noun
Medical term for a drug that blocks or inhibits a biological receptor or physiological response.
この薬はヒスタミン受容体の拮抗薬として作用します。
This drug acts as an antagonist of histamine receptors.
拮抗薬 blocks a receptor or response, while 作動薬 (agonist) activates it.
Compound of 拮抗 (きっこう, 'antagonism, rivalry') and 薬 (やく, 'drug, medicine'). The term is a modern medical coinage.