antagonist

https://doi.org/10.1351/goldbook.A00376
  1. Substance that reverses or reduces the effect induced by an @A00186@.
  2. Substance that attaches to and blocks cell receptors that normally bind naturally occurring substances.
See also:
agonist
Source:
PAC, 1993, 65, 2003. (Glossary for chemists of terms used in toxicology (IUPAC Recommendations 1993)) on page 2014 [Terms] [Paper]