Which class of drugs has receptor interaction intensity less than endogenous dopamine?

• A. Full dopamine agonists
• B. Partial dopamine agonists
• C. Antagonists
• D. Inverse agonists

Answer: (B)

Endogenous dopamine acts as a full agonist at dopamine receptors, producing the maximum possible receptor response. A drug that has less intrinsic activity at the same receptor—binding but only triggering a submaximal response—is a partial agonist. It can't elicit the full effect of dopamine, so its activation is weaker even when it occupies all available receptors. In practice, partial agonists can dampen dopamine signaling in high-dopamine conditions by competing with dopamine, yet provide some activation when dopamine levels are low. Full agonists would match or exceed dopamine’s effect, antagonists would produce no activation, and inverse agonists would reduce baseline receptor activity. Hence, the class with receptor interaction intensity less than endogenous dopamine is partial dopamine agonists.