Non-competitive inhibition

As a non-competitive antagonist of a substance is referred to pharmacology, and biochemistry, which is able to inhibit the binding of an agonist to a receptor, without the substance can be expelled by the agonist. Non-competitive antagonists bind to a different ( allosteric ) binding site as the agonist to the receptor. Also, inhibitors of signal transduction behave as non-competitive antagonists. Substances which bind irreversibly to the receptor, can also exhibit a non-competitive antagonism.

An example is the active ingredient of ketamine, which is not blocked on the NMDA receptor binding site for the physiological agonists glutamate, but the channel pore itself dose-response curves and the EC50 of the position will change accordingly.