Procainamide

It is an amide derivative of the local anaesthetic procaine which was found to have antiarrhythmic activity but was not suitable clinically due to rapid hydrolysis and marked C.N.S. effects. Procainamide is an alternative drug to quinidine, having the same spectrum of efficacy. For i.v. use it is safer than quinidine and has a more rapid action.

Indications

Premature ventricular contractions & tachycardia. Atrial fibrillation. Paroxysmal atrial tachycardia. Cardiac arrhythmias associated with anaesthesia & surgery.

Dosage

For abolition of arrhythmia 0.5-1 gm oral or i.m. followed by 0.25-0.5 g every 2-3 hrs; or 500 mg i.v. loading dose (25 mg/min injection) followed by 2 mg /kg/hour. Maint. 0.5 g every 4-6 hrs. For cardiac arrhythmias associated with anaesthesia & surgery: 0.1-0.5 g i.m. Ventricular extra systoles & tachycardia: 0.2-1 g i.v. Atrial fibrillation & paroxysmal atrial tachycardia 0.5-1g.

Contra-Indications

Systemic lupus erythematosus (SLE), A.V. block.

Special Precautions

myasthenia gravis, donot interact with sulphonamides, renal & hepatic dysfunction, cardiac failure. Paediatrics: Not recommended. Pregnancy: Should be used with cautions. Lactation: Not recommended. Elderly: Use with caution.

Side Effects

Nausea, vomiting, weakness, mental confusion, hallucinations, flushing, hypotension, angioedema, agranulocytosis.

Drug Interactions

Potentiates neuromuscular blocking agents. Impaired action of neostigmine and pyridostigmine. Neutropenia/ Stevens-Johnson syndrome with captopril. Inhibits sulphonamides. Enhances effect of some beta-blockers. Effect enhanced by cimetidine, amiodarone. Alcohol increases elimination.