In order to win FDA approval, generic drugs must demonstrate bioequivalence, namely the ability to achieve blood levels similar to those of the innovator ones on which they are based. They must have the same active ingredients, be identical in strength, dosage form, and route of administration, and be manufactured under strict FDA standards. Because basic efficacy and safety studies are not required, their cost is significantly lower. However, there can be important differences between the innovator drugs and generics, as well as among the generics themselves. More research needs to be done to establish true comparability.