According to the FDA, generic drugs are required to have the same active ingredient, strength, dosage form, and route of administration as the original brand-name drug. All manufacturing, packaging, and testing sites must also pass the same quality standards as the brand-name drug.
The Supreme Court has determined that generic drug makers are not liable for any negative side effects; the original manufacturer is. (See PLIVA, Inc. v. Mensing, 564 U.S. 604 and Mutual Pharmaceutical Co. v. Bartless, 570 U.S. 2468.)