Tamoxifen with Ipriflavone Interaction Details
Brand Names Associated with Tamoxifen
- Nolvadex®
- Soltamox®
- Tamoxifen
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Dec 18, 2023
Interaction Effect
Decreased tamoxifen effectiveness
Interaction Summary
In mice, dietary genistein negated the beneficial effects of tamoxifen. Since the plasma concentration obtained in mice was similar to that obtained when humans use genistein supplements, it is thought that a similar effect will occur in humans. Postmenopausal patients with estrogen-responsive breast cancer taking tamoxifen should be advised to avoid genistein supplements until a safe dietary level of genistein is determined. Caution is advised for ipriflavone. Although it has not been studied for an interaction with tamoxifen, it is closely related to genestein.
Severity
Major
Onset
Rapid
Evidence
Theoretical
How To Manage Interaction
Counsel postmenopausal patients to avoid use of ipriflavone while taking tamoxifen therapy for estrogen responsive breast cancer. Use alernative agents to manage side effects of tamoxifen.
Mechanism Of Interaction
Genestein acts as an estrogen agonist and may compete with tamoxifen for binding to alpha and beta estrogen receptors; ipriflavone is also an isoflavone with estrogenic effects
Literature Reports
A) In mice, dietary genistein negated the beneficial effects of tamoxifen. Mice received an estradiol implant plus tamoxifen (2.5 milligrams (mg) or 5 mg) with a genistein-free diet, or the implant with tamoxifen (2.5 mg or 5 mg) plus a diet containing 1000 parts per million genistein, or nothing (control). Genistein-fed mice had larger tumor sizes, increased estrogen-responsive gene (pS2, PR, and cyclin D1) expression and reduced plasma estradiol levels (p less than 0.05 for all findings). The authors concluded that caution is warranted when isoflavone supplements are taken by postmenopausal women on tamoxifen therapy for estrogen-responsive breast cancer .
Tamoxifen Overview
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Tamoxifen is used to treat breast cancer that has spread to other parts of the body in men and women. It is used to treat early breast cancer in women who have already been treated with surgery, radiation, and/or chemotherapy. It is used to reduce the risk of developing a more serious type of breast cancer in women who have had ductal carcinoma in situ (DCIS; a type of breast cancer that does not spread outside of the milk duct where it forms) and who have been treated with surgery and radiation. It is used to reduce the risk of breast cancer in women who are at high risk for the disease due to their age, personal medical history, and family medical history.
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Tamoxifen is in a class of medications known as antiestrogens. It blocks the activity of estrogen (a female hormone) in the breast. This may stop the growth of some breast tumors that need estrogen to grow.
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Definitions
Severity Categories
Contraindicated
These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.
Major
This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.
Moderate
This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.
Minor
While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.
Onset
Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.
Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.
Evidence
Level of documentation of the interaction.
Established: The interaction is documented and substantiated in peer-reviewed medical literature.
Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.
How To Manage The Interaction
Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.
It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.
Mechanism Of Interaction
The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.
Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.
Where Does Our Information Come From?
Information for our drug interactions is compiled from several drug compendia, including:
The prescribing information for each drug, as published on DailyMED, is also used.
Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.
The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.