Drugs in Pregnancy and Lactation: Tenth Edition

PEPPERMINT

Herb

PREGNANCY RECOMMENDATION: Limited Human Data—Probably Compatible

BREASTFEEDING RECOMMENDATION: No Human Data—Probably Compatible

PREGNANCY SUMMARY

Peppermint and its oil have been used for hundreds of years. These products are available as teas, liquid extract, capsules, lozenges, throat sprays, flavorings, liniments, and inhalants. Several sources state that ingestion of large doses of peppermint/peppermint oil is unsafe in pregnancy because of possible emmenagogue and abortifacient effects. Although scientific documentation of increased uterine bleeding and abortion associated with peppermint/peppermint oil has not been located, high oral doses of menthol (e.g., 2–9 g) are considered lethal (1). However, this should not be concern for topical preparations and ingesting recommended doses of oral products. The absence in the medical literature of adverse reports involving a commonly used substance suggests that there is little risk from the typical use of this herb in pregnancy.

FETAL RISK SUMMARY

A variety of peppermint plants are cultivated in Europe and North America. Peppermint (Mentha x piperita) and its essential oil, first described in England in 1696, have been used in the treatment of cancers, colds, cramps, indigestion, nausea, sore throat, and toothaches (2). The plants contain 0.1%–1.5% essential oil (2,3). More than 100 compounds have been isolated from peppermint oil, but the primary pharmacologically active agents are menthol (29%–48%), menthone (20%–31%), and menthyl acetate (3%–10%), and lesser amounts of caffeic acid, flavonoids, and tannins (2). Menthol is a common ingredient in over-the-counter mouth and throat products and liniments.

The ingestion of large doses of peppermint or peppermint oil in pregnancy is considered by some reviewers to be unsafe because of a possible emmenagogue and abortifacient properties (1,2,46), but another source does not mention these effects (7). No original reports describing this toxicity have been located.

A 2000 review conducted an extensive search of the literature regarding the use of herbal products for nausea/vomiting of pregnancy (8). Finding little information in scientific and medical databases, the author continued the search in Web sites and the lay literature. From this source, the most commonly recommended herbs, all in the form of teas, were red raspberry leaf, ginger, peppermint, and chamomile (Roman and/or German). There were 33 sources recommending peppermint and 6 stating that it was unsafe in pregnancy. However, none of the sources provided scientific or clinical evidence to support their recommendations or warnings (8).

In a 2004 nonrandomized study conducted in Canada, 20 of 27 women (74%) experienced pregnancy-induced nausea/vomiting 10 of whom were being treated with herbal remedies (9). The herbal remedies were ginger (N = 3), ginger plus peppermint (N = 3), peppermint (N = 3), and cannabis (N = 1). Although the peak incidence of nausea/vomiting of pregnancy is usually in the 1st trimester, no information was given on the timing or quantity of the exposures or the outcomes of the pregnancies (9).

BREASTFEEDING SUMMARY

No reports describing the use of peppermint, peppermint oil, or menthol during lactation have been located. Peppermint and its oil have been used for hundreds of years. These products are available as teas, liquid extract, capsules, lozenges, throat sprays, flavorings, liniments, and inhalants. The absence in the medical literature of adverse reports involving a commonly used substance suggests that there is little risk to a nursing infant from the mother’s use of this herb during breastfeeding. Because infants may be sensitive to menthol (1,2), rubs and liniments containing menthol should not be applied to the mother’s breast or nipples.

References

1.Peppermint leaf. Peppermint oil. In Natural Medicines Comprehensive Database. 5th ed. Stockton, CA: Therapeutic Research Faculty, 2003:1028–9; 1029–31.

2.Peppermint. In The Review of Natural Products. Facts and Comparisons. St. Louis, MO: Wolters Kluwer Health, November 2006.

3.Charrois TL, Hrudey J, Garniner P, Vohra S. Peppermint oil. Pediatr Rev 2006;27:e49–51.

4.Ernst E. Herbal medicinal products during pregnancy: are they safe? Br J Obstet Gynaecol 2002;109:227–35.

5.Peppermint oil (Mentha x piperita L) Natural Standard Monograph 2007. Available at http://www.naturalstand.com. Accessed April 30, 2007.

6.Gallo M, Koren G, Smith MJ, Boon H. The use of herbal medicine in pregnancy and lactation. Koren G, ed. In Maternal–Fetal Toxicology. A Clinician’s Guide. 3rd ed. New York, NY: Marcel Dekker, 2001:583.

7.Peppermint leaf. Peppermint oil. Blumenthal M, ed. In The Complete German Commission E Monographs. Austin, TX: American Botanical Council, 1998:180–2.

8.Wilkinson JM. What do we know about herbal morning sickness treatments? A literature survey. Midwifery 2000;16:224–8.

9.Westfall RE. Use of anti-emetic herbs in pregnancy: women’s choices, and the question of safety and efficacy. Complement Ther Nurs Midwifery 2004;10:30–6.