Estradiol and norethindrone and Fosaprepitant interaction
Estradiol and norethindrone and Fosaprepitant: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Fosaprepitant (FOCINVEZ) label · effective 2026-03-30
Hormonal Contraceptives: Efficacy of contraceptives may be reduced during treatment and for 1 month following administration of the last dose of either fosaprepitant or oral aprepitant.
Risk of Reduced Efficacy of Hormonal Contraceptives Upon coadministration with fosaprepitant, the efficacy of hormonal contraceptives may be reduced during administration of and for 28 days following the last dose of fosaprepitant [see Clinical Pharmacology ( 12.3 )] .
Hormonal Contraceptives Clinical Impact Decreased hormonal exposure during administration of and for 28 days after administration of the last dose of fosaprepitant [see Warnings and Precautions ( 5.5 ), Use in Specific Populations ( 8.3 ), and Clinical Pharmacology ( 12.3 )] .
Examples birth control pills, transdermal systems, implants, and certain intrauterine systems CYP2C9 Substrates Warfarin Clinical Impact Decreased warfarin exposure and decreased prothrombin time (INR) [see Warnings and Precautions ( 5.4 ) and Clinical Pharmacology ( 12.3 )] .
From the Estradiol and norethindrone (Estradiol / Norethindrone Acetate) label · effective 2026-06-26
Inducers and/or inhibitors of CYP3A4 may affect estrogen drug metabolism and decrease or increase the estrogen plasma concentration.
Inhibitors of CYP3A4 such as erythromycin, clarithromycin, ketoconazole, itraconazole, ritonavir and grapefruit juice may increase plasma concentrations of estrogens and result in adverse reactions.
Therefore, inducers or inhibitors of CYP3A4 may affect estrogen drug metabolism.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
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.