Fosaprepitant and Rifampin interaction
Fosaprepitant and Rifampin: 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
Intervention Avoid concomitant use of FOCINVEZ Examples rifampin, carbamazepine, phenytoin
CYP3A4 Interactions: Fosaprepitant is a weak inhibitor of CYP3A4, and aprepitant, the active moiety, is a substrate, inhibitor, and inducer of CYP3A4; see Full Prescribing Information for recommendations regarding contraindications, risk of adverse reactions, and dosage adjustment of FOCINVEZ and concomitant drugs.
Use of FOCINVEZ with strong CYP3A4 inducers (e.g., rifampin) may result in a reduction in aprepitant plasma concentrations and decreased efficacy of FOCINVEZ.
Single dose fosaprepitant does not induce CYP3A4.
Co-administration of FOCINVEZ with drugs that are inhibitors or inducers of CYP3A4 may result in increased or decreased plasma concentrations of aprepitant, respectively, as shown in Table 8.
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.