Partial agonist

Partial agonists (such as buspirone, aripiprazole, buprenorphine, or norclozapine) also bind and activate a given receptor, but have only partial efficacy at the receptor relative to a full agonist. They may also be considered ligands which display both agonistic and antagonistic effects - when both a full agonist and partial agonist are present, the partial agonist actually acts as a competitive antagonist, competing with the full agonist for receptor occupancy and producing a net decrease in the receptor activation observed with the full agonist alone. [Principles and Practice of Pharmacology for Anaesthetists By Norton Elwy Williams, Thomas Norman Calvey Published 2001 Blackwell Publishing ISBN 0632056053] Clinically partial agonists can activate receptors to give a desired submaximal response when inadequate amounts of the endogenous ligand are present, or they can reduce the overstimulation of receptors when excess amounts of the endogenous ligand are present. [cite journal |author=Zhu BT |title=Mechanistic explanation for the unique pharmacologic properties of receptor partial agonists |journal=Biomed. Pharmacother. |volume=59 |issue=3 |pages=76–89 |year=2005 |pmid=15795100 |doi=10.1016/j.biopha.2005.01.010]

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