The pharmacokinetic characteristics of procainamide:
Oral bioavailability Onset of action Peak response Duration of action Plasma half-life Primary route of metabolism Primary route of excretion Therapeutic serum concentration
Hepatic; active metabolite
50-60% renal (unchanged)
Procainamide is an effective antiarrhythmic agent when given in sufficient doses at relatively short (3-4 hours) dosage intervals. Procainamide is useful in the treatment of premature atrial contractions, paroxysmal atrial tachycardia, and atrial fibrillation of recent onset. Procainamide is only moderately effective in converting atrial flutter or chronic atrial fibrillation to sinus rhythm, although it has value in preventing recurrences of these arrhythmias once they have been terminated by direct current (DC) cardioversion.
Procainamide can decrease the occurrence of all types of active ventricular dysrhythmias in patients with acute myocardial infarction who are free from A-V dissociation, serious ventricular failure, and cardiogenic shock. About 90% of patients with ventricular premature contractions and 80% of patients with ventricular tachycardia respond to procainamide administration.
Although the spectrum of action and electrophysio-logical effects of quinidine and procainamide are similar, the relatively short duration of action of pro-cainamide has tended to restrict its use to patients who are intolerant of or unresponsive to quinidine.
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