Anti Arrhythmic Drug

In a normal person the heart functions in a rhythmic manner . In heart disease or due to toxic effect of some drugs this normal rhythm is disturbed and this condition is generally called arrhythmia . Arrhythmias could be due to a defect in the impulse generation or due to defect in the impulse generation or due to abnormal propagation of impulse . Antiarrhythmic drugs are used to correct cardiac arrhythmias . Antifibrillatory drugs are compounds which prevent the development of atrial or ventricular fibrillation .

Anti-arrhymic agents are divided boardly into two categories .

1.       That act on ventricular arrhythmias like ligocaine

2.       That act on supraventricular arrhythmias like verapamil .

According to the mode of action anti-arrhythmic agents are classified as .

1.       Includes drugs which directly interfere depolarization of the cardiac membrane by blocking the fast inward current of sodium into cardiac cells , they also have local anaesthetic properties like ligocaine .

2.       Includes drugs with antisympathetic properties like propranolol and bretylium

3.       Include drugs that prolong the duration of the cardiac action potential like amidodarone

4.       Include drugs that block the slow inward calcium current like verapamil .

Quinidine and proëainamide are the most effective drugs to treat cardiac rate and rhythm. Some other drugs are procaine quinacrine, quinine, papaverine, digitalis preparation, etc

Quinidine (Brand Names: Pitayine; p-guinine), m.p. 174-175, is a dextrorotatory stereoisomer of quinine present in cinchona bark to the extent of O.25-3.0%. The molecule contains two nitrogens - the side chain nitrogen is more basic. It forms two series of salts.

Quinidine Sulphate (Brand Names : Quinidine bisulphate, Kiditard; Kinichron; Kinidin; Kinidrin; Quiniduran). This salt crystallizes from water as the dihydrate to yield needle-like, white crystals. It has bitter taste and .ܶ darkens on exposure to light. It is slightly soluble in water; soluble in boiling water, alcohol and chloroform; practically insoluble in acetone and the ether. It is stored in well-closed containers and protected from light.

Commercial quinidine sulphate may contain up to 20 per cent of dihydroquinidine sulphate, which has a greater antifibrillating action than quinidine, but is more toxic.

Quinidine Gluconate (Brand Names : Gluconic acid quinidine salt; Duraquin; Dura-Tab; Gluquinate; Quinaglute), m.p. 175177, is a white odourless powder. It is freely soluble in water; slightly soluble in alcohol. The aqueous solutions are stable. It is protected from light.

Quinidine Polygalacturonate (Brand Names : Cardioquin; Galactoquin; Naticardina; Sineflutter), m.p. 180° (decomp), is an amorphous powder. This is produced by reacting quinidine and polygalacturonic acid in a hydroalcoholic medium. It contains the equivalent of nearly 60 per cent quinidine. Anhydrous product is insoluble in methanol, alcohol, chloroform, ether, acetone, dioxane; soluble in 40% methanol or ethanol; 12% in water at 25°. It affords controlled and more uniform absorption through the mucosa than quinidine sulphate.

Uses : Quinidine is an anti-arrhythmic agent. It also has antimuscarinic and alpha-adrenergic blocking properties.

Quinidine and its salts cause both cardiac and extracardiaeadverse effects. They commonly cause gastro-intestinal irritation with nausea, vomiting and diarrhoea. Other side effects are cinchonism, tinnitus, impaired hearing, visual disturbances, headache, confusion, vertigo, and hypotension.