procainamidi

Procainamide, or procainamidi in some languages, is an antiarrhythmic medication classified as a class IA (sodium channel blocker). It is used to treat certain ventricular and atrial arrhythmias and is sometimes employed for rapid control of sustained tachyarrhythmias when other treatments are unsuitable.

Mechanism and pharmacokinetics

Procainamide blocks fast sodium channels, slowing conduction and prolonging the action potential and the QT interval. This results in lengthened refractory periods and a reduction in reentrant circuits. It can be given intravenously for acute management or orally for maintenance. The drug is rapidly absorbed and extensively metabolized in the liver to N-acetylprocainamide (NAPA), an active metabolite that also prolongs repolarization. Both procainamide and NAPA are cleared by the kidneys; their half-lives vary with acetylation status and renal function.

Medical uses

It is used for acute treatment of ventricular arrhythmias and for certain supraventricular arrhythmias, including atrial fibrillation with rapid ventricular response in some settings. Because of risks such as proarrhythmia and drug-induced lupus, it is less commonly used as a first-line agent today and is typically reserved for specific clinical scenarios or situations where other antiarrhythmics are unsuitable.

Adverse effects and safety

Common concerns include hypotension with intravenous administration, QRS widening, and QT prolongation, which can predispose to torsades de pointes in susceptible patients. A hallmark long-term adverse effect is drug-induced lupus-like syndrome, with potential positive ANA serology and arthralgias. Hematologic effects (e.g., neutropenia) and, rarely, hepatotoxicity or seizures may occur. Contraindications include preexisting long QT or torsades risk, significant conduction disturbances, and hypersensitivity. Caution is advised with other QT-prolonging drugs and in patients with autoimmune tendencies. Monitoring of rhythm, blood pressure, electrolytes, and, for long-term use, autoimmune markers is recommended.