Which of the following is an example of a drug action that does not involve receptors?

• A. Chelating agents forming complexes with metals
• B. Receptor blockade
• C. Allosteric modulation
• D. Agonist-activated signaling

Answer: (A)

Some drugs act without involving receptors; their effects come from direct chemical interactions rather than binding to a receptor. Chelating agents are a clear example: they form stable complexes with metal ions, effectively removing them from biological processes. This changes the chemical environment and function without triggering or blocking any receptor and without initiating receptor-mediated signaling. In contrast, receptor blockade, allosteric modulation, and agonist-activated signaling all require interaction with a receptor—either blocking it, changing its activity from an alternate site, or activating it to start intracellular signals. That receptor-independent chemical sequestration is what makes chelating agents the correct example.