IPA: /ˌæn.tɪˈdoʊ.təl/
KK: /ˌæntɪˈdoʊtəl/
Related to a substance that counteracts a poison or disease.
The doctor provided an antidotal treatment to counteract the effects of the venom.
Antidotal is formed from "anti-" (meaning against) and "dote" (from Latin "dote", meaning to give or bestow). The word refers to something that counteracts or works against a poison or disease, hence an antidote.
Think of 'anti-' meaning against, and 'dote' meaning to give — an antidote is something that gives protection against poison.
No commonly confused words.