Aprepitant and Fosaprepitant interaction
Aprepitant and Fosaprepitant: the Fosaprepitant prescribing label flags 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 Fosaprepitant (FOCINVEZ) label · effective 2026-03-30
Inhibition of CYP3A4 by aprepitant, the active moiety, could result in elevated plasma concentrations of this drug, which is a CYP3A4 substrate, potentially causing serious or life-threatening reactions, such as QT prolongation, a known adverse reaction of pimozide [see Warnings and Precautions ( 5.1 )] .
Table 7 Effects of Fosaprepitant/Aprepitant on the Pharmacokinetics of Other Drugs CYP3A4 Substrates Pimozide Clinical Impact Increased pimozide exposure Intervention FOCINVEZ is contraindicated [see Contraindications ( 4 )] .
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.
Use of FOCINVEZ with strong or moderate CYP3A4 inhibitors (e.g., ketoconazole, diltiazem) may increase plasma concentrations of aprepitant and result in an increased risk of adverse reactions related to FOCINVEZ.
Advise patients to use effective alternative or back-up methods of contraception during treatment with FOCINVEZ and for 1 month following administration of the last dose of fosaprepitant or oral aprepitant [see Drug Interactions ( 7.1 ), and Use in Specific Populations ( 8.3 )] .
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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.