According to the World Health Organization (WHO) the definition of an API is established as any substance or mixture of substances used in a finished pharmaceutical product (FPP), which its ultimate goal is to develop a pharmacological activity or generate some direct effect in the diagnosis, treatment or prevention of a disease in a patient.
APIs are broadly categorized into two types – synthetic and natural. Synthetic APIs are further classified into innovative and generic synthetic APIs, based on the type of synthesis used.