Oregon Grape - Plan B (Levonorgestrel) Interaction
Herbal: Oregon Grape
Also Known As: Mahonia aquifolium, Barberry, Berberis, Blue Barberry, Creeping Barberry, Holly Barberry, Holly Mahonia, Holly-Leaved Berberis, Mahonia, Mahonia Faux Houx, Mahonia à Feuilles de Houx, Mahonie, Mountain-Grape, Oregon Barberry, Oregon Grape-Holly, Scraperoot
Drug: Levonorgestrel
Brand names:
Plan B, Mirena, Levonelle One Step, Levonelle 1500, Norgeston, Skyla, Liletta, Kyleena
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
May 25, 2025
Interaction Details
Levonorgestrel is classified as belonging to the following category: Cytochrome P450 3A4 (Cyp3A4) Substrates
Theoretically, Oregon grape might increase serum levels of drugs metabolized by CYP3A4.
In vitro research and preliminary clinical evidence suggest that berberine, a constituent of Oregon grape, moderately inhibits cytochrome P450 3A4 (CYP3A4).
Interaction Rating
Likelihood of Occurrence
PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
References
- Wu X, Li Q, Xin H, Yu A, Zhong M. Effects of berberine on the blood concentration of cyclosporin A in renal transplanted recipients: clinical and pharmacokinetic study. Eur J Clin Pharmacol 2005;61:567-72.
- Budzinski JW, Foster BC, Vandenhoek S, Arnason JT. An in vitro evaluation of human cytochrome P450 3A4 inhibition by selected commercial herbal extracts and tinctures. Phytomedicine 2000;7:273-82.
- Guo, Y., Chen, Y., Tan, Z. R., Klaassen, C. D., and Zhou, H. H. Repeated administration of berberine inhibits cytochromes P450 in humans. Eur J Clin Pharmacol 2012;68(2):213-217.
- Hermann, R. and von, Richter O. Clinical evidence of herbal drugs as perpetrators of pharmacokinetic drug interactions. Planta Med 2012;78(13):1458-1477.
Oregon Grape Overview
Oregon grape (Mahonia aquifolium) is a perennial shrub that is native to the Pacific Northwest region of the United States, including Oregon and Washington. It is also found in parts of Canada. The plant is a member of the barberry family (Berberidaceae) and is closely related to the holly plant.
Oregon grape is often grown as an ornamental plant due to its attractive foliage and colorful berries. It is also used medicinally and is believed to have astringent, tonic, and anti-inflammatory properties. The root of the plant is used to make a herbal extract that is used to treat a variety of ailments, including skin conditions, digestive problems, and respiratory conditions. Most of the positive evidence for a medicinal effect is with topical applications as some research has shown topical preparations may modestly decrease the severity of psoriasis. It is important to note that the berries of the plant can be somewhat bitter and may contain toxins, so they should be eaten in moderation.
Levonorgestrel Overview
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Levonorgestrel is used to prevent pregnancy after unprotected sexual intercourse (sex without any method of birth control or with a birth control method that failed or was not used properly [e.g., a condom that slipped or broke or birth control pills that were not taken as scheduled]). Levonorgestrel should not be used to prevent pregnancy on a regular basis. This medication is to be used as an emergency contraceptive or backup in case regular birth control fails or is used incorrectly. Levonorgestrel is in a class of medications called progestins. It works by preventing the release of an egg from the ovary or preventing fertilization of the egg by sperm (male reproductive cells). It also may work by changing the lining of the uterus (womb) to prevent development of a pregnancy. Levonorgestrel may prevent pregnancy, but it will not prevent the spread of human immunodeficiency virus (HIV, the virus that causes acquired immunodeficiency syndrome [AIDS]) and other sexually transmitted diseases.
Oregon Grape - More Interactions
Oregon Grape interacts with 1189 drugs
Interaction Rating Key
These severity listings are for informational use only. Never start, stop or otherwise change your therapy before speaking with your provider.
| Major | The combined use of these agents is strongly discouraged as serious side effects or other negative outcomes could occur. |
| Moderate | Use cautiously under the care of a healthcare professional or avoid this combination. A significant interaction or negative outcome could occur. |
| Minor | Be aware that there is a chance of an interaction. Watch for warning signs of a potential interaction. |
| Unknown | No interactions have been reported or no interaction data is currently available. |
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Parts of this content are provided by the Therapeutic Research Center, LLC.
DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.
© 2021 Therapeutic Research Center, LLC
Drug descriptions are provided by MedlinePlus.
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Dr. Brian Staiger, PharmD
In addition to being a clinical pharmacist specializing in pharmacotherapy, Dr. Brian Staiger is a registered herbalist through the American Herbalist Guild. He has combined his passion for pharmacy practice with the study of medical ethnobotany to improve patient care. Feel free to reach out about any of your herbal or medication questions!
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