Tamoxifen (drug interactions)
Tamoxifen is a medication primarily used for the prevention and treatment of breast cancer by blocking the actions of estrogen and mimicking some estrogen-like effects. However, users of tamoxifen should be cautious about potential interactions with various substances. For instance, tangeretin, a bioflavonoid found in citrus fruits and supplements, may reduce tamoxifen's effectiveness, leading individuals to avoid high intakes of tangeretin or citrus fruits. The interaction between soy isoflavones is more complex; while low doses may hinder tamoxifen's cancer-fighting capabilities, higher doses could enhance its effectiveness. Additionally, other interactions include St. John’s wort, which can lower tamoxifen levels and its efficacy, and high doses of vitamin E, which may also interfere with the drug's action. Patients using blood thinners, chemotherapy, hormonal therapies, or CYP2D6 inhibitors are advised to consult their healthcare providers to manage potential adverse reactions effectively. Understanding these interactions is crucial for optimizing tamoxifen's therapeutic benefits while minimizing risks.
Subject Terms
Tamoxifen (drug interactions)
DEFINITION: A drug that blocks the actions of estrogen and produces some estrogen-like actions, used for the prevention and treatment of breast cancer.
INTERACTIONS: Soy isoflavones, tangeretin, St. John's wort, vitamin E, various prescription medications
TRADE NAME: Nolvadex
Tangeretin
Effect: Possible Harmful Interaction
Tangeretin is a bioflavonoid found in citrus fruit and some citrus bioflavonoid supplements. Animal studies suggest that a high intake of tangeretin reduces the effectiveness of tamoxifen. For this reason, people using tamoxifen should avoid supplements containing tangeretin and probably avoid excessive intake of citrus fruit.
Soy Isoflavones
Effect: Mixed Interaction
Like tamoxifen, soy isoflavones have estrogen-like and anti-estrogen actions. Test-tube and animal studies suggest that relatively low doses of soy isoflavones interfere with tamoxifen's ability to inhibit breast cancer growth, but high doses augment the effectiveness of tamoxifen.
Other Interactions
Several other interactions exist between tamoxifen and herbs, supplements, and prescription medications. Taking tamoxifen with St. John's wort may decrease tamoxifen levels in the body and, therefore, decrease the drug's effectiveness. Taking high doses of vitamin E may also interfere with the effectiveness of tamoxifen. Patients taking blood thinners, chemotherapy drugs, hormonal therapies, and CYP2D6 inhibitors should check with their healthcare provider due to the potential for adverse reactions.
Bibliography
Eldridge, Lynne. "Tamoxifen Drug Interactions - Cancer." Verywell Health, 5 July 2021, www.verywellhealth.com/tamoxifen-drug-interactions-4155225. Accessed 16 Sept. 2024.
Liu, B., et al. "Low-Dose Dietary Phytoestrogen Abrogates Tamoxifen-Associated Mammary Tumor Prevention." Cancer Research, vol. 65, 2005, pp. 879-886.
Perez, Alexandra. "Tamoxifen: Side Effects, Dosage, Uses, and More." Healthline, 22 June 2022, www.healthline.com/health/drugs/tamoxifen-oral-tablet. Accessed 16 Sept. 2024.
Yen, Christine, et al. "Interactions Between Natural Products and Tamoxifen in Breast Cancer: A Comprehensive Literature Review." Frontiers in Pharmacology, vol. 13, 2 June 2022, doi.org/10.3389%2Ffphar.2022.847113. Accessed 20 Dec. 2022.