Aprepitant - Warnings and Precautions

5 WARNINGS AND PRECAUTIONS • CYP3A4 Interactions : Aprepitant is a substrate, weak-to-moderate inhibitor and inducer of CYP3A4; See Full Prescribing Information for recommendations regarding contraindications, risk of adverse reactions, and dosage adjustments of aprepitant and concomitant drugs. ( 4 , 5.1 , 7.1 , 7.2 ) • Warfarin (a CYP2C9 substrate) : Risk of decreased INR of prothrombin time; monitor INR in 2-week period, particularly at 7 to 10 days, following initiation of aprepitant. ( 5.2 , 7.1 ) • Hormonal Contraceptives : Efficacy of contraceptives may be reduced during administration of and for 28 days following the last dose of aprepitant.

Use effective alternative or back-up methods of contraception. ( 5.3 , 7.1 , 8.3 ) 5.1 Clinically Significant CYP3A4 Aprepitant is a substrate, a weak-to-moderate (dose-dependent) inhibitor, and an inducer of CYP3A4.

Use of aprepitant with other drugs that are CYP3A4 substrates, may result in increased plasma concentration of the concomitant drug.

Use of pimozide with aprepitant is contraindicated due to the risk of significantly increased plasma concentrations of pimozide, potentially resulting in prolongation of the QT interval, a known adverse reaction of pimozide [see Contraindications ] .

Use of aprepitant with strong or moderate CYP3A4 inhibitors (e.g., ketoconazole, diltiazem) may increase plasma conentrations of aprepitant and result in an increased risk of adverse reactions related to aprepitant.

Use of aprepitant with strong CYP3A4 inducers (e.g., rifampin) may result in a reduction in aprepitant plasma concentrations and decreased efficacy of aprepitant.

See table 10 and 11 for a listing of potentially significant drug interactions [see Drug Interactions ( 7.1 , 7.2 )] .

5.2 Decrease in INR with Concomitant Warfarin Coadministration of aprepitant with warfarin, a CYP2C9 substrate, may result in a clinically significant decrease in International Normalized Ratio (INR) of prothrombin time [see Clinical Pharmacology ] .

Monitor the INR in patients on chronic warfarin therapy in the 2-week period, particularly at 7 to 10 days, following initiation of the 3-day regimen of aprepitant with each chemotherapy cycle, or following administration of a single 40-mg dose of aprepitant for the prevention of postoperative nausea and vomiting [see Drug Interactions ].

5.3 Risk of Reduced Efficacy of Hormonal Contraceptives Upon coadministration with aprepitant, the efficacy of hormonal contraceptives may be reduced during administration of and for 28 days following the last dose of aprepitant [see Clinical Pharmacology ].

Advise patients to use effective alternative or back-up methods of contraception during treatment with aprepitant and for 1 month following the last dose of aprepitant [see Drug Interactions , Use in Specific Populations ].