Red Clover - Plan B (Levonorgestrel) Interaction

Interaction Details

Levonorgestrel is classified as belonging to the following category: Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, red clover might increase levels of drugs metabolized by CYP3A4; however, a small clinical study found no effect.
In vitro evidence shows that red clover might inhibit CYP3A4 isoenzymes. However, a clinical study in healthy postmenopausal individuals shows that taking red clover capsules standardized to contain 60 mg isoflavones twice daily for 14 days does not affect the pharmacokinetics of alprazolam, a CYP3A4 probe substrate.

Interaction Rating

Likelihood of Occurrence

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

References

• 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.
• Unger M, Frank A. Simultaneous determination of the inhibitory potency of herbal extracts on the activity of six major cytochrome P450 enzymes using liquid chromatography/mass spectrometry and automated online extraction. Rapid Commun Mass Spectrom 2004;1
• Chen L, Choi J, Leonard SW, et al. No Clinically Relevant Pharmacokinetic Interactions of a Red Clover Dietary Supplement with Cytochrome P450 Enzymes in Women. J Agric Food Chem. 2020;68(47):13929-13939.

Levonorgestrel Overview

• 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.

Red Clover - More Interactions

Red Clover interacts with 844 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.