We do not currently know of any antonyms for atropine.
The noun atropine is defined as:
An alkaloid extracted from the plant deadly nightshade (Atropa belladonna) and other sources. Though overdoses would be fatal it is used as a drug in medicine for its paralytic effects (e.g. in surgery to relax muscles, in dentistry to dry the mouth, in ophthalmology to dilate the pupils).