Calamus

Medically reviewed on June 4, 2018

Scientific Name(s): Acorus calamus L. Family: Araceae

Common Name(s): Calamus , rat root , sweet flag , sweet myrtle , sweet root , sweet sedge

Uses

Traditionally used as a tranquilizer and general “wonder drug,” calamus also is used as a flavoring. The oil is a sedative, hypotensive, and muscle relaxant.

Dosing

There is no recent clinical evidence to guide dosage of calamus. The root should not be stored for more than 18 months because of rapid loss of potency. A typical dose in classical usage would be 3 g of rhizome.

Contraindications

Contraindications have not yet been identified.

Pregnancy/Lactation

Documented adverse effects (emmenagogue and genotoxic activity). Avoid use. 1

Interactions

None well documented.

Adverse Reactions

Little or no adverse reactions data is available, as all calamus products have been removed from the US market because of toxicity.

Toxicology

Because of mutagenic properties, calamus derivatives are not used in foods in the US.

Botany

Calamus is a perennial that is found in damp, swampy areas. It has sword-shaped leaves and grows to 6 feet tall. It is similar in appearance to the iris. It is found throughout North America, Europe, and Asia, 2 and is often imported from India and the former Yugoslavia and USSR. 3

History

The fragrant underground portion (the rhizome) has been used medicinally since biblical times. Popular European books on medicinal plants touted calamus as a “wonder drug.” It was commonly used in folk medicine as a nervine, most likely linked to the tranquilizing effect of cis-isoasarone (the major component of the oil). 3 It has been used in traditional medicine for the treatment of digestive disorders and childhood colic. Infusions of the rhizome have been suggested for the treatment of fever, and chewing the rhizome has been said to relieve irritated throats and to remove the odor of tobacco.

The ground rhizome is used as a spice and commercial flavoring in drinks, cosmetics, and toothpastes. However, because of an association with isoasarone and the development of tumors in animals, the use of calamus and its extracts is prohibited in the US. 2

Chemistry

Calamus contains from 1.5% to 3.5% of a volatile oil responsible for the plant's characteristic odor and taste. 2 A major component of the oil (up to 75%) from some types of calamus is beta-asarone (also referred to as cis-isoasarone). 3 More than a dozen additional fragrant compounds have been identified in the oil.

Acorus calamus has recently been classified into four separate varieties which grow in different locations worldwide. The virtually isoasarone-free plant grows in North America (drug type Ι). Western Europe is home for yet another type of calamus, the oil of which contains less than 10% isoasarone (drug type ΙΙ). The two other varieties, however, have been found to contain oils which are composed of up to 96% isoasarone (drug types ΙΙΙ and ΙV). 2

Calamerone, a bicyclic sesquiterpene, has been discovered in the roots of A. calamus . Calamendiol and isocalamendiol, two known sesquiterpenes, were isolated from the same plant. 4 The essential oil consists of sesquiterpenes and phenylpropanes. The composition of the oil varies depending upon the degree of the ploidy of the plants. Other constituents are acorone, a sesquiterpene diketone, tannins, mucilage, and small starch grains. 3

Uses and Pharmacology

Sedative
Animal data

A variety of studies have been conducted to evaluate the pharmacologic effects of calamus and its extracts. The crude drug has been found to possess sedative properties and to potentiate barbiturate and ethanol-induced sedation in mice; calamus potentiates the CNS effects of reserpine. 5 Doses of 10 to 100 mg/kg intraperitoneally of calamus oil to rats, mice, dogs, cats, and monkeys resulted in a dose-dependent reduction in spontaneous movement; at the 100 mg/kg dose, spontaneous motor activity was reduced by 95% compared with a control. No deaths occurred at any dose. The depressant effect did not induce hypnosis, but was characteristic of sedation induced by reserpine or chlorpromazine. 5 This sedative activity has been ascribed to asarone. The sedative effects of intraperitoneal doses of asarone in mice lasted 4 to 6 hours. 6

Although calamus oil inhibits monoamine oxidase in vitro, this effect occurs primarily at doses higher than are required for usual pharmacologic activity. It has been suggested that the effects of the drug are mediated through 5-hydroxytryptamine 5 or norepinephrine; however, this mechanism has been disputed. Some experts suggest that asarone may mediate its effect through depression of hypothalamic function. 6

Clinical data

Research reveals no clinical data regarding the use of calamus as a sedative.

Hypotensive
Animal data

The oil induced hypotension when administered parenterally to dogs. 2

Clinical data

Research reveals no clinical data regarding the use of calamus as a hypotensive.

Spasmolytic
Animal data

When tested in vitro, it was found that isoasarone-free oil (type Ι) had a pronounced spasmolytic action comparable to that of a standard antihistamine. However, at a similar dose, isoasarone-rich oil (type ΙV) showed no spasmolytic action at all. 7 Researchers also noted that the oil decreased the mortality of guinea pigs caused by histamine. 8 Such results suggest that the isoasarone-free oil from type Ι (North American) calamus plants can be an effective herbal remedy for dyspepsia and similar spasmodic gastrointestinal complaints. 2 In low doses, calamus oil has an acetylcholine-like action on smooth muscle; at high doses, it has an antispasmodic and relaxant effect. 5 It boasts stomachic, carminative, and (externally) rubefacient indications. 3 When tested in vitro , calamus oil abolished drug-induced contractions of isolated animal intestine, aorta, and uterus; its action was about 10 times less potent than that of papaverine. 8

Clinical data

Research reveals no clinical data regarding the use of calamus as a spasmolytic.

Other uses

The essential oil of calamus has also been used as an insecticide. Several studies have found that the vapors of the oil are sufficient to control the hatching and molting of several types of common pests in doses of approximately 10 mL of a 100 ppm dilution. 9

Dosage

There is no recent clinical evidence to guide dosage of calamus. The root should not be stored for more than 18 months because of rapid loss of potency. A typical dose in classical usage would be 3 g of rhizome.

Pregnancy/Lactation

Documented adverse effects (emmenagogue and genotoxic activity). Avoid use. 1

Interactions

None well documented.

Adverse Reactions

Little or no adverse reactions data is available for calamus. Because of mutagenic activity, calamus products cannot be sold in the US.

Toxicology

The primary toxicologic concern focuses on the carcinogenic effect of isoasarone, a major component of the volatile oil of calamus. Feeding studies conducted more than 20 years ago provided evidence for the mutagenic potential of this compound. Subsequently, all calamus-containing products were removed from the US marketplace. 2 However, a recent study found extracts of A. calamus to exhibit no mutagenic activity in the salmonella mutagenicity screen. 10 The plant and its extracts continue to find use throughout the world.

The LD ₅₀ of asarone in mice is 417 mg/kg (oral) and 310 mg/kg (IP). 11 Although A. calamus exhibited no mutagenic activity in the salmonella mutagenicity screen, recent experiences showed that calamus oil exhibited genotoxic effects on Swiss mice. 12 Another experiment showed that calamus oil was strongly mutagenic. 13

Bibliography

1. Ernst E. Herbal medicinal products during pregnancy: are they safe? BJOG . 2002;109:227-235.
2. Tyler V. The New Honest Herbal . Philadelphia: G.F. Stickley, 1987.
3. Bisset N. Herbal Drugs and Phytopharmaceuticals . Stuttgart: MedPharm Scientific Publishers, 1994.
4. Wu L, Sun LL, Li M, et al. Yakugaku Zasshi . 1994;114:182-185.
5. Dhalla N, Bhattacharya IC. Further studies on neuropharmacological actions of acorus oil. Arch Int Pharmacodyn Ther . 1968;172:356-365.
6. Menon M, Dandiya PC. The mechanism of the tranquilizing action of asarone from Acorus clamus Linn. J Pharm Pharmacol . 1967;19:170-175.
7. Keller K, Odenthal KP, Leng-Peschlow E. Planta Med . 1985;1:6.
8. Maj T, et al. Acta Poloniae Pharma . 1966;23(5):477.
9. Saxena B, et al. Experientia . 1974;30(11):1298.
10. Riazuddin S, et al. Environ Mol Mutagen . 1987;10(2):141.
11. Belova L, et al. Farmakol Toksikol . 1985;48(6):17.
12. Balachandran B, et al. Ind J Med Res . 1991;94:378.
13. Sivaswamy S, et al. Indian J Exp Biol . 1991;29(8):730.

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