Glossary of Pharmacology 

Reversible antagonist

An antagonist that binds to the receptor in a reversible manner. The interaction between the antagonist and the receptor is not covalent and therefore the antagonism is surmountable at a certain concentration of the agonist.  

Example:

Phentolamine is an antagonist of the α-adrenergic receptors in the blood vessels, and it reversibly blocks the vasoconstrictive action of catecholamines leading to dilation of the blood vessels and reduction in blood pressure.  

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