Atropa belladonna
Furthermore, a reputable publication by the former UK Ministry of Agriculture, Food and Fisheries (now DEFRA) states specifically that, in cases of poisoning by "Atropa belladonna" - far from being antidotes - 'Preparations containing morphine or opiates should be "avoided" as they have a synergic action with atropine'; an appropriate antidote being, by contrast, the acetylcholinesterase inhibitor physostigmine salicylate.