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.

What does a partial agonist do?

Partial agonists bind to and activate a receptor, but are not able to elicit the maximum possible response that is produced by full agonists. ... A key property of partial agonists is that they display both agonistic and antagonistic effects.

What is a full and partial agonist?

A full agonist has high efficacy, producing a full response while occupying a relatively low proportion of receptors. A partial agonist has lower efficacy than a full agonist.