Glossary of Pharmacology 

Non-Competitive antagonist

An antagonist that prevents the biological response of an agonist without competing with the agonist on the same binding site on the receptor. The antagonist binds to a distinct site on the receptor and therefore the agonist can still bind to the receptor but cannot elicit a biological response. 

Example:

Ketamine is antagonist of N-methyl-D-aspartate (NMDA) receptor, a member of the glutamate receptors in the CNS. It exerts its anesthetic and analgesic effect by interacting with the receptor on a binding site different than glutamate. 

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