Horsetail : Safety

by MedlinePlus

(Page 2 of 2)

Allergies

People with allergies to E. arvense, related substances, or to nicotine should avoid horsetail. Rash has been reported in a patient taking horsetail who was known to be sensitive to nicotine.

Side Effects and Warnings

There are few scientific studies or reports of side effects with horsetail. It is more often used in Germany and Canada, where it is traditionally considered to be safe when taken in appropriate doses. E. palustre (marsh horsetail) contains a poisonous ingredient and should be avoided. There are reports that some batches of E. arvense (horsetail) have been contaminated with E. palustre .

Large doses of horsetail may cause symptoms of nicotine overdose, including fever, cold hands and feet, abnormal heart rate, difficulty walking, muscle weakness, and weight loss. People who smoke or who use nicotine patches or nicotine gum should avoid horsetail. Reports from animal studies and one report of a nicotine-allergic person describe a rash occurring after the use of white horsetail. Other reports from use in animals describe nausea, increased frequency of bowel movements, increased urination, loss of the body's potassium stores, and muscle weakness. People with kidney disorders should avoid horsetail.

Studies in mice suggest that horsetail may change the activity of the kidneys, causing abnormal control of the amount of water and potassium release. Low potassium, which in theory may occur with horsetail, can have negative effects on the heart. Individuals who have heart rhythm disorders or who take digoxin should be cautious. Studies suggest that horsetail does not change blood pressure. Other horsetail species have caused low blood sugar.

Horsetail contains an ingredient that destroys thiamine (vitamin B1), which could lead to deficiency with long-term use. This may cause permanent damage to the brain and nervous system, including confusion, difficulty walking, difficulties with vision and eye movement, and memory loss. People who have thiamine (vitamin B1) deficiency or poor nutrition should avoid horsetail, as it may affect levels of thiamine even more. Alcoholic or malnourished individuals are often thiamine deficient and this may be worsened by horsetail.

Avoid use in children due to anecdotal reports of poisonings while using horsetail stems as whistles.

Pregnancy and Breastfeeding

Horsetail is not recommended during pregnancy or breastfeeding, since little information is available about its safety. Its potential to cause thiamine (vitamin B1) depletion, low potassium, and nicotine-like effects are of particular concern. Many tinctures contain high levels of alcohol, and should be avoided during pregnancy.

Interactions

Interactions with Drugs

Some diuretic drugs ("water pills") can cause the body to lose water and potassium, for example loop diuretics like furosemide (Lasix®). The use of horsetail with certain diuretics may cause dehydration or further potassium deficiency. Some steroids and laxative drugs can also lower potassium levels and should not be combined with horsetail. Individuals with heart rhythm disorders who are treated withdigoxin (Lanoxin®)or digitoxin may be especially sensitive to low potassium levels, and potassium levels should be monitored in such individuals. Because horsetail can stimulate the brain and nervous system, caution should be used when combining horsetail with stimulant drugs. Other horsetail species have caused low blood sugar and therefore may increase effects ofdiabetes medications.

Many tinctures contain high levels of alcohol, and may cause nausea or vomiting when taken with metronidazole (Flagyl®) or disulfiram (Antabuse®).

Interactions with Herbs and Dietary Supplements

Increased urine production, dehydration, or electrolyte imbalances may theoretically occur when horsetail is used with herbs that may increase urination (diuretic herbs). Examples include artichoke, celery, corn silk, couchgrass, dandelion, elder flower, juniper berry, kava, shepherd's purse, uva ursi, and yarrow. Dehydration or low potassium levels theoretically may occur if horsetail is used with laxative agents. Possible laxative herbs include alder buckthorn, aloe dried leaf sap, black root, blue flag rhizome, butternut bark, dong quai, European buckthorn, eyebright, cascara bark, castor oil, chasteberry, colocynth fruit pulp, dandelion, gamboges bark, jalap root, manna bark, plantain leaf, podophyllum root, psyllium, rhubarb, senna, wild cucumber fruit, and yellow dock root.

In theory, low potassium levels caused by horsetail may be dangerous in people using herbs that havecardiac glycosideactivity on the heart. Herbs with possible cardiac glycoside activity include adonis, balloon cotton, black hellebore root/melampode, black Indian hemp, bushman's poison, Cactus grandifloris , convallaria, eyebright, figwort, foxglove/digitalis, frangipani, hedge mustard, hemp root/Canadian hemp root, king's crown, lily-of-the-valley, motherwort, oleander leaf, pheasant's eye plant, plantain leaf, pleurisy root, psyllium husks, redheaded cotton-bush, rhubarb root, rubber vine, sea-mango, senna fruit, squill, strophanthus, uzara, wallflower, wintersweet, yellow dock root, and yellow oleander.

Horsetail may break downthiamineand may cause thiamine deficiency. This has been reported only in animals, and there are no reliable reports of this interaction in humans. Other horsetail species have caused low blood sugar and therefore may increase effects of herbs and supplements that also lowerblood sugar levels.

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