What does it mean for a receptor-drug interaction to be reversible?

• A. The receptor remains permanently blocked
• B. After a while, the drug disengages from the receptor and it resumes normal function
• C. The drug is covalently bound
• D. The receptor is degraded

Answer: (B)

Reversibility means the drug can detach from the receptor and the receptor can return to signaling once the drug leaves. When binding is reversible, the interaction is non-covalent, so the complex can form and break at a rate set by affinity and the off-rate. As the drug dissociates (or is cleared), fewer receptors stay occupied, and normal function resumes. This is in contrast to irreversible scenarios, where covalent binding would leave the receptor blocked long-term, or receptor loss/degradation, which reduces receptor numbers rather than simply stopping a reversible interaction. So the statement that the drug disengages from the receptor and the receptor resumes normal function best describes reversibility.