Doxorubicin is a very effective anti-cancer drug that causes congestive heart failure while treating tumors. Doxorubicin is an uncoupling agent in that it inhibits proper functioning of complex I of the electron transport chain in mitochondria. It then leads to the production of ROS and the inhibition of ATP production. Doxorubicin has been shown to be selectively toxic to cardiac tissue, although some toxicity has been seen in other tissues as well. Other anti-cancer drugs, such as fluoropyrimidines and taxanes, are extremely effective at treating and reducing tumor proliferation, but have high incidences of cardiac arrhythmias and myocardial infarctions.