Quinidine

Drug used in the treatment of abnormal heart rhythms (arrhythmia) and malaria. Obtained from the bark of the Cinchona tree, quinidine 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 depressant—that is, it depresses the excitability