Compound Type
Excipient
Last updated
A substance present in a formulation for a reason other than its own biological effect: to stabilise the active ingredient, to hold the pH steady, to bulk out a freeze-dried cake, or to hold back microbial growth. Mannitol, benzyl alcohol, metacresol and phosphate buffers are typical. The type exists so that ingredients read off a label are not mistaken for active compounds in their own right.
Why it matters here
Excipients are where several real problems live: a preservative someone reacts to, a buffer that governs how long a reconstituted vial holds, or a bulking agent that makes a small quantity of powder look like a full vial.
What it is not
Inactive means not intended to act, not incapable of acting, and excipients account for a meaningful share of injection-site reactions. An excipient is also not a vehicle: the vehicle is the liquid added at reconstitution, while the excipient was already in the vial when it was sealed.
Also called
- excipient
- inactive ingredient
- stabilizer
Inactive ingredient is the regulatory phrase used on packaging. It describes intent rather than biological inertness.
Compounds carrying this term
None on file yet. This term is in the controlled vocabulary but no compound record currently uses it — which is a statement about our coverage, not about the term.