Contamination with - or excessive exposure to - certain chemicals including: nerve agents, (e.g. sarin, VX, Novichok agents). organophosphorus insecticides (e.g. parathion) nicotine poisoning can also present with similar symptoms, as it also involves excessive parasympathetic stimulation.[3] Ingestion of certain poisonous fungi (particularly the muscarine-containing members of the genera Amanita, Inocybe and Clitocybe). In medicine, this is seen in patients with myasthenia gravis who take too high a dose of medications such as cholinesterase inhibitors, or seen following general anaesthesia, when too high a dose of a cholinesterase inhibitor drug is given to reverse surgical muscle paralysis.