St. John's wort (hypericum perforatum) is one of the five best-selling herbs in the United States. It is used by many to treat the symptoms of depression, and many prefer it to prescription medications such as Paxil® and Zoloft. However, the herb has been the subject of growing concern about its interaction with birth control pills, the blood thinner warfarin, and cyclosporin, a medication used with those who have received organ transplants. A new study examining its effect on pregnant women and those who are breastfeeding contributes to the evidence that the product should be used with caution.
The new study, entitled "St. John's Wort (hypericum perforatum): Is It Safe During Pregnancy, Breastfeeding and With Prescription Medications? A Systematic Review," will soon be published in the Canadian Journal of Clinical Pharmacology. It is one in a series that systematically reviews the evidence relating to the safety of herbs commonly used during pregnancy and lactation.
The aim of the study was to systematically review the literature for evidence on the use, safety, and pharmacology of St. John's wort focusing on issues pertaining to pregnancy and lactation. The investigators searched seven databases for reports relating to the herb. The databases included AMED, CINAHL, Cochrane CENTRAL, Cochrane Library, MedLine, Natural Database, and Natural Standard. Each database was examined in duplicate for data from its inception. Unpublished research and bibliographies were also included. Data were compiled according to the grade of evidence found.
The researchers found varying levels of scientific evidence on the efficacy of use for different conditions; low-level evidence of harm during pregnancy; and strong evidence of side effects during lactation. As St. John's wort interacts with a number of medications due to its effect on cytochrome P450 enzymes, this may account for some of the findings.
The researchers concluded:
§ Caution is warranted when using St. John's wort during pregnancy and lactation.
§ St. John's wort may interact with medications prescribed during pregnancy.
§ During pregnancy, a case study and some animal studies reported lower birth weights with use of St. John's wort.
§ Strong scientific evidence showed that St. John's wort consumption during lactation did not affect maternal milk production nor affect infant weight, but may cause colic, drowsiness or lethargy.
§ St. John's wort showed strong scientific evidence of being an effective aid in combating mild to moderate depression and low-level evidence for other conditions.
The authors urge women not to assume that because herbs are labeled "natural" that they are safe. They recommend all pregnant and lactating women consult a licensed, health care professional before consuming any herb or medicine in general, and St. John's wort in particular. Finally, they recommend that any woman experiencing depression let their physician know immediately.