Ultrastructural changes in the heart of rats treated with chloroquine.

Effects of prolonged chloroquine administration on ultrastructure of the heart was studied in albino rats. Chloroquine when administered orally (30-40 mg/kg/day) or subcutaneously (20 mg/kg/day) for two to four weeks, produced marked degenerative changes in the mitochondria and myofibrils of the myocardium. The mitochondria were more susceptible to the toxic effect of chloroquine than were other cell organelles. Moreover, the cytotoxic effect of the drug appeared to be related to total dose. Chloroquine-induced abnormalities were reversible on terminating medication. These results indicate that prolonged chloroquine administration impairs ultrastructure of the myocardium.