Partial agonist

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In pharmacology, partial agonists are drugs that bind to 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.[1] Clinically, partial agonists can be used to 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.[2]

Some currently common drugs that have been classed as partial agonists at particular receptors include buspirone, aripiprazole, buprenorphine, and norclozapine.

See also[edit]


  1. ^ N. E. Williams and T. N. Calvey (2001). Principles and Practice of Pharmacology for Anaesthetists. Blackwell Publishing. ISBN 0-632-05605-3
  2. ^ Zhu BT (2005). "Mechanistic explanation for the unique pharmacologic properties of receptor partial agonists". Biomed. Pharmacother. 59 (3): 76–89. doi:10.1016/j.biopha.2005.01.010. PMID 15795100.