Every year an appreciable number of drugs are withdrawn from the market, or their uses are curtailed by black box warnings, due to some adverse effect that was not discovered during preclinical and clinical testing. New assays for mitochondrial function (many of which were developed by MitoSciences) have revealed strong mitochondrial impairment by several previously withdrawn drugs, including cerivastatin (Baycol), troglitazone (Rezulin), nefazodone (Serzone), and tolcapone. Not surprisingly, there is now much more focus on identifying mitochondrial toxicity early in the development process.