Pennyroyal

American pennyroyal, European pennyroyal, lurk-in-the-ditch, Mentha pulegium, mosquito plant, piliolerial, pudding grass, pulegium, run-by-the-ground, squaw balm, squawmint, tickweed

The leaves and flowering tops of Mentha pulegium contain pennyroyal oil. The oil contains D-pulegione (60% to 90%), methone, isomethone, tannins, and flavonoids. Pulegione depletes glutathione in the liver. In high doses, it has abortifacient properties. Pennyroyal is available as a tea, tincture, loose dried herb, and capsules.

Reported uses

In the past, pennyroyal was used to treat digestive disorders, liver and gallbladder disorders, bowel disorders, pneumonia, gout, and colds. It’s currently used topically for skin diseases. It’s also used as an abortifacient, insect repellent, antiseptic, flavoring agent, and fragrance in detergents, soaps, and perfumes.

Administration

• Dried herb: 1 to 4 g by mouth three times a day
• Insect repellent: Applied sparingly to skin, as needed
• Tea: 1 cup by mouth every day.

Hazards

Adverse effects associated with the use of pennyroyal include lethargy, delirium, unconsciousness, seizures, hallucinations, hypertension, tachycardia, respiratory failure, anesthetic-like paralysis, shock, abdominal pain, nausea, vomiting, miscarriage, irreversible renal damage, hepatotoxicity, severe liver damage, and dermatitis. Herbal products that contain alcohol may cause a disulfiram-like reaction.

Safety Risk Severe poisoning has been reported after consumption of 5 g of pennyroyal oil as an abortifacient. Overdose may cause vomiting, hypertension, anesthetic-like paralysis, and respiratory failure.

Safety Risk Pennyroyal has toxic effects on the liver and isn’t recommended for internal use.

Clinical considerations

• Some products may contain alcohol and may not be suitable for use by children, alcoholic patients, patients with liver failure, or patients who take disulfiram or metronidazole.
• Caution patient about pennyroyal’s toxic effects on the liver and warn him to take herb orally only with close supervision by a health care provider.
• If patient uses the oil as a flavoring, warn him to use only small amounts.
• Advise pregnant patient not to use this herb because it has abortifacient properties.
• Warn patient to keep all herbal products away from children and pets.
• Tell patient to remind prescriber and pharmacist of any herbal and dietary supplement that he’s taking when obtaining a new prescription.
• Advise patient to consult his health care provider before using an herbal preparation because a treatment with proven efficacy may be available.

Research summary

The concepts behind the use of pennyroyal and the claims made regarding its effects haven’t yet been validated scientifically.