A drug that binds to a receptor at a site distinct from the active site (allosteric or non-agonist site) and reduces the affinity of the receptor for the endogenous ligand is termed as allosteric inhibitor. Allosteric inhibition is a form of non-competitive antagonism (Allosteric antagonism). Allosteric Modulator: An allosteric modulator is a drug that binds to a receptor at a site distinct from the active site and induces a conformational change in the receptor, which alters the affinity of the receptor for the endogenous ligand. Positive allosteric modulators increase the affinity, whilst negative allosteric modulators decrease the affinity. Ref: Katzung 14th edition Pgno: 24