Drug Interactions between Kisqali Femara Co-Pack and rivaroxaban

MONITOR: Coadministration with ribociclib may increase the plasma concentrations and pharmacologic effects of drugs that are substrates of CYP450 3A4. The proposed mechanism is decreased clearance due to ribociclib-mediated inhibition of CYP450 3A4 metabolism. In healthy study subjects, administration of midazolam, a sensitive CYP450 3A4 substrate, with multiple 400 mg daily doses of ribociclib increased the midazolam peak plasma concentration (Cmax) and systemic exposure (AUC) by 2.1-fold and 3.8-fold, respectively, compared to midazolam administered alone. When given at a clinically relevant dose of 600 mg daily, ribociclib is predicted to increase midazolam Cmax and AUC by 2.4-fold and 5.2-fold, respectively.

MANAGEMENT: Caution is advised when ribociclib is used concomitantly with drugs that undergo metabolism by CYP450 3A4, particularly those with a narrow therapeutic range. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever ribociclib is added to or withdrawn from therapy.

MONITOR: Coadministration with moderate or potent inhibitors of CYP450 3A4 may increase the plasma concentrations of rivaroxaban, which is a substrate of the isoenzyme. This interaction is not expected to be clinically significant in patients with normal renal function, but may be important in patients with renal impairment. When a single dose of rivaroxaban was coadministered with the moderate CYP450 3A4 inhibitor, fluconazole, rivaroxaban peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 30% and 40%, respectively. These increases are within the magnitude of the normal variability of Cmax and AUC and are not considered clinically relevant. However, the magnitude of interaction may be greater in patients with renal impairment. Even in the absence of concomitant CYP450 3A4 inhibitors, rivaroxaban AUC was increased 1.4-, 1.5- and 1.6 fold in individuals with mild (CrCl 50 to 80 mL/min), moderate (CrCl 30 to 49 mL/min) and severe (CrCl 15 to 29 mL/min) renal impairment, respectively, compared to healthy subjects with normal renal function (CrCl 80 mL/min or greater). Overall inhibition of factor Xa activity increased by a factor of 1.5, 1.9 and 2.0, and prolongation of PT was similarly increased by a factor of 1.3, 2.2 and 2.4, respectively. There are no data in patients with CrCl below 15 mL/min.

MANAGEMENT: In patients with significant renal impairment (e.g., CrCl between 15 to 50 mL/min), the use of rivaroxaban with moderate or potent inhibitors of CYP450 3A4 should be approached with caution. Patients should be routinely evaluated for signs and symptoms suggesting blood loss such as a drop in hemoglobin and/or hematocrit, hypotension, or fetal distress (in pregnant women). Renal function should also be assessed periodically, and treatment with rivaroxaban discontinued if acute renal failure develops. Due to the lack of clinical data, rivaroxaban is not recommended in patients with CrCl below 30 mL/min when used for the prophylaxis of deep vein thrombosis and in patients with CrCl below 15 mL/min when used for reducing the risk of stroke and systemic embolism in nonvalvular atrial fibrillation.