Active pharmaceutical ingredients (APIs) are the active components in a pharmaceutical drug that produce the required effect on the body to treat a condition. APIs are produced by processing chemical compounds. In a biologic drug, the active ingredient is known as a bulk process intermediate (BPI).

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.

Synthetic chemical APIs, also known as small molecules, constitute a large part of the pharmaceutical market, with many small molecule drugs commercially available in the market.

Natural APIs are used in making biologics, which are increasingly becoming the top-selling drugs in the market. Despite the growing demand, biologics are currently significantly fewer in number compared to small molecule drugs.

Based on the solubility, APIs are categorized into insoluble and soluble drugs.

Pharmaceutical intermediates are chemical compounds which form the building blocks of active pharmaceutical ingredients (APIs). Pharmaceutical intermediates are produced as by-products during the production of an active pharmaceutical ingredient (API).

Both active pharmaceutical ingredients (APIs) and intermediates belong to the category of fine chemicals. The main difference between the two is that the active pharmaceutical ingredient (API) is an active product that has been completely synthesized, and the intermediate is a product at a certain place in the synthesis route.

While active pharmaceutical ingredients (APIs) exhibit pharmacological activity or other direct effects in the diagnosis, treatment, symptom relief, or prevention of diseases, intermediates are materials produced during the synthesis of APIs, which can only be turned into API by further molecular change or refinement.

Pharmaceutical intermediates, veterinary drug intermediates, and bulk drug intermediates are various types of drug intermediates. Drug intermediates are hygienically formulated using high-grade raw materials and they are used in the pharmaceutical industry. Pharmaceutical intermediates are also used for research and development purposes by pharmaceutical and biopharma companies.