This section is from the book "Botanic Drugs Their Materia Medica, Pharmacology and Therapeutics", by Thomas S. Blair. Also available from Amazon: Botanic Drugs, Their Materia Medica, Pharmacology and Therapeutics.
Calabar Bean, Physostigma venenosum. Official in Belgium, Japan, Mexico, Spain, and the U. S.
Resembles that of pilocarpine and muscarine. Physostigmine, or Eserine, the principal alkaloid, by application to the conjunctiva, contracts the pupil; it is the opposite or antagonist of atropine. Causes a fall in intraocular tension.
Physostigmine has slight inhibitory action on the heart. Stimulates secretion of saliva and sweat, but less than does pilocarpine. Definite stimulant action on the muscular walls of the stomach, intestines, and bladder. Induces constriction of the bronchioles. Causes tremulous twitching of striped muscle and depresses the central nervous system. Toxic doses cause respiratory paralysis. The antidote is atropine.
Has been used as a hypodermic purgative, but it is apt to occasion vomiting and severe griping. In post-operative paralytic distention of the bowel it has been superseded by pituitrin and similar hypophyseal extracts. The former uses in tetanus, epilepsy, chorea, locomotor ataxia, etc., while theoretically justified, do not work out well clinically.
Eserine, in the form of the salicylate and sulphate, is used in ophthalmic practice (0.25 to 1% sol.) after atropinisation and to reduce intraocular tension, as in glaucoma. The alkaloid in oil, as well as Lamellae Physostigminae (B. P.), are similarly used. The lamellae contain 1-1000 grain each.
Physostigma, 1 1/2 grains; salts of the alkaloids, 1-60 grain; extract, 1-8 grain; tincture, 15 minims. Fl, 1 to 2 minims.