What term describes a drug that inhibits or blocks a neurotransmitter's action?

• A. Antagonist
• B. Agonist
• C. Inhibitor
• D. Blocker

Answer: (A)

A drug that inhibits or blocks a neurotransmitter’s action is called an antagonist. An antagonist binds to the receptor without activating it, or it blocks the receptor so the neurotransmitter can’t bind or can’t trigger the normal response. This prevents the usual postsynaptic signaling and reduces the effect of the neurotransmitter. By contrast, an agonist would activate the receptor and mimic the neurotransmitter’s effect. Terms like inhibitor or blocker are broader and less precise in this receptor-focused context, whereas antagonist is the specific label for preventing receptor activation by a neurotransmitter.