To block receptors, what must a drug possess?

• A. Binds strongly and acts as an agonist capable of full receptor activation.
• B. They must bind effectively, but have little to no intrinsic activity
• C. They must be highly selective for multiple receptor types.
• D. They must be rapidly metabolized before reaching the receptor.

Answer: (B)

To block a receptor, a drug must sit in the binding site with high affinity but have little to no intrinsic activity. This means it can occupy the receptor so endogenous ligands or other agonists can’t activate it, but it won’t trigger any signaling on its own. If the drug activated the receptor, it would function as an agonist and produce a response rather than block it. If it were rapidly metabolized before reaching the receptor, it wouldn’t achieve the necessary occupancy to block signaling. So the essential property is strong binding coupled with minimal or no activation of the receptor.