This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
On comparing arnica with other medicines, I find none to which it appears to me to approach more closely than serpentaria; though it must be acknowledged that there is considerable difference between them. I have accordingly concluded to give it this subordinate position to serpentaria provisionally, until a better place can be found for it in the classification.
The name of arnica is given, in the U. S. Pharmacopoeia, to the flowers, in the British, to the root of Arnica montana or Leopard"s-bane, a perennial herbaceous plant, growing in the mountainous regions of Europe and Siberia, and, according to Nuttall, in the North-western parts of this continent. The entire plant has, when fresh, a strong disagreeable odour, which diminishes in drying, and an acrid, bitter, lasting taste. The flowers are most used in this country. Among other ingredients they were found by MM. Chevallier and Lassaigne to contain a peculiar principle, analogous if not identical with cytisin, previously discovered in the laburnum-tree. This is a powerful agent, acting energetically in the dose of five grains as an emeto-cathartic, and probably capable in excessive doses of producing poisonous effects. It is no doubt one of the active ingredients of the flowers; but certainly not the only one; as, besides a small proportion of volatile oil and acrid resin, a peculiar alkaloid has been obtained from them, which is not without influence upon the system. Our information, however, as to the relation between these two substances, the cytisin and arnicina (or preferably arnicia) as the alkaloid has been named, and as to the effects of both on the system, is yet too indefinite to admit of positive conclusions. It seems certain, however, that they are not identical; for, according to its discoverers, cytisin is readily dissolved by water, with difficulty by strong alcohol, and not at all by ether; while arnicia is but slightly soluble in water, and freely soluble in alcohol and ether. The root probably has essentially the same virtues as the flowers.
As a medicine, arnica has long been used on the continent of Europe, particularly in Germany, where it is highly esteemed. In the United States, it was almost unknown as a remedy until of late; but within a few years it has risen greatly in reputation, probably in part through the many German practitioners who are pursuing their profession in this country. So decided is the change in this respect that, in the present edition of the U. S. Pharmacopoeia, it takes a place in the primary catalogue, having been transferred from the secondary, where it previously held a somewhat doubtful place. Arnica appears to be a general stimulant and tonic, analogous in this respect to serpentaria, but directed especially to the nervous system, and acting as a diaphoretic, diuretic, and emmenagogue. It is apt to nauseate, and in large doses operates as an emetic and cathartic. Very freely taken, it causes burning in the stomach, violent abdominal pain, excessive headache, muscular spasms, and other evidence of nervous disturbance. It is no doubt capable of acting as a poison. A case is recorded in the London Lancet (Nov. 18, 1864, p. 571), in which the patient was apparently saved only by the use of remedies from threatened death, consequent on the swallowing by mistake of an ounce of tincture of arnica. When first seen by the physician, he was in a state of approaching collapse, with sunken and glassy eyes, dilated pupils unaffected by light, voice low and muttering, pulse over a hundred, feeble and fluttering, great pain in the epigastrium, and a cold, dry skin. Intelligence, however, was not lost; and, from his account of himself, it appeared that little effect had been experienced for the first eight hours after the swallowing of the poison, except dryness of the mouth, that at the end of that time he was awakened from sleep by violent pain in the stomach, and that on rising he felt sick and feeble. The treatment consisted in the exhibition of an ounce of brandy and twenty minims of laudanum, which were repeated in two hours, and the external application of heat. He gradually recovered. An emetic would have been the appropriate remedy at an earlier stage, but was out of the question under the circumstances of the present case.
Arnica appears to be adapted to febrile diseases with a low or typhoid tendency, also to various phlegmasiae offering a similar condition. It has been used in rheumatism and gout, diarrhoea and dysentery, chronic catarrh and nephritis, passive hemorrhage, dropsy, and amenorrhoea, and certain paralytic affections, especially amaurosis. Having been found useful in the nervous disturbance following accidents of various kinds, it got a reputation as a special cure for wounds, sprains, bruises, and the swellings consequent on dislocation, and is much employed in domestic practice as a local application in these affections, for which the tincture is deemed especially useful. The powder is sometimes used to excite sneezing.
Arnica may be given in powder or infusion; the dose of the former being from five to twenty grains; of the latter, made in the proportion of an ounce to the pint, half a fluidounce to a fluidounce every two hours.
A Tincture of the Flowers (Tinctura Arnica, U. S.) and a Tincture of the Root (Tinctura Arnicae, Br.) are officinal, the former in the U. S., the latter in the Br. Pharmacopoeia. It is this preparation either undiluted, or mixed with water or soap liniment, that is so much used in the local affections above referred to. From some observations made by Dr. Garrod, of London, there is reason to believe that the effects of the tincture in these cases is little more than that of the alcoholic menstruum. The dose for internal use is from thirty minims to two fluidrachms.
An Extract (Extractum Arnicae Alcoholicum, U. S.) is prepared from the flowers by percolation with alcohol and subsequent evaporation. The dose is from five to ten grains. But is more used in the preparation of the plaster than for any other purpose.
The Plaster of Arnica (Emplastrum Arnicae, U. S.) is made by incorporating the extract with the melted resin plaster. This is another preparation very popular, outside of the profession, as a remedy for sprains, bruises, etc.