Pennyroyal : Safety, Interactions

by MedlinePlus

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Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Allergic reactions to pennyroyal or to its components, including pulegone, may occur, although there are no reliable published reports.

Side Effects and Warnings

Pennyroyal herb and volatile oils have been associated with multiple reports of toxicity and adverse effects, including seizures, loss of consciousness, and death. In animals, pennyroyal (taken by mouth or placed on the skin) has been associated with liver, lung, and brain toxicity. Doses greater than 10 milliliters of pennyroyal may be associated with death. Cases of human overdose and death have been reported in infants, children, and adults.

Pennyroyal oil toxicity may cause nausea, vomiting, abdominal pain, burning in the throat, difficulty swallowing, diarrhea, excessive sweating, chills, fever, headache, ringing in the ears, dizziness, extreme thirst, muscle spasms, restlessness, tremor, excessive talkativeness, hallucinations, agitation, drowsiness, fatigue, confusion, mania, seizures, organ failure (brain, liver, lung, kidney, heart), altered (low or high) heart rate, altered (low or high) blood pressure, slow breathing, coma, loss of consciousness, and death. Typically, the first symptoms of poisoning, from either pennyroyal oil or pennyroyal leaves, occur in the stomach and bowels, and are often apparent soon after ingestion. Symptoms in pennyroyal overdose may mimic that of acetaminophen (Tylenol®) overdose, and the use of N-acetylcysteine (an antidote used for acetaminophen toxicity) treatment may prove beneficial.

Other side effects may include contact dermatitis, rash (when placed on the skin), malaise, lethargy, agitation, abnormal sensations, or change (increase or decrease) in pupil size. There are reports that pennyroyal may cause abortion. Pennyroyal has been used historically as an emmenagogue (menstrual stimulant) and may cause menstrual bleeding. There are reports that large amounts of pennyroyal may be irritating to the urinary tract. Pennyroyal may cause hypoglycemia (low blood sugar), hemolytic anemia (low red blood cell count due to destruction of cells), disseminated intravascular coagulation (widespread abnormal clotting and/or bleeding), and metabolic acidosis.

Pregnancy and Breastfeeding

Pennyroyal is not recommended during pregnancy or breastfeeding, due to the risk of uterine contractions, stimulation of menstruation, and abortion.

Many tinctures contain high levels of alcohol, and should be avoided during pregnancy.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

Interactions with Drugs

In theory, the toxicity of pennyroyal may be increased when combined with acetaminophen (Tylenol®): pennyroyal may lower a liver substance (glutathione), which may increase the risk of acetaminophen toxicity. Based on animal and human cases, pennyroyal may cause increased risk of liver damage caused by other drugs.

Based on animal research, pennyroyal may interfere with the way the body processes certain drugs using the liver's "cytochrome P450" enzyme system. As a result, the levels of these drugs may be increased in the blood, and may cause increased effects or potentially serious adverse reactions. If you are using any medications, check the package insert and speak with your healthcare provider or pharmacist about possible interactions.

Based on human cases, pennyroyal may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. Patients taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare provider. Medication adjustments may be necessary. Based on animal research, pennyroyal may have antihistamine effects, and may cause increased effects if combined with drugs that have antihistamine action such as diphenhydramine (Benadryl®), fexofenadine (Allegra®), or loratidine (Claritin®).

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

Based on animal and human cases, pennyroyal may increase the risk of liver damage when combined with some herbs or supplements. Examples of other herbs that may damage the liver include: Ackee, bee pollen, birch oil, blessed thistle, borage, bush tea, butterbur, chaparral, coltsfoot, comfrey, DHEA, Echinacea purpurea , Echium spp., germander, Heliotropium spp., horse chestnut, Jin-bu-huan ( Lycopodium serratum ), kava, lobelia, L-tetrahydropalmatine (THP), mate, niacin (vitamin B-3), niacinamide, Paraguay tea, periwinkle, Plantago lanceolata , pride of Madeira, rue, sassafras, scullcap, Senecio spp./groundsel, tansy ragwort, turmeric/curcumin, Tu-san-chi ( Gynura segetum ), uva ursi, valerian, and white chameleon.

Based on animal research, pennyroyal may interfere with the way the body processes certain herbs or supplements using the liver's "cytochrome P450" enzyme system. As a result, the levels of these herbs or supplements may be increased in the blood, and may cause increased effects or potentially serious adverse reactions. It may also alter the effects that other herbs or supplements possibly have on the P450 system, such as bloodroot, cat's claw, chamomile, chaparral, chasteberry, damiana, Echinacea angustifolia , goldenseal, grapefruit juice, licorice, oregano, red clover, St. John's wort, wild cherry, and yucca. If you are using any medications, check the package insert and speak with your healthcare provider or pharmacist about possible interactions.

Based on human cases, pennyroyal may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Possible examples include: Aloe vera , American ginseng, bilberry, bitter melon, burdock,fenugreek, fish oil, gymnema, horse chestnut seed extract (HCSE), marshmallow, milk thistle, Panax ginseng, rosemary, Siberian ginseng, stinging nettle and white horehound.

Pennyroyal and black cohosh have been taken together to induce abortion, and this combination has been associated with toxicity and death. Pennyroyal and blue cohosh have traditionally been taken together to normalize the menstrual cycle in women. In theory, the combination of the two herbs may act together to increase menstrual flow. Notably, blue cohosh has been associated with multiple dangerous effects including stroke.

Based on human study, pennyroyal may reduce the body's ability to absorb iron in meals by up to 75%.

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