Concept

Procaïnamide

Résumé
Procainamide (PCA) is a medication of the antiarrhythmic class used for the treatment of cardiac arrhythmias. It is classified by the Vaughan Williams classification system as class Ia; thus it is a sodium channel blocker of cardiomyocytes. In addition to blocking the INa current, it inhibits the IKr rectifier K+ current. Procainamide is also known to induce a voltage-dependent open channel block on the batrachotoxin (BTX)-activated sodium channels in cardiomyocytes. Procainamide is used for treating ventricular arrhythmias: ventricular ectopy and tachycardia and supraventricular arrhythmias: atrial fibrillation, and re-entrant and automatic supraventricular tachycardia. For example, it can be used to convert new-onset atrial fibrillation, and although was initially thought to be suboptimal for this purpose, a growing body of literature is amounting in support for this exact cause. It is administered by mouth, by intramuscular injection, or intravenously. It has also been used as a chromatography resin because it somewhat binds protein. There are many side effects following the induction of procainamide. These adverse effects are ventricular dysrhythmia, bradycardia, hypotension and shock. The adverse effects occur even more often if the daily doses are increased. Procainamide may also lead to drug fever and other allergic responses. There is also a chance that drug-induced lupus erythematosus occurs, which at the same time leads to arthralgia, myalgia and pleurisy. Most of these side effects may occur due to the acetylation of procainamide. There is a close line between the plasma concentrations of the therapeutic and toxic effect, therefore a high risk for toxicity. Many symptoms resemble systemic lupus erythematosus because procainamide reactivates hydroxylamine and nitroso metabolites, which bind to histone proteins and are toxic to lymphocytes. The hydroxylamine and nitroso metabolites are also toxic to bone marrow cells and can cause agranulocytosis. These metabolites are formed due to the activation of polymorphonuclear leukocytes.
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