A substance that counteracts a poison. Used in medical, toxicological, and figurative contexts.
I was bitten by a snake, so I was given an antidote injection right away.
この薬は特定の毒に対する解毒剤として使われる。
This medicine is used as an antidote for a specific poison.
毒消し is a more colloquial term for something that counteracts poison, often used in folk remedies or everyday speech, whereas 解毒剤 is the formal medical term.
解毒剤 is an antidote that neutralizes poison, the functional opposite of 毒薬 which causes harm.
Compound of 解毒 (detoxification) + 剤 (agent, medicine).