An active ingredient, also active pharmaceutical ingredient (or API), is the substance in a drug that is pharmaceutically active. The traditional word for the API is pharmacon (from Greek: (φάρμακον), adapted from pharmacos) which originally denoted a magical substance or drug.

A capsule, tablet, syrup, intravenous fluid, or any other formulation of a drug is traditionally composed of two things: The API, which is the drug itself; and an excipient, which is the substance of the tablet, or the liquid the API is suspended in, or other material that is pharmaceutically inert.

See also

• Pharmakos
• counterfeit drug

Pharmacology

Arzneistoff | Principe actif