Antimonials, in pre-modern medicine, were remedies principally containing antimony, used chiefly for emetic purposes. They might also have qualified for cathartic, diaphoretic, or simply alternative uses. Such treatments were considered unparalleled in their strength.
Metaphorical usage
The following passage illustrates the use of the word antimonial to mean emetic in common (as well as medical) terms:
References
Antimonial Wikipedia(Text) CC BY-SA