Source and Composition. The seeds of Physostigma venenosum, (nat. ord. Leguminosae), a woody creeper of Calabar, West Africa, where it is used by the natives as an ordeal for witches, etc. It contains an alkaloid, which is variously named Eserine, Calabarine and Physostigmine,—also albuminous matters, starch and oil.
- Extractum Physostigmatis,—alcoholic. Dose, gr. 1/6-j.
- Tinctura Physostigmatis,—15 per cent. Dose, ♏v-xx.
- Physostigminae Salicylas,—Physostigmine (Eserine) Salicylate,—bitter crystals, soluble in 150 of water and in 12 of alcohol. Dose, gr. 1/100-1/60.
- Physostigminae Sulphas,—Physostigmine (Eserine) Sulphate,—a bitter powder, deliquescent, soluble in water and in alcohol. Dose, gr. 1/100-1/50.
- *Lamellae Physostigminae,—Disks of Physostigmine (B. P.),—Medicated disks, used locally on the eye, each containing gr. 1/1000.
Physiological Action. Physostigma is a muscular stimulant and a direct spinal paralyzer, producing complete general paralysis, and abolishment of the reflexes, but does not affect muscular irritability or the brain. It stimulates secretion, excites nausea and vomiting; and is laxative by stimulating the muscular coat of the intestines, as well as by increasing the intestinal secretions. It first lowers, then raises the arterial tension; increases the heartbeat in frequency, but depresses the power of the cardiac muscle, though not destroying it. It produces dyspnoea by a tetanic action on the respiratory muscles, causing CO. poisoning, and death by paralysis of respiration. It contracts the pupils (how, is disputed) and the ciliary muscle, producing marked myosis. It is eliminated chiefly by the kidneys, the urine of the animal affected poisoning another.
Antagonists. Atropine as to the respiration, heart and pupil. Chloral is also antagonistic, but to be effective must be administered some time before the ingestion of the Physostigma.
Therapeutics. Physostigma has but a small field of action. In—
- Constipation, due to torpor of the bowels,—combined with Belladonna and Nux Vomica, it is sometimes very effective.
- Tetanus,—it has been used with great advantage to diminish reflex excitability; grain doses of the extract repeated every two hours.
- Progressive Paralysis of the insane-this drug seems to retard it.
- Strychnine and Atropine Poisoning,—Physostigma is antagonistic.
- Eye Diseases, Physostigmine (Eserine) is now used by ophthalmologists for almost every indication, just as a few years ago they used its exact antagonist-Atropine. It is useful to break up or prevent adhesions of the iris, to relieve tension, to prevent suppuration after operations, as well as to contract the pupil and the vessels of the eye, thereby relieving pain and photophobia.
A Compend of Materia Medica, Therapeutics, and Prescription Writing, 1902, by Sam'l O. L. Potter, M.D., M.R.C.P.L.