Acting as a means of warding off disease; acting as a remedy; prophylactic.

Having the power of warding off the effects of poison taken inwardly; antidotal.

noun. An antidote to poison or infection, especially an internal antidote.

adjective. Expelling or counteracting poison; antidotal.

noun. An antidote against poison or infection; a counterpoison.

noun. An antidote to poison.

adjective. Acting against poison.

"The medicine mithridate forms a part of many of these prescriptions; it does not seem to be regarded as an alexipharmic, but as a soporific."

alexipharmical  

antidotal  counterpoison