Eserine, well-known as physostigmine, is classified as an alkaloid. It is a cholinesterase inhibitor and appears in Agatha Christie's novel entitled, Crooked House and Curtain: Poirot's Last Case. In clinical medicine, eserine was used as an ophthalmic treatment for glaucoma and considered as a treatment for myasthenia gravis, Alzheimer's disease, and hereditary cerebellar ataxias. Currently, it is used as a treatment for anticholinergic poisoning.