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Scientific Name(s): Acorus calamus L.
Common Name(s): Calamus, Calamus oil, Rat root, Shi chang pu, Sweet flag, Sweet myrtle, Sweet root, Sweet sedge, Vash vaj

Medically reviewed by Last updated on Sep 21, 2021.

Clinical Overview


Clinical studies are lacking due to concerns of toxicity. Antioxidant, anti-inflammatory, and cardiovascular effects have been described, as well as activities in epilepsy, diabetes, and cancer. However, because of toxicity and lack of clinical trials, no recommendations for use can be made. Use of calamus and its extracts is prohibited in the US.


Use of calamus and its extracts is prohibited in the US. Clinical studies that provide information on therapeutic dosages are lacking.


Contraindications have not yet been identified.


Avoid use. Adverse effects (emmenagogue and genotoxic activity) have been documented.


None well documented.

Adverse Reactions

Clinical studies are lacking due to concerns of toxicity.


Case reports of toxicity describe nausea and prolonged vomiting (up to 15 hours) and tachycardia. Mutagenicity attributed to various extracts and chemical constituents has been reported.

Scientific Family

  • Araceae (Calamus)


Calamus is a semi-evergreen, perennial, hairless herb found in damp, swampy areas. It has bright-green sword-shaped leaves with a waxy margin that thicken in the middle. The plant is similar in appearance to the iris and grows to approximately 2 meters tall, with hermaphroditic flowers that are pollinated by insects. The creeping rhizome is pale yellow to pinkish brown on the outside and white to pinkish on the inside. It is native to much of Asia and is also found throughout North America and eastern Europe.1, 2, 3 Synonyms include A. calamus L. var. americanus (Raf.) H.D. Wulff. and Acorus americanus (Raf.) Raf.


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." However, because of an association between asarones and the development of tumors in animals, the use of calamus and its extracts is prohibited in the US. Maximum limits for beta-asarone content in food and beverages have been set by the European Commission.2, 3, 4, 5 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. It is central to the Ayurvedic medical system as an aromatic, stimulant, bitter tonic, and expectorant and has been used as an emmenagogue. The A. calamus used in Ayurvedic medicine has undergone "sodhana," a process of detoxification. It has been used by Native Americans to soothe toothache and headache. Calamus has been promoted on the Internet as a hallucinogen.

The ground rhizome is used as a spice and commercial flavoring in drinks, cosmetics, and toothpastes.


Calamus leaves and rhizomes contain 1.5% to 3.5% of a volatile oil responsible for the plant's characteristic odor and taste. From some types of calamus, a major component of the oil (up to 75%) is beta-asarone. Alpha-asarone has also been identified and exists in both the cis- and trans-isomer forms.6 More than a dozen additional compounds have been identified in the oil and extracts, including saponins, lectins, sesquiterpenoids, lignans, and steroids. Hydrocarbons, carbonyl compounds, alcohols, phenols, furans, and other compounds have also been described. Ethanolic extracts and acetone, hydroalcoholic, and methanolic extracts have been studied and high-pressure liquid chromatography methods for determining asarone content have been published.3, 5, 7, 8, 9

The chemical composition of the plant varies according to geographic location, plant age, climate, species variety, and plant part used.3, 10 The diploid plant grows in North America and is beta-asarone free. The European triploid plant is different chemotype of calamus, with oil containing less than 10% asarone. Indian tetraploid varieties, however, have been found to contain oils that are composed of 96% asarone or less.6

Uses and Pharmacology

Clinical studies are lacking due to concerns of toxicity. (See Toxicology.)

Allergic reactions

Animal data

Down-regulation of immunoglobulin G and immunoglobulin E has been demonstrated in vitro.11 Prevention of mast cell degranulation has been shown in mice,12 and an antihistamine effect was shown in isolated guinea pig tissue.13

Clinical data

Research reveals no clinical data regarding the use of calamus in allergic reactions.

Anti-inflammatory effects

Animal data

In animal and in vitro studies, the immunomodulation and anti-inflammatory action of A. calamus extracts was attributed to observed neuroprotective, analgesic, and wound-healing properties. Interference with cytokines (interleukins and tumor necrosis factor-alpha) and immunoglobulins has been demonstrated.14, 15, 16, 17, 18, 19

Clinical data

There are no clinical data regarding the use of calamus for anti-inflammatory effect.

Antimicrobial effects

Animal data

Leaf and rhizome extracts as well as calamus oil have shown antibacterial activity against some human pathogens, including weak activity against Neisseria gonorrhoeae. Older studies report antiviral activity. Antifungal activity against both human and plant pathogens has been demonstrated in vitro.3, 7, 20, 21, 22 Activity against the larvae of insects has been demonstrated in vitro and in animals such as cattle.3, 23, 24, 25

Clinical data

There are no clinical data regarding the antimicrobial activity of calamus.


Animal data

Antioxidant activity of A. calamus has been described and may be responsible for observed effects in cancer cell lines. Protection against irradiation-induced DNA strand breaks and chemotherapy-induced hepatotoxicity and nephrotoxicity has been attributed to antioxidant activity.26, 27, 28, 29, 30, 31 Induced senescence in colorectal cancer cells and upregulation of capases have also been described as mechanisms by which the extracts may decrease proliferation and induce apoptosis in cancer cells.32, 33 Activity has been attributed to beta-asarone, sesquiterpenoids, and the lectin content of the plant.3, 9, 34

Clinical data

There are no clinical data regarding the use of calamus in cancer. Both alpha- and beta-asarone have been shown to be mutagenic themselves.3

Cardiovascular effects

Animal data

Extracts of A. calamus show antagonism of the calcium channel and effects on the nitric oxide pathway. Depending on the extraction method and fractions used, vasodilation and constriction and partial depressant effects on coronary flow and heart rate have been demonstrated in rats and in isolated heart studies.35, 36

Clinical data

There are no clinical data regarding the use of calamus in cardiovascular disease.

CNS effects

Animal data

Anticholinesterase activity has been demonstrated in vitro and in animal studies, which may have implications for the management of Alzheimer disease.13, 37 Beta-asarone and extracts of A. calamus exerted antidepressant effects and improved cognitive function in rats with induced stress-related depression.38, 39, 40, 41 Older studies and traditional uses suggest a sedatory effect.3

Clinical data

There are no clinical data regarding the use of calamus in CNS disorders or to support the occurrence of a hallucinogenic effect.


Animal data

A limited amount of research has described the hypoglycemic effects of different fractions of A. calamus extracts. Decreases in blood glucose, inhibition of alpha-glucosidase activity, and enhanced adipocyte differentiation have all been demonstrated in vitro and in animal studies. Beta-asarone, however, has also been shown to exert an inhibitory effect on adipogenesis.3, 42, 43, 44

Clinical data

There are no clinical data regarding the use of calamus in diabetes.


Animal data

Limited studies in rats have shown that extracts of A. calamus, especially alpha-asarone and purified rhizome extracts, exert an anticonvulsant effect on induced seizures. Possible sites of action are the gamma-aminobutyric acid receptors and sodium channel.31, 45, 46, 47, 48

Clinical data

There are no clinical data regarding the use of calamus in epilepsy.

Other uses

In studies with isolated guinea pig trachea and atria, a crude extract of A. calamus demonstrated a dual inhibition of calcium channels and phosphodiesterase, suggesting a pharmacological basis for its use in disorders of airways in traditional medicine.49 Results of a study in isolated rabbit jejunum suggested that the spasmolytic effect of an extract of A. calamus is mediated through the presence of calcium channel blockade–like constituent(s) concentrated in the n-hexane fraction, providing a strong mechanistic base for its traditional use in GI disorders.50


Use of calamus and its extracts is prohibited in the US. Clinical studies that provide information on therapeutic dosages are lacking. Storage of the root leads to a loss in potency.

Pregnancy / Lactation

Avoid use. Adverse effects (emmenagogue and genotoxic activity) have been documented.3, 51


Case reports are lacking. Potentiation of calcium channel blockers (eg, amlodipine) and medicines used in epilepsy is possible based on studies in rodents.44, 52 Alpha-asarone and A. calamus extracts may also interfere with the cytochrome P450 enzyme system.53

Adverse Reactions

Clinical studies are lacking. (See Toxicology). Cardiovascular effects, such as hypotension, are possible based on animal studies.


The Swedish Poisons Information Centre reported 30 cases of acute intoxication related to A. calamus abuse from 2003 through 2006 that involved nausea and prolonged vomiting (up to 15 hours) as well as tachycardia.4 Acute toxicity tests in mice showed piloerection, decreased mobility, increasing respiratory distress, unconsciousness, and death. Long-term toxicity studies report the development of tumors and thrombosis in rat heart chambers. The median lethal dose in mice was reported to be 417 mg/kg (oral) to 900 mg/kg.14

The primary toxicological concern focuses on the carcinogenic effects of asarone. Both alpha- and beta-asarone showed mutagenicity in most studies.3

Feeding studies conducted from the late 1960’s provided evidence of the mutagenic potential of this compound.2, 3, 6

Index Terms

  • Acorus americanus (Raf.) Raf
  • Araceae calamus L. var. americanus (Raf.) H.D. Wulff


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20. Cybulska P, Thakur SD, Foster BC, et al. Extracts of Canadian first nations medicinal plants, used as natural products, inhibit Neisseria gonorrhoeae isolates with different antibiotic resistance profiles. Sex Transm Dis. 2011;38(7):667-671.21301385
21. Ghosh M. Antifungal properties of haem peroxidase from Acorus calamus. Ann Bot. 2006;98(6):1145-1153.17056613
22. Rajput SB, Karuppayil SM. β-asarone, an active principle of Acorus calamus rhizome, inhibits morphogenesis, biofilm formation and ergosterol biosynthesis in Candida albicans. Phytomedicine. 2013;20(2):139-142.23123225
23. Liu XC, Zhou LG, Liu ZL, Du SS. Identification of insecticidal constituents of the essential oil of Acorus calamus rhizomes against Liposcelis bostrychophila Badonnel. Molecules. 2013;18(5):5684-5696.23676474
24. Ghosh S, Sharma AK, Kumar S, et al. In vitro and in vivo efficacy of Acorus calamus extract against Rhipicephalus (Boophilus) microplus. Parasitol Res. 2011;108(2):361-370.20886235
25. Sharma PR, Sharma OP, Saxena BP. Effect of sweet flag rhizome oil (Acorus calamus) on hemogram and ultrastructure of hemocytes of the tobacco armyworm, Spodoptera litura (Lepidoptera: Noctuidae). Micron. 2008;39(5):544-551.17826115
26. Sandeep D, Nair CK. Protection of DNA and membrane from γ-radiation induced damage by the extract of Acorus calamus Linn.: an in vitro study. Environ Toxicol Pharmacol. 2010;29(3):302-307.21787617
27. Sandeep D, Nair CK. Protection from lethal and sub-lethal whole body exposures of mice to gamma-radiation by A. calamus L.: Studies on tissue antioxidant status and cellular DNA damage. Exp Toxicol Pathol. 2012;64(1-2):57-64.20605086
28. Sandeep D, Krishnan Nair CK. Amelioration of cisplatin-induced nephrotoxicity by extracts of Hemidesmus indicus and Acorus calamus. Pharm Biol. 2010;48(3):290-295.20645815
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