From Pixelmon Wiki
An Antidote is a type of medicine used to heal Pokémon from the poisoned and badly poisoned statuses. Before Pixelmon Reforged, it could be crafted using the following recipes. It can be obtained from shopkeepers and as a tier 1 special drop. It cannot be crafted anymore.
Trivia
Antidotes used to have the following crafting recipes, which are no longer working.
Antidotes could also be used to craft Full Heals. This recipe is no longer working.