Source and Composition. Arnica is the plant Arnica montana, the Leopard's Bane, a perennial of the Composite order growing in mountainous districts throughout the northern hemisphere. It contains a principle, Arnicin, which is insoluble in water, and has some of the properties of a glucoside; also about 1 per cent. of an Essential Oil, with Inulin, Tannin, mucilage, resins, Capronic and Caprylic Acids. It also contains Trimethylamine, which is supposed to be the active principle, and to be yielded by the essential oil. Both the Root and Flowers are official.
*Trimethylamine, is an ammonia compound of the group styled amines, in which the three atoms of hydrogen are replaced by some organic radical, in this case by Methyl, (CH3), dissolved in water. It is a clear, colorless fluid, containing 10 to 20 per cent. of the absolute ammonia compound, has a disagreeable, fishy odor and taste, is strongly alkaline, and is miscible in all proportions with water. It is found also in Cod-liver Oil, in Humulus and Ergot, and may be obtained from codeine, fish-brine, human urine, herring-pickle, beet sugar residue, and other decomposing albuminous substances. It behaves like an alkaloid, has strongly basic qualities, and has the formula (CH3)3N, or C3H9N. An impure, commercial trimethylamine is often called Propylamine erroneously, the latter being the name of an isomeric and allied compound.
- Tinctura Arnicae Florum, Tincture of Arnica-flowers,—strength 20 per cent. Dose, ♏v-xxx. For local use, ℥ss to the pint.
- Tinctura Arnicae Radicis, Tincture of Arnica-root,—strength, 10 per cent. Dose, ♏v-xxx. Is locally irritant, unless greatly diluted.
- Extr. Arnicae Radicis Fluidum, Fluid Extr. of Arnica- root,—Dose, ♏v-xx.
- Extractum Arnicae Radicis, Extract of Arnica-root,—Dose, gr. j-iij.
- Emplastrum Arnicae, Arnica Plaster,—has 1/3 of the Extract.
- *Infusum Arnicae Florum, Infusion of Arnica-flowers,—20 parts of the flowers to 100 of water, is thought by some to be the best preparation for local use, as it never excites dermatitis, probably by reason of its being devoid of the Essential Oil and the insoluble principle Arnicin.
- *Trimethylaminae Hydrochloras,—is powerfully antipyretic in doses of gr. ij every three hours. Dose, gr. j-v.
Physiological Action. Arnica is irritant, stimulant, depressant, antipyretic, diuretic, and a vulnerary. It irritates the gastro-intestinal tract, and in alcoholic solution excites erysipelatous inflammation of the skin in some persons. In small doses it increases the action of the heart, raises the arterial tension, and stimulates the action of the skin and kidneys. Large doses produce a transient excitement, followed by depressed circulation, respiration and temperature; violent headache, dilated pupils, and muscular paresis. A Toxic Dose paralyzes the nervous system of animal and organic life, causing collapse and death.
Trimethylamine is an active escharotic, and a gastro-intestinal irritant; lowers the rate and force of the heart, decreases the body temperature, and diminishes (sometimes increases) the excretion of urea.
Therapeutics. Arnica may be used with benefit in—
- Typhus and Typhoid Fevers,—5-minim doses of the Tincture as a stimulant; larger doses as an antipyretic when patient is of sthenic reaction.
- Delirium Tremens with depression,—the Tincture is serviceable.
- Rheumatism and Rheumatic Gout,—Arnica or Trimethylamine in the acute forms, to moderate the fever, subdue the joint inflammation, and lessen the danger of cardiac implication.
- Sprains, Bruises, etc.,—the dilute Tincture locally has a popular reputation. Ecchymoses are rapidly dispersed by its use locally and internally. An infusion is better for local use, as the tincture may excite dermatitis.
- Internal Bruises from shocks or concussions,—its internal use has proven very efficacious in many instances (Phillips).
- Cuts, Wounds, etc.,—the aqueous preparations locally used promote the rapid union of cut surfaces.
- Hemorrhages, Epistaxis, Haemoptysis, etc.,—it is undoubtedly effective.
- Concussion of the Brain,—Arnica is highly recommended (Phillips).
- Chronic Dysentery, with slimy and bloody stools, tormina and cutting pains,—the Tincture internally is often a very efficient remedy.
- Paralysis of the Bladder has been cured by Arnica, used internally.
- Chorea,—Trimethylamine has been successfully used.
- Chronic Rheumatism,—Trimethylamine as a liniment, 1 part to 3 of glycerin, gives relief to the pains, equal to that produced by any anodyne.
A Compend of Materia Medica, Therapeutics, and Prescription Writing, 1902, by Sam'l O. L. Potter, M.D., M.R.C.P.L.