Procainamide Hydrochloride

What it is and how it works

Procainamide blocks fast sodium channels, slowing conduction and prolonging the effective refractory period in atrial and ventricular myocardium and accessory pathways. Its active metabolite N-acetylprocainamide (NAPA) has class III (potassium channel blocking) activity and prolongs the QT interval.

Indications

Treatment of ventricular arrhythmias and of atrial arrhythmias, including pre-excited atrial fibrillation (Wolff–Parkinson–White syndrome), when other agents are unsuitable.

Dosage and administration (summary)

Given by slow intravenous injection or loading infusion (commonly up to 15–17 mg/kg, not exceeding 50 mg/minute, maximum about 1 g) under ECG and blood pressure monitoring, followed if required by a maintenance infusion of 1–4 mg/minute.

Contraindications

Complete heart block or second-degree AV block without a pacemaker, QT prolongation or torsade de pointes, systemic lupus erythematosus and myasthenia gravis.

Warnings and precautions

Stop the infusion if hypotension occurs, QRS widens by more than 50% or QT prolongs excessively; reduce dose in renal or heart failure. Long-term use may cause drug-induced lupus and, rarely, agranulocytosis.

Storage and supply

Store below 25 °C; do not use if the solution is darker than light amber.

Source: reference summary prepared from the EU SmPC/EPAR, BNF and WHO Model Formulary. The approved product information in Iran governs.