Estradiol and Fulvestrant interaction
Estradiol and Fulvestrant: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Estradiol (Delestrogen) label · effective 2026-05-13
CARDIOVASCULAR AND OTHER RISKS Estrogens and progestins should not be used for the prevention of cardiovascular disease [see WARNINGS , Cardiovascular disorders ].
Other doses of oral conjugated estrogens with medroxyprogesterone acetate, and other combinations and dosage forms of estrogens and progestins were not studied in the WHI clinical trials and, in the absence of comparable data, these risks should be assumed to be similar.
Exacerbation of other conditions Estrogens may cause an exacerbation of asthma, diabetes mellitus, epilepsy, migraine or porphyria, systemic lupus erythematosus, and hepatic hemangiomas and should be used with caution in women with these conditions.
From the Fulvestrant (CLIGAVYX) label · effective 2026-06-24
Interference of Fulvestrant with Serum Estradiol Immunoassays Due to structural similarity of fulvestrant and estradiol, fulvestrant can interfere with estradiol measurement by immunoassay, resulting in falsely elevated estradiol levels [see Warnings and Precautions (5.4) ] .
Immunoassay Measurement of Serum Estradiol: CLIGAVYX can interfere with estradiol measurement by immunoassay, resulting in falsely elevated estradiol levels.
Immunoassay Measurement of Serum Estradiol Due to structural similarity of fulvestrant and estradiol, fulvestrant can interfere with estradiol measurement by immunoassay, resulting in falsely elevated estradiol levels.
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.