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HORSETAIL

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Classification   |    Detailed evidence-based information

Substances Included Synonyms

Therapeutic Toxic Class

    A) There are approximately 25 species of the genus Equisetum, of which four are the main species: Equisteum arvense (horsetail), Equisetum hiemale L, Equisetum maximum L and Equisteum sylvaticum L. Horsetail (family, Eqiosetazeae) is a dimorphic perennial plant.

Specific Substances

    A) EQUISETUM ARVENSE
    1) Bottle brush
    2) Common horsetail
    3) Corn horsetail
    4) Dutch rushes
    5) Equisetum
    6) Field horsetail
    7) Horse tail
    8) Horse willow
    9) Horsetail grass
    10) Horsetail rush
    11) Paddock-pipes
    12) Pewterwort
    13) Prele
    14) Scouring rush
    15) Shave grass
    16) Shavegrass
    17) Shavetail grass
    18) Souring rush
    19) Toadpipe
    EQUISETUM BOGOTENSE
    1) Chile equisetum
    2) Horsetail
    EQUISETUM FLUVIATILE
    1) Cola de caballo
    2) Mexican equisetum
    3) Mexican horsetail
    EQUISETUM GIGANTEUM
    1) Chile equisetum
    2) Horsetail
    3) Mexican equisetum
    EQUISETUM HIEMALE
    1) Cola de caballo
    2) Mexican equisetum
    3) Mexican horsetail
    EQUISETUM MYRIOCHAETUM
    1) Cola de caballo
    2) Mexican equisetum
    3) Mexican horsetail
    EQUISETUM TELMATEIA
    1) Giant horsetail

Available Forms Sources

    A) FORMS
    1) Horsetail is available in the following forms: Capsule, dried herb, powdered herb, powdered extract, infusion, tablet, tea, tincture(Blumenthal et al, 2000; Blumenthal et al, 1998).
    2) REGULATORY/SAFETY INFORMATION: The American Herbal Products Association rated horsetail (Equisetum arvense and Equisetum telmateia) as class 2d (contraindicated in patients with cardiac or renal dysfunction) (McGuffin et al, 1997).
    3) Horsetail is available as a dietary supplement in the United States under the Dietary Supplement Health and Education Act of 1994 (DSHEA). Products sold in Canada are required to be certified to contain no thiaminase-like effects (McGuffin et al, 1997). The chemical identity for the substance causing thiaminase-like effects is not known(Hamon & Awang, 1992).
    B) SOURCES
    1) Pharmaceutical grade horsetail contains dried green sterile stems of the Equisetum arvense plant prepared as whole, cut, or powdered forms. Blackish rhizome fragments must not exceed 3%; stems or branches from hybrid or other Equisetum species must not exceed 5%, and the fertile cambium must not be used. Water-soluble extractive must be at least 15% (Blumenthal et al, 2000; McGuffin et al, 1997)
    C) USES
    1) INDUSTRIAL - Because of the abrasive nature of its high silica content, horsetail has been used for scouring and polishing metals (Hamon & Awang, 1992; Anon, 1991).
    2) MEDICINAL
    a) Traditional uses of Equisetum arvense include alopecia, tuberculosis, nail disorders (brittle nails or injuries), bladder and kidney disorders (kidney stones, dysuria, cystitis, and cystic ulceration), nasal passage bleeding, respiratory and gastrointestinal tract disorders, ulcers, rheumatism, gout, frostbite, and copious menstruation. It was also used topically as an astringent and for wound healing and skin inflammation (Blumenthal et al, 2000; Jellin et al, 2000; Hamon & Awang, 1992; Anon, 1991).
    b) Horsetail (species not specified) was used to treat benign prostatic hypertrophy, prostatitis, enuresis, and urinary incontinence in Ayurvedic medicine. It has also been used to treat gonorrhea (Blumenthal et al, 2000).
    1) Horsetail (species not specified) was also used as a cancer treatment and supportive therapy for fractures and osteoporosis(Hamon & Awang, 1992). Equisetum myriochaetum was used in traditional Mexican medicine to treat kidney disease and type II diabetes (Wiedenfeld et al, 2000). Equisetum hiemale was used as a diuretic, hemostatic, astringent, and to treat eye diseases(Nitta et al, 1977)

Overview

Life Support

    A) This overview assumes that basic life support measures have been instituted.

Clinical Effects

    0.2.1) SUMMARY OF EXPOSURE
    A) USES: There are approximately 25 species of the genus Equisetum, of which four are the main species: Equisteum arvense (horsetail), Equisetum hiemale L, Equisetum maximum L and Equisteum sylvaticum L. Horsetail (family, Eqiosetazeae) is a dimorphic perennial plant. Because of the abrasive nature of its high silica content, horsetail has been used for scouring and polishing metals. Traditional medical uses of Equisetum arvense include alopecia, tuberculosis, nail disorders (brittle nails or injuries), bladder and kidney disorders (kidney stones, dysuria, cystitis, and cystic ulceration), nasal passage bleeding, respiratory and gastrointestinal tract disorders, ulcers, rheumatism, gout, frostbite, and copious menstruation. It has also been used topically as an astringent and for wound healing and skin inflammation.
    B) TOXICOLOGY: Mild diuretic, hemostyptic, vulnerary and mild leukocytosis causing actions have been reported in several sources.
    C) EPIDEMIOLOGY: Exposure is rare.
    D) WITH POISONING/EXPOSURE
    1) Severe hyponatremia, hypokalemia and muscle weakness have been reported following chronic consumption of Equisetum telmateia (great horsetail or northern giant horsetail). Seborrheic dermatitis has been reported following horsetail exposure. There have been poorly substantiated reports that nicotine-like intoxication developed in children using horsetail stems as whistles or blow guns. Please refer to "Nicotine" management for more information.
    2) ANIMALS: Ingestion of horsetail by animals has caused heart rate abnormalities, muscle weakness, ataxia, cold limbs, fever, and weight loss.

Laboratory Monitoring

    A) No specific laboratory tests are necessary unless otherwise clinically indicated.
    B) Monitor vital signs and serum electrolytes in symptomatic patients.

Treatment Overview

    0.4.2) ORAL/PARENTERAL EXPOSURE
    A) MANAGEMENT OF MILD TO MODERATE TOXICITY
    1) Treatment is symptomatic and supportive.
    B) MANAGEMENT OF SEVERE TOXICITY
    1) Treatment is symptomatic and supportive. Severe toxicity is not expected after an acute exposure.
    C) DECONTAMINATION
    1) PREHOSPITAL: Toxicity is generally only associated with chronic exposure. Prehospital gastrointestinal decontamination is not indicated.
    2) HOSPITAL: Toxicity has generally only been reported after chronic ingestion. Gastrointestinal decontamination is generally not indicated. It should be considered after very large exposures or when other potentially toxic coingestants are involved.
    D) AIRWAY MANAGEMENT
    1) Should not be required in these cases.
    E) ANTIDOTE
    1) None.
    F) ENHANCED ELIMINATION PROCEDURE
    1) There is no information regarding the effectiveness of hemodialysis or hemoperfusion for the removal of horsetail from plasma.
    G) PATIENT DISPOSITION
    1) HOME CRITERIA: A patient with an inadvertent exposure, that remains asymptomatic can be managed at home.
    2) OBSERVATION CRITERIA: Patients with a deliberate overdose, and those who are symptomatic, need to be monitored for several hours. Patients that remain asymptomatic can be discharged.
    3) ADMISSION CRITERIA: Patients who remain symptomatic despite treatment should be admitted.
    4) CONSULT CRITERIA: Consult a poison center or medical toxicologist for assistance in managing patients with severe toxicity or in whom the diagnosis is not clear.
    H) PITFALLS
    1) Toxicity is not common, other etiologies for the patients symptoms should be sought. When managing a suspected overdose, the possibility of multiagent involvement should be considered.
    I) DIFFERENTIAL DIAGNOSIS
    1) Includes other agents that can cause hyponatremia or hypokalemia such as diuretics, or water intoxication.

Range Of Toxicity

    A) TOXICITY: A minimum toxic dose has not been established. Toxicity has only been reported after chronic use.
    B) THERAPEUTIC DOSE: Dosing of herbal preparations is highly dependent on a variety of factors such as growing and harvesting conditions, plant parts and extraction methods used, and the dosage form chosen by the manufacturer. Standardization to single constituent markers has proven unreliable. Since no official standards have been established to date to regulate the production of herbal medicines in the United States, dosage ranges must be employed as guidelines. CUT HERBS: 6 grams daily. COLD MACERATE: (2 grams herb soaked in 150 milliliters (mL) cold water for 10 to 12 hours) three times daily. FLUID EXTRACT: 1:1 (grams/mL): 2 mL three times daily. TINCTURE: 1:5 (grams/mL): 10 mL three times daily. MAXIMUM DAILY DOSE: 6 grams daily.

Clinical Effects

Summary Of Exposure

    A) USES: There are approximately 25 species of the genus Equisetum, of which four are the main species: Equisteum arvense (horsetail), Equisetum hiemale L, Equisetum maximum L and Equisteum sylvaticum L. Horsetail (family, Eqiosetazeae) is a dimorphic perennial plant. Because of the abrasive nature of its high silica content, horsetail has been used for scouring and polishing metals. Traditional medical uses of Equisetum arvense include alopecia, tuberculosis, nail disorders (brittle nails or injuries), bladder and kidney disorders (kidney stones, dysuria, cystitis, and cystic ulceration), nasal passage bleeding, respiratory and gastrointestinal tract disorders, ulcers, rheumatism, gout, frostbite, and copious menstruation. It has also been used topically as an astringent and for wound healing and skin inflammation.
    B) TOXICOLOGY: Mild diuretic, hemostyptic, vulnerary and mild leukocytosis causing actions have been reported in several sources.
    C) EPIDEMIOLOGY: Exposure is rare.
    D) WITH POISONING/EXPOSURE
    1) Severe hyponatremia, hypokalemia and muscle weakness have been reported following chronic consumption of Equisetum telmateia (great horsetail or northern giant horsetail). Seborrheic dermatitis has been reported following horsetail exposure. There have been poorly substantiated reports that nicotine-like intoxication developed in children using horsetail stems as whistles or blow guns. Please refer to "Nicotine" management for more information.
    2) ANIMALS: Ingestion of horsetail by animals has caused heart rate abnormalities, muscle weakness, ataxia, cold limbs, fever, and weight loss.

Vital Signs

    3.3.3) TEMPERATURE
    A) ANIMAL STUDIES
    1) Ingestion of horsetail by animals has caused fever and cold limbs (Anon, 1991).

Cardiovascular

    3.5.3) ANIMAL EFFECTS
    A) ANIMAL STUDIES
    1) CARDIOVASCULAR EFFECTS
    a) Ingestion of horsetail by animals has caused heart rate abnormalities (Anon, 1991).

Neurologic

    3.7.3) ANIMAL EFFECTS
    A) ANIMAL STUDIES
    1) ATAXIA
    a) Ingestion of horsetail by animals has caused ataxia (Anon, 1991).

Dermatologic

    3.14.2) CLINICAL EFFECTS
    A) DERMATITIS
    1) WITH POISONING/EXPOSURE
    a) Seborrheic dermatitis has been reported following horsetail exposure (Anon, 1991; Jellin et al, 2000; Sudan, 1985). In one subject, exposure required treatment with local epinephrine and oral antihistamines. The subject developed a similar reaction following passive inhalation of tobacco smoke. The reaction may have been caused by nicotine present in horsetail. Other cases of similar reactions to both nicotine and horsetail have been reported (Sudan, 1985).
    3.14.3) ANIMAL EFFECTS
    A) ANIMAL STUDIES
    1) DERMATITIS
    a) Ingestion of horsetail (4% Equisetum arvense) with a cholesterol-supplemented diet (0.5% cholesterol) caused dermatitis and hair loss to the neck, back, and head in 20% to 65% of rats. The center of the eruption was ulcerated and mast cells were moderately increased without evidence of granuloma. The rash was diagnosed as a nonspecific inflammatory skin lesion. Symptoms began to resolve within 2 weeks after discontinuing horsetail and completely disappeared within 6 weeks. Increased serum IgE levels were not consistently associated with the dermatitis, suggesting that this is not a type I hypersensitivity reaction (Maeda et al, 1997).

Musculoskeletal

    3.15.2) CLINICAL EFFECTS
    A) MUSCLE WEAKNESS
    1) WITH POISONING/EXPOSURE
    a) CASE REPORT: An 84-year-old woman with hypertension developed severe hyponatremia, hypokalemia and muscle weakness after ingesting Equisetum telmateia for 6 months (Miro et al, 1996).
    3.15.3) ANIMAL EFFECTS
    A) ANIMAL STUDIES
    1) MUSCLE WEAKNESS
    a) Ingestion of horsetail by animals has caused muscle weakness (Anon, 1991).

Laboratory Monitoring

Monitoring Parameters Levels

    4.1.1) SUMMARY
    A) No specific laboratory tests are necessary unless otherwise clinically indicated.
    B) Monitor vital signs and serum electrolytes in symptomatic patients.

Methods

    A) SPECTROMETRY/SPECTROSCOPY
    1) The UV spectroscopic examination of Equisetum methanol extract revealed caffeic acid in E. arvense(Hamon & Awang, 1992).
    2) CHROMATOGRAPHY
    a) Thin-layer chromatography has been used to identify E. arvense components (Hamon & Awang, 1992).

Treatment

Life Support

    A) Support respiratory and cardiovascular function.

Patient Disposition

    6.3.1) DISPOSITION/ORAL EXPOSURE
    6.3.1.1) ADMISSION CRITERIA/ORAL
    A) Patients who remain symptomatic despite treatment should be admitted.
    6.3.1.2) HOME CRITERIA/ORAL
    A) A patient with an inadvertent exposure, that remains asymptomatic can be managed at home.
    6.3.1.3) CONSULT CRITERIA/ORAL
    A) Consult a poison center or medical toxicologist for assistance in managing patients with severe toxicity or in whom the diagnosis is not clear.
    6.3.1.5) OBSERVATION CRITERIA/ORAL
    A) Patients with a deliberate overdose, and those who are symptomatic, need to be monitored for several hours. Patients that remain asymptomatic can be discharged.

Monitoring

    A) No specific laboratory tests are necessary unless otherwise clinically indicated.
    B) Monitor vital signs and serum electrolytes in symptomatic patients.

Oral Exposure

    6.5.1) PREVENTION OF ABSORPTION/PREHOSPITAL
    A) Toxicity is generally only associated with chronic exposure. Gastrointestinal decontamination is generally not indicated.
    6.5.2) PREVENTION OF ABSORPTION
    A) SUMMARY
    1) Toxicity has generally only been reported after chronic ingestion. Gastrointestinal decontamination is generally not indicated. It should be considered after very large exposures or when other potentially toxic coingestants are involved.
    B) ACTIVATED CHARCOAL
    1) CHARCOAL ADMINISTRATION
    a) Consider administration of activated charcoal after a potentially toxic ingestion (Chyka et al, 2005). Administer charcoal as an aqueous slurry; most effective when administered within one hour of ingestion.
    2) CHARCOAL DOSE
    a) Use a minimum of 240 milliliters of water per 30 grams charcoal (FDA, 1985). Optimum dose not established; usual dose is 25 to 100 grams in adults and adolescents; 25 to 50 grams in children aged 1 to 12 years (or 0.5 to 1 gram/kilogram body weight) ; and 0.5 to 1 gram/kilogram in infants up to 1 year old (Chyka et al, 2005).
    1) Routine use of a cathartic with activated charcoal is NOT recommended as there is no evidence that cathartics reduce drug absorption and cathartics are known to cause adverse effects such as nausea, vomiting, abdominal cramps, electrolyte imbalances and occasionally hypotension (None Listed, 2004).
    b) ADVERSE EFFECTS/CONTRAINDICATIONS
    1) Complications: emesis, aspiration (Chyka et al, 2005). Aspiration may be complicated by acute respiratory failure, ARDS, bronchiolitis obliterans or chronic lung disease (Golej et al, 2001; Graff et al, 2002; Pollack et al, 1981; Harris & Filandrinos, 1993; Elliot et al, 1989; Rau et al, 1988; Golej et al, 2001; Graff et al, 2002). Refer to the ACTIVATED CHARCOAL/TREATMENT management for further information.
    2) Contraindications: unprotected airway (increases risk/severity of aspiration) , nonfunctioning gastrointestinal tract, uncontrolled vomiting, and ingestion of most hydrocarbons (Chyka et al, 2005).
    6.5.3) TREATMENT
    A) SUPPORT
    1) Treatment is symptomatic and supportive.
    B) MONITORING OF PATIENT
    1) No specific laboratory tests are necessary unless otherwise clinically indicated.
    2) Monitor vital signs and serum electrolytes in symptomatic patients.

Enhanced Elimination

    A) LACK OF INFORMATION
    1) There is no information regarding the effectiveness of hemodialysis or hemoperfusion for the removal of horsetail from plasma.

Range Of Toxicity

Summary

    A) TOXICITY: A minimum toxic dose has not been established. Toxicity has only been reported after chronic use.
    B) THERAPEUTIC DOSE: Dosing of herbal preparations is highly dependent on a variety of factors such as growing and harvesting conditions, plant parts and extraction methods used, and the dosage form chosen by the manufacturer. Standardization to single constituent markers has proven unreliable. Since no official standards have been established to date to regulate the production of herbal medicines in the United States, dosage ranges must be employed as guidelines. CUT HERBS: 6 grams daily. COLD MACERATE: (2 grams herb soaked in 150 milliliters (mL) cold water for 10 to 12 hours) three times daily. FLUID EXTRACT: 1:1 (grams/mL): 2 mL three times daily. TINCTURE: 1:5 (grams/mL): 10 mL three times daily. MAXIMUM DAILY DOSE: 6 grams daily.

Therapeutic Dose

    7.2.1) ADULT
    A) GENERAL
    1) Dosing of herbal preparations is highly dependent on a variety of factors such as growing and harvesting conditions, plant parts and extraction methods used, and the dosage form chosen by the manufacturer. Standardization to single constituent markers has proven unreliable. Since no official standards have been established to date to regulate the production of herbal medicines in the United States, dosage ranges must be employed as guidelines.
    2) ORAL
    a) GENERAL USE
    1) Cut herbs: 6 grams daily (Blumenthal et al, 1998; Blumenthal et al, 2000).
    2) Cold Macerate: (2 grams herb soaked in 150 milliliters (mL) cold water for 10 to 12 hours) three times daily(Blumenthal et al, 2000).
    3) Decoction/Infusion: 2 grams cut herb combined with 150 mL water three times daily (preparation should be boiled for 5 minutes and allowed to steep for 10 to 15 minutes prior to administration) (Blumenthal et al, 2000).
    4) Fluid Extract, 1:1 (grams/mL): 2 mL three times daily(Blumenthal et al, 2000).
    5) Tincture, 1:5 (grams/mL): 10 mL three times daily(Blumenthal et al, 2000).
    6) MAXIMUM DAILY DOSE: 6 grams daily. Doses of the herb powder in excess of 5 grams daily should be taken with meals (McGuffin et al, 1997).
    7) TOPICAL
    a) SKIN INFLAMMATION/IRRITATION
    1) Bath Additive: 2 grams herb/liter hot bath water steeped for one hour prior to bathing(Blumenthal et al, 2000).
    2) Cataplasm/Compress: Boil 10 grams herb/liter water for 10 to 15 minutes and apply topically as a cataplasm or compress. A cataplasm is prepared as a semisolid paste of the horsetail decoction and applied as moist heat directly to the skin. A compress is prepared by saturating a cloth with the hot semisolid horsetail decoction and applied directly to the skin (Blumenthal et al, 2000; Blumenthal et al, 1998).
    7.2.2) PEDIATRIC
    A) GENERAL
    1) Pediatric dosing not available.

Pharmacology Toxicology

Pharmacologic Mechanism

    A) Mild diuretic, hemostyptic, vulnerary and mild leukocytosis causing actions have been reported in several sources(Blumenthal et al, 2000).

References

General Bibliography

    1) Anon: Horsetail. In: DerMarderosian A (ed). The Lawrence Review of Natural Products. , Facts and Comparisons , St Louis, MO, 1991.
    2) Blumenthal M, Busse WR, Goldberg A, et al: The Complete German Commission E Monographs , 1st. American Botanical Council, Austin, TX, 1998.
    3) Blumenthal M, Goldberg A, & Brinckmann J (Eds): Herbal Medicine, Expanded Commission E Monographs, 1st. Integrative Medicine Communications, Newton, MA, 2000.
    4) Chyka PA, Seger D, Krenzelok EP, et al: Position paper: Single-dose activated charcoal. Clin Toxicol (Phila) 2005; 43(2):61-87.
    5) D'Agostino M, Dini A, Pizza C, et al: Sterols from Equisetum arvense.. Boll Soc Ital Biol Sper 1984; 60(12):2241-2245.
    6) Elliot CG, Colby TV, & Kelly TM: Charcoal lung. Bronchiolitis obliterans after aspiration of activated charcoal. Chest 1989; 96:672-674.
    7) FDA: Poison treatment drug product for over-the-counter human use; tentative final monograph. FDA: Fed Register 1985; 50:2244-2262.
    8) Franck Bakke IL, Kringstad R, & Nordal A: Water-soluble acids from Equisetum arvense L.. Acta Pharm Suec 1978; 15(2):141-147.
    9) Ghassemi N & Ghanadi AR: 41st Annual Congress on Medicinal Plant Research. Dusseldorf, Germany, August 31-September 4, 1993.. Planta Med 1993; 59(7 Suppl):A638.
    10) Golej J, Boigner H, Burda G, et al: Severe respiratory failure following charcoal application in a toddler. Resuscitation 2001; 49:315-318.
    11) Graefe EU & Veit M: Urinary metabolites of flavonoids and hydroxycinnamic acids in humans after application of a crude extract from Equisetum arvense.. Phytomedicine 1999; 6(4):239-246.
    12) Graff GR, Stark J, & Berkenbosch JW: Chronic lung disease after activated charcoal aspiration. Pediatrics 2002; 109:959-961.
    13) Hamon NW & Awang DV: Horsetail. Can Pharm J 1992; 125:399-401.
    14) Harris CR & Filandrinos D: Accidental administration of activated charcoal into the lung: aspiration by proxy. Ann Emerg Med 1993; 22:1470-1473.
    15) Henderson JA, Evans EV, & McIntosh PA: The antithiamine action of Equisetum.. J Am Vet Med Assoc 1952; 120:375-378.
    16) Jellin JM, Gregory P, & Batz F: Pharmacist's letter/Prescriber's Letter Natural Medicines Comprehensive Database, 3rd ed, Therapeutic Research Faculty, Stockton, CA, 2000.
    17) Jones LR: Are our native horsetails or ferns poisonous?. Proc Soc Promotion Agr Sci 1901; 22:70-74.
    18) Kingsbury JM: Poisonous Plants of the United States and Canada., Prentice Hall, Englewood Cliffs, NJ, USA, 1964.
    19) Maeda H, Miyamoto K, & Sano T: Occurrence of dermatitis in rats fed a cholesterol diet containing field horsetail (Equisetum arvense L.).. J Nutr Sci Vitaminol 1997; 43(5):553-563.
    20) McGuffin M, Hobbs C, Upton R, et al (Eds): American Herbal Products Association's Botanical Safety Handbook. , CRC Press, Boca Raton, FL, USA, 1997.
    21) Miro O, Pedrol E, Nogue S, et al: Severe hyponatremia and hypopotassemia induced by the consumption of Equisetum telmateia.. Med Clin 1996; 106(16):639.
    22) Nitta A, Yoshida S, & Tagaeto T: A comparative study of crude drugs in Southeast Asia. X. Crude drugs derived from Equisetum species.. Chem Pharm Bull 1977; 25(5):1135-1139.
    23) None Listed: Position paper: cathartics. J Toxicol Clin Toxicol 2004; 42(3):243-253.
    24) Pollack MM, Dunbar BS, & Holbrook PR: Aspiration of activated charcoal and gastric contents. Ann Emerg Med 1981; 10:528-529.
    25) Rapp WF Jr: The toxicity of equisetum.. Am Fern J 1954; 44:148-154.
    26) Rau NR, Nagaraj MV, Prakash PS, et al: Fatal pulmonary aspiration of oral activated charcoal. Br Med J 1988; 297:918-919.
    27) Sudan BJ: Seborrhoeic dermatitis induced by nicotine of horsetails Equisetum arvense L.. Contact Dermatitis 1985; 13(3):201-202.
    28) Veit M & Stack D: EI-E-caffeoyl-meso-tartaric acid in the barren sprouts of Equisetum arvense.. Phytochemistry 1991; 302:527-529.