Mentha pulegium L.

Pennyroyal/Drug Interactions:

  • AbortifacientsAbortifacients: Traditionally, pennyroyal is considered to be an abortifacient, and it has been historically used to induce abortions. Case reports suggest that the essential oil of pennyroyal may function as an abortifacient (11; 12) and emmenagogue (1; 13; 14). Although pennyroyal oil has been historically used to induce abortions, it typically does so at lethal or near-lethal doses, making this action unpredictable, dangerous, and not recommended.
  • AntiandrogensAntiandrogens: Traditionally, pennyroyal is considered to be an abortifacient and an emmenagogue. Case reports suggest that the essential oil of pennyroyal may function as an abortifacient (11; 12) and emmenagogue (1; 13; 14).
  • AntibioticsAntibiotics: In vitro, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Klebsiella sp isolates to essential oil of Mentha pulegium were 1.9x10-3 to 4.9x10-4 mm3 (15).
  • AntiestrogensAntiestrogens: Traditionally, pennyroyal is considered to be an abortifacient and an emmenagogue. Case reports suggest that the essential oil of pennyroyal may function as an abortifacient (11; 12) and emmenagogue (1; 13; 14).
  • Acetaminophen (Tylenol?)Acetaminophen (Tylenol?): The toxicity of pennyroyal may theoretically be increased when combined with acetaminophen. Acetaminophen may induce hepatotoxicity when glutathione stores are depleted, and there are data to suggest that pennyroyal may also deplete hepatic glutathione stores (42; 43).
  • AntidiabeticsAntidiabetics: There are two case reports of hypoglycemia in pediatric patients after ingesting pennyroyal (3).
  • AntihistaminesAntihistamines: Pulegone, a constituent of pennyroyal, has been shown to exert antihistamine effects on guinea-pig ileum (44).
  • AntineoplasticsAntineoplastics: In vitro, the methanolic extract of Mentha pulegium had anti-genotoxic effects as determined by the sister chromatid exchange method (16).
  • Cytochrome P450 metabolized agentsCytochrome P450 metabolized agents: Due to the suggested inhibition of the P450system by pennyroyal, concomitant use with drugs metabolized by the P450system may increase serum levels of those drugs. Similarly, pennyroyal levels may be affected by agents altering the P450 system. In vivo and in vitro studies suggest that the pennyroyal constituent pulegone diminishes the function of rat liver cytochrome P450 in an irreversible, time dependent fashion (32). In vitro and in vivo research suggests that the pulegone metabolite menthofuran is a potent inhibitor of human liver CYP2A6 (45) and may account for a significant degree of pennyroyal's hepatotoxic effects (33; 34). Pulegone and menthofuran may deplete cellular glutathione levels, leaving hepatocytes vulnerable to free radical damage (35).
  • Disulfiram (Antabuse?)Disulfiram (Antabuse?): According to secondary sources, many tinctures contain high levels of alcohol and may cause nausea or vomiting when taken with metronidazole (Flagyl?) or disulfiram (Antabuse?).
  • Drugs that may lower seizure thresholdDrugs that may lower seizure threshold: Based on tradition, pennyroyal essential oil may have epileptogenic properties due to its constituents, namely its highly reactive monoterpene ketones (40).
  • Fertility agentsFertility agents: Traditionally, pennyroyal is considered to be an abortifacient, and it has been historically used to induce abortions. Case reports suggest that the essential oil of pennyroyal may function as an abortifacient (11; 12) and emmenagogue (1; 13; 14).
  • HepatotoxinsHepatotoxins: An autopsy from an overdose found massive hepatic necrosis (4). Chemical hepatitis has been reported and is often detectable within 24 hours of ingestion of pennyroyal (4). Pulegone, a constituent of pennyroyal, has caused increased transaminases in humans (3) and increased plasma alkaline phosphatase and liver weight in rats after 28 days (160mg/kg) (38).
  • Hormonal agentsHormonal agents: Traditionally, pennyroyal is considered to be an abortifacient and an emmenagogue. Case reports suggest that the essential oil of pennyroyal may function as an abortifacient (11; 12) and emmenagogue (1; 13; 14).
  • Insect repellentsInsect repellents: Mentha pulegium extract showed moderate repellence against Amblyomma cajennense (Acari: Ixodidae) nymphs (18) and Mentha pulegium essential oil and its benzyl alcohol showed good repellence against Pediculus humanus capitis (75.5% and 57.8%, respectively) (19).
  • Metronidazole (Flagyl?)Metronidazole (Flagyl?): According to secondary sources, many tinctures contain high levels of alcohol and may cause nausea or vomiting when taken with metronidazole (Flagyl?) or disulfiram (Antabuse?).

    • Pennyroyal/Herb/Supplement Interactions:

  • AbortifacientsAbortifacients: Traditionally, pennyroyal is considered to be an abortifacient, and it has been historically used to induce abortions. Case reports suggest that the essential oil of pennyroyal may function as an abortifacient (11; 12) and emmenagogue (1; 13; 14). Although pennyroyal oil has been historically used to induce abortions, it typically does so at lethal or near-lethal doses, making this action unpredictable, dangerous, and not recommended.
  • AntiandrogenicsAntiandrogenics: Traditionally, pennyroyal is considered to be an abortifacient and an emmenagogue. Case reports suggest that the essential oil of pennyroyal may function as an abortifacient (11; 12) and emmenagogue (1; 13; 14).
  • AntibacterialsAntibacterials: In vitro, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Klebsiella sp isolates to essential oil of Mentha pulegium were 1.9x10-3 to 4.9x10-4 mm3 (15).
  • AntiestrogensAntiestrogens: Traditionally, pennyroyal is considered to be an abortifacient and an emmenagogue. Case reports suggest that the essential oil of pennyroyal may function as an abortifacient (11; 12) and emmenagogue (1; 13; 14).
  • AntineoplasticsAntineoplastics: In vitro, the methanolic extract of Mentha pulegium had anti-genotoxic effects as determined by the sister chromatid exchange method (16).
  • AntioxidantsAntioxidants: In vitro, various forms of Mentha pulegium had antioxidant effects (16; 46).
  • Black cohoshBlack cohosh: According to secondary sources, pennyroyal and black cohosh (Cimicifuga racemosa) are sometimes taken together to induce abortion, although the use of these herbs together cannot be recommended due to the possibility of increased toxicity and death. There is a case report of a 24 year-old woman who took 48-56% of pennyroyal herb in an alcohol base and an unknown amount of black cohosh root for two weeks in an attempt to induce abortion (1). Following a single subsequent dose of this combination, the patient died within 48 hours.
  • Blue cohosh (Caulophyllum thalictroides)Blue cohosh (Caulophyllum thalictroides): According to secondary sources, pennyroyal and blue cohosh (Caulophyllum thalictroides) have traditionally been taken together to normalize the menstrual cycle in women, and thus may act synergistically to increase menstrual flow. This use has not been scientifically investigated. Notably, blue cohosh may act as a vasoconstrictor and has been associated with multiple adverse outcomes.
  • Cytochrome P450 metabolized agentsCytochrome P450 metabolized agents: Due to the suggested inhibition of the P450system by pennyroyal, concomitant use with drugs metabolized by the P450system may increase serum levels of those drugs. Similarly, pennyroyal levels may be affected by agents altering the P450 system. In vivo and in vitro studies suggest that the pennyroyal constituent pulegone diminishes the function of rat liver cytochrome P450 in an irreversible, time dependent fashion (32). In vitro and in vivo research suggests that the pulegone metabolite menthofuran is a potent inhibitor of human liver CYP2A6 (45) and may account for a significant degree of pennyroyal's hepatotoxic effects (33; 34). Pulegone and menthofuran may deplete cellular glutathione levels, leaving hepatocytes vulnerable to free radical damage (35).
  • Hepatotoxic agentsHepatotoxic agents: An autopsy from an overdose found massive hepatic necrosis (4). Chemical hepatitis has been reported and is often detectable within 24 hours of ingestion of pennyroyal (4). Pulegone, a constituent of pennyroyal, has caused increased transaminases in humans (3) and increased plasma alkaline phosphatase and liver weight in rats after 28 days (160mg/kg) (38).
  • Hormonal herbs and supplementsHormonal herbs and supplements: Traditionally, pennyroyal is considered to be an abortifacient and an emmenagogue. Case reports suggest that the essential oil of pennyroyal may function as an abortifacient (11; 12) and emmenagogue (1; 13; 14).
  • Hormone replacement therapy (HRT)Hormone replacement therapy (HRT): Traditionally, pennyroyal is considered to be an abortifacient and an emmenagogue. Case reports suggest that the essential oil of pennyroyal may function as an abortifacient (11; 12) and emmenagogue (1; 13; 14).
  • HypoglycemicsHypoglycemics: The available scientific literature reports two cases of hypoglycemia in pediatric patients after ingesting pennyroyal (3).
  • IronIron: Pennyroyal has been found to inhibit the absorption of iron in meals by up to 75% (47).
  • Licorice (Glycyrrhiza glabra)Licorice (Glycyrrhiza glabra): In a 1961 case report, a 23 year-old woman, six weeks pregnant, was noted to experience a severe psychotic episode and seizures after ingesting an unknown dose of pennyroyal 3-4 times daily and "Widow Welch's Female Pills," a combination of ferrous sulfate, sulfur, licorice (Glycyrrhiza glabra), and turmeric (Curcuma longa) (22). The patient recovered two days following hospital admission without recurrence, and she delivered a healthy child.
  • N-acteylcysteineN-acteylcysteine: N-acetylcysteine was used as part of an effective treatment for pennyroyal oil consumption (7; 8); however, results from animal studies concluded that N-acetylcysteine did not afford a significant survival benefit in pennyroyal oil toxicity (9; 10).
  • Seizure threshold-lowering agentsSeizure threshold-lowering agents: Based on tradition, pennyroyal essential oil may have epileptogenic properties due to its constituents, namely its highly reactive monoterpene ketones (40).
  • Turmeric (Curcuma longa)Turmeric (Curcuma longa): In a 1961 case report, a 23 year-old woman, six weeks pregnant, was noted to experience a severe psychotic episode and seizures after ingesting an unknown dose of pennyroyal 3-4 times daily and "Widow Welch's Female Pills," a combination of ferrous sulfate, sulfur, licorice (Glycyrrhiza glabra), and turmeric (Curcuma longa) (22). The patient recovered without recurrence two days after she was admitted to the hospital, and she delivered a healthy child.

    • Pennyroyal/Food Interactions:

  • Insufficient available evidence.

    • Pennyroyal/Lab Interactions:

  • Liver function tests (LFTs)Liver function tests (LFTs): Hepatic toxicity due to the pennyroyal constituent pulegone has been associated with elevations in transaminases in rats (38) and humans (4; 3).
  • Serum glucoseSerum glucose: The available scientific literature reports two cases of hypoglycemia in pediatric patients after ingesting pennyroyal (3).