The active pharmaceutical ingredient (API) is the part of any drug that produces the intended effects. Some drugs, such as combination therapies, have multiple active ingredients to treat different symptoms or act in different ways.
All drugs are made up of two core components—the API, which is the central ingredient, and the excipient, the substances other than the drug that help deliver the medication to your system. Excipients are chemically inactive substances, such as lactose or mineral oil in the pill.