Source and Composition. It is an active toxic alkaloid of syrupy consistence, from Agaricus muscarius, (Amanita muscaria), the fly-agaric, a poisonous mushroom, used in Kamschatka as an intoxicant. The alkaloid is freely dissolved out by water and dilute acetic acid, so that a doubtful fungus may be easily rendered innocuous. Its formula is C5H15NO3.
- *Muscarina, Muscarine,—Dose, gr. 1/8-ij.
- *Muscarinae Nitras, Dose, gr. 1/8-ij.
Physiological Action. Muscarine is a powerful respiratory and cardiac depressant, paralyzing the respiratory centre, and arresting the heart in diastole by paralyzing the cardiac muscle while stimulating its inhibitory apparatus. It lowers the arterial tension, produces profuse salivation and sweating; contracts the pulmonary vessels, causing intense dyspnoea; and increases the intestinal, hepatic and pancreatic secretions, but markedly diminishes the renal. It disturbs the gastro- intestinal tract, causing severe colic, vomiting and purging. It produces spasm of the accommodation, and marked myosis, contracting the pupil when given internally, but dilating the pupil widely when locally applied. (Gelsemium does so also.) Under its action the body temperature is decidedly reduced, and the excretion of waste-products lessened. On the cerebrum Agaricus acts as an intoxicant, producing more vertigo and delirium than Alcohol, followed by profound sopor with lowered reflexes, perhaps coma and death.
Antagonist. Atropine exactly opposes Muscarine, and vice versa; no example of physiological antagonism being so complete in all particulars. When a frog's heart is arrested by the topical action of a minute quantity of Muscarine, the application of a little Atropine will immediately restore the pulsations (Ringer). An equally prompt antagonism runs through their entire spheres of action.
Therapeutics. Clinical experience with Muscarine, is wanting. It has been used with considerable benefit in—
- Night-sweats of Phthisis,—in which it is found extremely efficient.
- Chorea,—Agaricus has proven a potent remedy in the idiopathic form.
- Ataxic Typhus, with great restlessness and tremor, a tincture of Agaricus in drop doses has often been effectively employed.
- Chilblains,—have been cured by the same preparation, locally applied.
- Inflammations characterized by copious exudation,—Muscarine promises to be of great service, especially in Eye Inflammations with exudation,—as it permits of the contraction or dilatation of the pupil at will, according as it is used internally or locally.
- Constipation due to torpor of the intestines and deficient secretion, accompanied by a torpid liver and difficult digestion of fats,—Muscarine is exactly indicated in doses of gr. 1/30 thrice daily.
- Catarrhal jaundice, and Diabetes of both forms,—are conditions in which Muscarine promises to be of especial service.
A Compend of Materia Medica, Therapeutics, and Prescription Writing, 1902, by Sam'l O. L. Potter, M.D., M.R.C.P.L.