Geneesmiddel-Receptor Interactie: Antagonist

An antagonist is a drug that strongly binds a receptor but does not activate it. Although it produces no effect by itself, it prevents the receptor from interacting with agonists or endogenous ligands, which blocks or reduces their effect.

Based on antagonist-receptor interaction, antagonists can be competitive or noncompetitive.

A competitive antagonist competes with an agonist to bind the receptor at the same site, stabilizing the receptor's inactive state. In a plot of agonist concentration versus response, an antagonist shifts the curve towards the right as it reduces the number of available receptors. Increasing antagonist concentration further reduces receptor availability, diminishing the effect of the agonist.

Such receptor-antagonist interactions are reversible. Increasing agonist concentration reverses the antagonist's effect by restoring agonist-receptor binding.

A noncompetitive antagonist binds covalently to the receptor's active site and prevents agonist binding. Even increasing the concentration of agonists cannot displace these antagonists from the receptor. Such irreversible antagonists lower the maximal effect of the agonist, reducing agonist efficacy.