Generic medicines must be both safe and effective in order to be approved by the FDA. The FDA also requires generics to meet the same requirements for strength, purity, and quality as the original manufacturer.
Generic manufacturers must prove that their version of the brand-name drug contains the same active pharmaceutical ingredient, is identical in dosage form, route of administration, and strength. The generic version must also have the same indications, dosing, labeling, and provide the same efficacy and safety profile as the brand.
Generic manufacturers do not need to repeat the clinical (human) or animal studies that are required for the original manufacturer. The reduced upfront costs allow generic medicines to be sold for considerably less than their branded counterparts. Additionally, there are typically multiple approved generic drugs, which creates competition, ultimately lowering the selling price of a generic medicine.