Physostigmine

PHYSOSTIGMINE (eserine), an alkaloid, the active principle of the calabar bean, Physostigma venenosum Balfour (family Papilionaceae), growing in Africa. One of the most poisonous alkaloids.

As a result of this, the calabar bean was used by indigenous peoples for the so-called "divine judgment" (owing to the presence of an emetic substance in the plant, some avoided death in case of poisoning). It is used in the form of the salicylic acid salt. A colorless or slightly yellowish crystalline powder, sparingly soluble in water. The aqueous solution is unstable and rapidly turns red due to the formation of rubroeserine. In veterinary practice, the sulfuric acid salt of physostigmine is also used, forming crystals that deliquesce easily in air and are readily soluble in water. It belongs to the series of parasympathetic stimulants, like choline, muscarine, pilocarpine. In the central nervous system, physostigmine causes excitation, rapidly replaced by paralysis. Physostigmine exerts an excitatory effect on smooth musculature, increasing its excitability (Kravkov), and on striated musculature (through nerve endings), acting as an antagonist of curare. The pupils are sharply narrowed as a result of this (contracture of the sphincter of the iris and ciliary musculature). At the same time, a disturbance of accommodation occurs, usually passing considerably earlier than the constriction of the pupil. Simultaneously with the pupillary constriction, intraocular pressure decreases. Heart contractions become stronger and slower, and blood pressure rises; with toxic doses, collapse ensues (central action). It is used in eye practice for glaucoma, paresis of the ciliary muscles, and synechiae. Dose: two to three drops of a ¼–1⅓% solution of Physostigmini (Eserini) salicylici. For intestinal atony (postoperative intestinal paralysis), flatulence. Doses: subcutaneously ½–1 mg 1–2 times a day and internally. Its use is limited, as collapse and respiratory paralysis are frequently observed after physostigmine. Physostigmine is excreted partly in the urine; traces of it are found in saliva and bile; the greater part of physostigmine is destroyed in the organism.

B. Voskresensky.