Active pharmaceutical ingredient (revision 5)

An active pharmaceutical ingredient (API) is a substance intended to be used in the manufacture of a medicinal product and to furnish pharmacological activity in it. The term is a regulatory category rather than a chemical one: the same molecule is an API when destined for a medicine and is not when destined for laboratory research.^[1]

That distinction determines which requirements apply. API manufacture is subject to GMP and to registration in many jurisdictions; the same chemistry performed for research supply is not.^[1]

The practical consequence is that "pharmaceutical grade" applied to a research chemical is not a defined term. Where it means anything, it means the supplier's own grade designation, and what it covers is whatever the accompanying specification says.^[2]

Guidance for APIs covers the same ground as finished-product GMP, adapted to bulk substance: materials, process controls, validation, records, and the point in a process at which GMP begins to apply — which for a synthetic API is generally the introduction of the starting material into the process.^[1]

Registration mechanisms vary. A drug master file allows a manufacturer to submit confidential process detail to a regulator and to authorise a customer to reference it; other jurisdictions use certificates of suitability or direct registration.