Drugs Withdrawn From Market, January 2001, Letter from US General Accounting Office,

The Food and Drug Administration (FDA) approves drugs for sale in the United States based on its determination that the clinical benefits of a drug outweigh its potential health risks. To make this decision, FDA reviews supporting data collected from several thousand patients during the drug’s development. Once a drug is approved for marketing and used by potentially hundreds of thousands of patients, however, the type , rate, and severity of adverse events caused by the drug can be much different than those detected during the drug’s development. In some cases, FDA or drug manufacturers have acted to remove from the market drugs that have been shown to have unacceptable health risks once they were in widespread use.