Arnica

ARNICA FLOWERS, ARNICA ROOT, COMMON ARNICA, LEOPARD'S BANE, MEXICAN ARNICA, MOUNTAIN ARNICA, MOUNTAIN DAISY, MOUNTAIN TOBACCO, SNEEZEWORT, WOLF'S BANE

Taxonomic Class

Asteraceae

Common Trade Names

Arnicaid, Arnica Spray, Arniflora (Gel), Traumeel-S (homeopathic formulation of arnica and other plant extracts manufactured in Italy)

Common Forms

Available as a spray for topical application and in creams (preferred in Europe), gels, ointments, sublingual preparations, tablets, teas, and tinctures. Creams typically contain 15% arnica oil; salves should contain 20% to 25% arnica oil.

Source

Active components are usually extracted from the flowers and root­stocks of Arnica montana, A. fulgens, A. sororia, and A. cordofolia. Mexican arnica is derived from Heterotheca inuloides. Certain species of Arnica are native from Alaska to the Western United States and Mexico. Others are native to Europe and Siberia.

Chemical Components

Arnica's active ingredients are thought to be flavonoid glycosides and sesquiterpenoid lactones, including anthoxanthine, arnisterol (arnidiol), choline, dihydrohelenalin, faradiol, and helenalin. Arnica also contains a group of polysaccharides with a content of 65% to 100% galacturonic acid and 0.5% to 1 % resins, tannins, and volatile oils.

Actions

Four sesquiterpenoids isolated from H. inuloides in one study demonstrated antibacterial activity in vitro. One compound exhibited gram­positive antibacterial activity and minimal bactericidal concentrations of 12.5 mcg/ml against methicillin-resistant Staphylococcus aureus . Another in vitro study supported arnica's inhibitory effect against a few gram-positive organisms, but the effect was considered minor.

An A. montana extract has been shown to increase phagocytosis in mice .

In a Dutch study, most arnica flavonoids demonstrated moderate to low cytotoxicity in vitro when compared with cisplatin. Helenalin, a sesquiterpene lactone, displayed the strongest cytotoxicity . Another study apparently found a quicker recovery from carbon tetrachloride-induced hepatic injury in rats when the rats were given a preparation of phenolic compounds of A. montana. Other studies in rats have also supported a role of arnica extracts in reducing lipid peroxidation and restoration of glutathione activity in the carbon tetrachloride-induced hepatic injury.

An in vitro study found that helenalin and dihydrohelenalin inhibit­ed platelet function in humans. Another study in healthy human volunteers failed to find significant effects on blood-clotting parameters immediately after use of an arnica extract .

In vitro studies have documented an anti-inflammatory effect for some components of arnica . Traumeel-S, a homeopathic mixture containing arnica, was found to reduce rat paw edema. This was associated with a decrease in interleukin-6 production in the animals .

Reported uses

Arnica is claimed to be useful for relieving muscle and joint aches and is frequently cited in herbal literature as being able to promote wound healing. In veterinary medicine, the agent is classified as a counterirritant, an effect probably related to the isomeric alcohol component of arnica.

Analgesic effects failed to be verified in a double-blind study of arnica, metronidazole, and a placebo among postoperative dental patients.

Similarly, a homeopathic dose of arnica was tested against a placebo in a population of post abdominal hysterectomy patients. No significant difference was found between the two groups . In a small study of marathon runners, another formulation of arnica failed to produce statistically significant benefits in muscle stiffness, laboratory measurements of muscle injury, or healing time of muscle injuries. Notably, a systematic review of placebo-controlled trials published before 1998 failed to find any support of efficacy for arnica as a homeopathic medicinal .

Dosage

No consensus exists. Homeopathic doses (trace quantities) appear to be most popular.

Adverse Reactions

CV: arrhythmias, cardiotoxicity, hypertension.

EENT: mouth ulcers (with undiluted commercial mouthwash preparation of oil of peppermint and arnica).

GI: gastroenteritis, nausea, vomiting.

Hematologic: increased risk of bleeding (conflicting data).

Hepatic: hepatic failure.

Musculoskeletal: muscle weakness.

Skin: arnica-induced Sweet's syndrome (acute febrilic neutrophilic dermatosis clinically resembling erythema multiforme), contact dermatitis (with topical use).

Other: death, organ damage.

Interactions

Antihypertensives: May reduce effectiveness of these drugs. Avoid use with arnica.

Contraindications And Precautions

Avoid using arnica in pregnant patients because of the risk of uterine oxytocic activity and lack of knowledge about arnica's teratogenic potential.

Special Considerations

Instruct the patient not to apply arnica to abraded skin or open wounds.

Alert Keep arnica preparations out of the reach of children. Coma, nausea, organ damage, vomiting, and even death have occurred in children from ingestion of arnica flowers or roots. Induce emesis and perform gastric lavage to remove undigested contents. Supportive care may be needed.

Explain to the patient that when taken orally, arnica may cause allergic reactions, cardiotoxicity, hypertension, renal dysfunction, and vertigo because of the activity of sesquiterpene lactones and components of the essential oil.

Advise the patient to avoid prolonged topical use because of the potential for allergic reactions.

Points of Interest

Arnica has been approved by the German Commission E as a topical agent with effective analgesic, antibacterial, and anti-inflammatory properties. The FDA, however, has classified arnica as an unsafe herb.

Commentary

Despite interesting in vitro studies and exciting possibilities for use of this agent, clinical trials have failed to document therapeutic benefits of arnica. A systematic analysis also failed to find significant proof of efficacy for homeopathic application of arnica. External use is discouraged because of the risk of allergic reactions. The results of well-conducted clinical trials that verify a favorable risk-benefit ratio are needed before therapeutic applications of arnica can be considered.