QUINIDINE

alkaloid found in cinchona bark and used as a drug. It shares many of the pharmacological actions of quinine; i.e., both have antimalarial and fever-reducing activity. The main use of quinidine, however, involves its activity as a myocardial depressantthat is, it depresses the excitability and conduction velocity of nerve impulses and the contractility of the heart muscle. Quinidine is thus used to treat a variety of disorders of cardiac rhythme.g., atrial fibrillation, atrial flutter, and ventricular tachycardia. It can be a dangerous drug and is used less frequently than digitalis. Nausea, vomiting, and diarrhea are common reactions to the use of quinidine.