Antidote, AN tee doht or AN tih doht, is a substance that fights the harmful action of a poison in the body. Some antidotes act chemically on poisons to make them harmless. Other antidotes produce an action that works against the action of the poison. Still other antidotes can prevent certain body cells from reacting to the effects of a poison. Antitoxins are a special kind of antidote (see Antitoxin).