The Collaborative International Dictionary of English v.0.48:

Quinidine \Quin"i*dine\, n. (Chem.)
   An alkaloid isomeric with, and resembling, quinine, found in
   certain species of cinchona, from which it is extracted as a
   bitter white crystalline substance; conchinine. It is used
   somewhat as a febrifuge. [Written also chinidine.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

quinidine
    n 1: cardiac drug (trade names Quinidex and Quinora) used to
         treat certain heart arrhythmias [syn: quinidine,
         Quinidex, Quinora]