An antidote is a remedy or treatment for a disease or poison. However, there are several antonyms for this word, which include "poison," "venom," "toxin," "noxious substance," "danger," and "hazard." These are all the opposite of the definition of an antidote, as they all bring harm or danger to a person's health. In addition to these, there are other related antonyms such as "illness," "infection," "disease," "ailment," "condition," and "disorder." All of these words are associated with sickness and poor health, which are the exact opposite of what an antidote is designed to provide.