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Female Health | St. Johnís Wort Decreases Efficacy of Birth Control Pills

St. Johnís Wort Decreases Efficacy of Birth Control Pills

February 14, 2002óA new warning has been issued by Swedenís Medical Products Agency that St. Johnís wort may interfere with the effectiveness of birth control pills. This caution is the result of two reports from women who became pregnant while concurrently taking oral contraceptives and products that contained St. Johnís wort.

St. Johnís wort (Hypericum perforatum) has had the focus of the medical community in the past few years following several case reports regarding potential interactions with prescription medications. St. Johnís wort may activate enzymes in the liver responsible for breaking down certain drugs, thereby causing a decrease in the blood level of these drugs.1 If blood levels fall too low, the drug may fail to have the intended action. Previous reports have suggested that St. Johnís wort interferes with a drug used to prevent rejection of organ transplants (cyclosporine),2 heart medication (digoxin),3 antidepressants (Paxilģ and Zoloftģ),4 5 a blood thinner (warfarin),6 asthma medication (theophylline),7 and a drug used to treat people with HIV (indinavir).8

A previous report described eight women who experienced abnormal menstrual bleeding while taking St. Johnís wort and oral contraceptive pills.9 However, only three of these women returned to a normal menstrual cycle after discontinuing the herb, indicating that other unidentified factors may have contributed to the abnormal menstrual changes. It is unknown in both the previous and current reports whether St. Johnís wort lowers blood levels of the hormones in birth control pills, or whether it interferes in some other way with the action of these hormones.

The Swedish Medical Products Agency makes clear that the intention of this warning is not to discourage use of St. Johnís wort, but rather to educate consumers about potential drug interactions. St. Johnís wort has been shown to be an effective treatment for mild to moderate depression and may have some benefit for seasonal affective disorder (SAD).10 11 Although the interaction between St. Johnís wort and birth control pills has not been proven conclusively, the agency suggests that the effectiveness of oral contraceptive pills may decrease as previously reported with other prescription medications. Any woman taking an oral contraceptive should consult a physician before starting St. Johnís wort or other herbal therapy.


1. Nebel A, Schneider BJ, Baker RK, Kroll DJ. Potential metabolic interaction between St. Johnís wort and theophylline. Ann Pharmacother 1999;33:502.
2. Ernst E. Second thoughts about safety of St. Johnís wort. Lancet 1999;354:2014Ė6.
3. Johne A, Brockmöller J, Bauer S, et al. Pharmacokinetic interaction of digoxin with an herbal extract from St. Johnís wort (Hypericum perforatum). Clin Pharmacol Ther 1999;66:338Ė45.
4. Lantz MS, Buchalter E, Giambanco V. St. Johnís wort and antidepressant drug interactions in the elderly. J Geriatr Psychiatry Neurol 1999;12:7Ė10.
5. Gordon JB. SSRIís and St. Johnís wort: possible toxicity? Am Fam Physician 1998;57:950.
6. Ernst E. Second thoughts about safety of St. Johnís wort. Lancet 1999;354:2014Ė6.
7. Nebel A, Schneider BJ, Baker RK, Kroll DJ. Potential metabolic interaction between St. Johnís wort and theophylline. Ann Pharmacother 1999;33:502.
8. Piscitelli SC, Burstein AH, Chaitt D, et al. Indinavir concentrations and St. Johnís wort. Lancet 2000;355:547Ė8.
9. Safety of St. Johnís wort (Hypericum perforatum). Lancet 2000;355:575Ė7 [letters to the editor from various authors]. 10. Linde K, Ramirez G, Mulrow CD, et al. St. Johnís wort for depression-An overview and meta-analysis of randomized clinical trials. Br Med J 1996;313:253Ė8.
11. Martinez B, Kasper S, Ruhrmann S, Moller HJ. Hypericum in the treatment of seasonal affective disorders. J Geriatr Psychiatry Neurol 1994;7 Suppl 1:S29ĖS33.

Learn more about the services provided by Bastyr Center for Natural Health, or schedule your appointment today.

Darin Ingels, ND, MT (ASCP), received his bachelorís degree from Purdue University and his Doctorate of Naturopathic Medicine from Bastyr University in Kenmore, WA. Dr. Ingels is the author of Garlic and Cholesterol: Everything You Need to Know (Prima, 1999) and Natural Treatments for High Cholesterol (Prima, 2000). He currently is in private practice in Westport, CT, where he specializes in environmental medicine and allergies. Dr. Ingels is a regular contributor to Healthnotes and Healthnotes Newswire.

Copyright © 2002 Healthnotes, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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