Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug are: anastrozole, "blood thinners" (such as warfarin), estrogens, letrozole, hormonal forms of birth control (such as birth control pills, patches, implants), ribociclib.

Other medications can affect the removal of tamoxifen from your body, which may affect how tamoxifen works. Examples include butalbital, cimetidine, mitotane, rifamycins (such as rifampin), secobarbital, SSRI antidepressants (such as fluoxetine, paroxetine), St. John's wort, drugs used to treat seizures (such as carbamazepine, phenobarbital, phenytoin, primidone), among others.

This medication may interfere with certain lab tests (such as thyroid tests), possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.