Which term describes a drug that binds to receptors and mimics the effects of endogenous compounds?

• A. Agonist
• B. Antagonist
• C. Partial agonist
• D. Inverse agonist

Answer: (A)

A drug that binds to a receptor and produces a response by mimicking the body's own ligands is an agonist. Agonists activate receptors, so they reproduce the effect that endogenous compounds like neurotransmitters or hormones would normally cause. The strength of the response depends on efficacy: a full agonist can produce the maximum possible effect when receptors are occupied, while a partial agonist yields only a partial response even at full occupancy. This is different from antagonists, which bind without activating and block the receptor, and inverse agonists, which reduce any baseline activity the receptor may have. So, the term describing a drug that mimics endogenous compounds by activating receptors is agonist.