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.
This medicine is used as an antidote for a specific poison.
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).