beta-adrenergic blockad e) or to nonspecific properties (idiosyncratic hypersensitivity, and h aematological, dermatological or hepatic reactions). Other adverse eff ects are associated with complex interactions between class I antiarrh ythmics and individual predisposing factors, trigger mechanisms and ph ysiological factors (including concomitant drug treatment). These nume rous variations and interactions within a specific environment and und erlying disorder might be of pharmacological or/and pharmacokinetic or igin, making analysis of the true liability of the class I drugs very difficult when adverse effects occur.