The Food and Drug Administration (FDA) is making encouraging moves to strengthen its regulation of drugs that are already on the market. But the changes fall far short of what’s needed to protect millions of unsuspecting patients whose adverse effects may show up only after years of use. The agency has traditionally focused on the drug-approval process to determine if a drug is safe and effective. Unfortunately, by that time a drug has typically been tested in only a few hundred or a few thousand patients – too few for many kinds of adverse effects to become apparent. Once the drug is being used by millions, the agency has limited powers to halt sales that begin to look risky.