The dried flower-heads of Arnica montana, Linné (Nat. Ord. Compositae). A perennial of Siberia and the cooler parts of Europe; also found in Northwestern United States (?—MM). Dose, 1 to 10 grains.
Common Names: Arnica, Leopard's Bane.
Principal Constituents.—Arnicine (C12H22O2), a golden-yellow body, a volatile oil, and angelic and formic acids.
Preparations.—1. Specific Medicine Arnica. Dose, 1/4 to 10 drops.
2. Tinctura Arnicae, Tincture of Arnica. Locally.
Specific Indications.—"Muscular soreness and pain from strain or overexertion; advanced stage of disease, with marked enfeeblement, weak circulation, and impaired spinal innervation; embarrassed respiration; lack of control over urine and feces; sleeplessness from impeded respiration; and dull praecordial pain from 'heart strain'; muscular pain and soreness when the limbs are moved; tensive backache, as if bruised or strained; cystitis, with bruised feeling in bladder, as from a fall or blow; headache, with tensive, bruised feeling and pain on movement; hematuria, with dull, aching, lumbar pain; or from overexertion. Debility with enfeebled circulation." (American Dispensatory.)
Action.—Arnica is a decided irritant to the skin, under some circumstances producing marked dermal irritation, deepening into an erysipelatous or acute eczematous inflammation, with pustules and blisters, and often grave constitutional symptoms. In this respect the alcoholic preparations of the flowers are most active, and for this reason full strength preparations should not be used upon the skin, nor as a rule should any preparation of arnica be used upon cuts or injuries causing a breaking of the skin. Under the latter conditions dangerous inflammation, with vesication, has occurred. Persons of sensitive skin, and it is said gouty subjects, are most susceptible to this untoward action of the drug.
Medicinal doses of arnica slow the heart, slightly raise arterial pressure, and stimulate the vagi. Poisonous doses operate reversely and paralyze the vagal centers. Intermediate but large doses produce heat in the throat, nausea and vomiting, dyspnea, headache, lowering of temperature, and sometimes convulsive movements. With toxic doses these effects deepen into unconsciousness, motor, sensory and vagal paralysis, coma, and death. Death is said to have been caused by two ounces of tincture of arnica.
Therapy.—External. Arnica, in tincture or fomentation, has long been a popular but by no means safe discutient to prevent and discuss inflammatory swellings, and to relieve the soreness of myalgia and the effects of sprains, bruises, and contusions. It is often serviceable to remove ecchymoses, and it gives grateful relief to sore muscles that have undergone much strain and exertion. A glycerite has been effectually used upon bites of mosquitoes and other insects. Preparations of the root are less liable to excite dermatitis, and the infusion of the flowers is less irritant than the tincture. After applying the latter, which should always be well diluted, the surface should not be covered or bandaged, so that evaporation may take place freely.
Internal. Arnica is a greatly unappreciated medicine. It has a pronounced action upon the medulla and spinal cord which can be invoked to good advantage in states of depression. The keynote for arnica is spinal and vagal enervation. It should be brought into service when there is deficient nervous response, sluggish vascular power, and in almost all conditions in which prevails the triad-torpor, debility, and depressed function. In the advanced stages of exhausting diseases, where spinal innervation is poor, control over the sphincters lost, and there is feeble respiration due to central vagal impairment, it is a most important stimulant. It should be used when breathing can be carried on chiefly only by force of the will, and becomes weak and shallow when the patient drops into sleep; or when the sleeper awakens with a start on account of dyspnoea when automatic respiratory action alone is depended upon. Such a state occurs in the low stage of typhoid and other fevers, and in lobar pneumonia. In such conditions arnica is most useful and compares well with strychnine or atropine, or phosphorus, none of which are so safe as arnica. Arnica will prove useful in the depression occasioned by extreme forms of diarrhoea and dysentery when the discharges escape control. In so-called typhoid pneumonia—which is but pneumonia with typhoid conditions—marked asthenia, feeble circulation, great depression, low muttering delirium, picking at the bed clothes, and dry tongue loaded with foul mucus and sordes, it is a most valuable auxiliary to other treatment. In the hectic fever of phthisis, with exhausting diarrhoea and excessive sweating, it often proves the needed stimulant and antihydrotic.
Arnica is a stimulant of great power in anemia, with weak heart and capillary feebleness, and marked depression, diarrhoea and dropsy, but no inflammation. During mild forms of so-called chronic rheumatism, with cold skin and general debility it will stimulate the nervous system, restore normal warmth, re-establish restrained secretion, and thus relieve pain. In painful, bruised or subacute inflammatory disorders arising from injury, with marked lowering of nerve tone, muscular aching and chilly sensations, arnica is a remedy of power to give comfort and hasten resolution. When myalgia is caused by exposure, or when muscular soreness and pain are due to strain, overexertion, or sudden jars or blows, the administration of arnica internally, in small doses of the specific medicine preferably, and the diluted tincture applied locally are among the most serviceable of measures.
Arnica frequently relieves "heart-strain" due to exertion, overwork, or from long marching. It also benefits in the heart debility that follows severe strain, worry, or excitement. Dull aching pain in the praecordia, due to lifting or when working against vibrating machinery, as in shoe making, is dissipated by small doses of arnica. For lame back, backache and feelings of soreness and debility of the back, when accompanied by nervous depression and poor circulation, arnica is one of the most direct of remedies. Lumbago, when due to muscular strain or falls, is relieved by arnica. Its action is increased by rhus, macrotys, or sometimes gelsemium. When dependent upon a loaded bowel, venous relaxation in the hemorrhoidal circulation, piles, fissures, sagging of the abdominal contents, pelvic weakness, or a neuritic state of the lumbar plexus, arnica is of little or no value. Indeed, in some of these conditions it may only result in an aggravation of the nervous unrest so frequently attendant upon lumbago, and allied painful disorders.
We have used arnica most successfully in paraplegia and hemiplegia after all evidence of acute inflammation or recent injury has passed. It is especially to be remembered in sphincteral paralyses, so common after long illness in which spinal enervation has played an important role. Nervous headache of depression and debility frequently is relieved by arnica, and some believe it to be the best agent for amaurosis, a rather ill-defined ocular disturbance.
Should the patient to whom arnica is administered appear to become nervously excited and restless, or show gastric irritability, its use should be discontinued.
The Eclectic Materia Medica, Pharmacology and Therapeutics, 1922, was written by Harvey Wickes Felter, M.D.