Quinidine

It is an alkaloid from Cinchona bark-the dextroisomer of quinine & has been noted to suppress ‘rebellious palpitation.’ Quinidine increases threshold for excitation and reduces conduction velocity, thus limits the spread of arrhythmia.

Indications

Atrial fibrillation or flutter, paroxysmal supra ventricular tachycardia. Ventricular premature beats & ventricular tachycardia. Maintenance of sinus rhythm following electro conversion.

Dosage

200-300 mg 3-4 times daily. Initially give test dose.

Contra-Indications

Not recommended for children. Myasthenia gravis. Intolerance or idiosyncrasy to quinidine, heart block, C.H.F. and hypotensive states. History of embolism.

Special Precautions

Renal dysfunctions. Paediatric: Not recommended. Pregnancy: No serious effect reported. Lactation: Not recommended. Elderly: Reduced dosage necessary.

Side Effects

Higher doses can cause A.V. dissociation, nausea, vomiting, diarrhoea, cinchonism (ringing in ear, deafness, vertigo, headache, visual disturbances), angioedema, asthma & vascular collapse.

Drug Interactions

Cimetidine, erythromycin inhibits the hepatic metabolism of quinidine, interaction with beta-blockers causes sinus bradycardia. Amiodarone may increase the plasma concentration of quinidine. Phenobarbitone and rifampicin decreases its effects. Hyperkalemia increases effect of quinidine.