The Active Pharmaceutical Ingredient (API) is the part of any drug that produces its effects. Some drugs, such as combination therapies, have multiple active ingredients to treat different symptoms or act in different ways.
Production of APIs has traditionally been done by the pharmaceutical companies themselves in their home countries. But in recent years many corporations have opted to send manufacturing overseas to cut costs.
This has caused significant changes to how these drugs are regulated, with more rigorous guidelines and inspections put into place.