Rolapitant is a moderate CYP2D6 inhibitor. The inhibition of CYP2D6 persisted on Day 28 with a 2.3-fold increase in dextromethorphan concentrations, the last time point measured. The inhibitory effect of rolapitant on CYP2D6 is expected to persist beyond 28 days for an unknown duration following administration of VARUBI [see Clinical Pharmacology (12.3) ] . Oral rolapitant is an inhibitor of Breast-Cancer-Resistance Protein (BCRP) and p-glycoprotein (P-gp).
Rolapitant, given as a single oral dose, is not an inhibitor or inducer of CYP3A4 [see Clinical Pharmacology (12.3) ] . Therefore, no dosage adjustment for dexamethasone (CYP3A4 substrate) is needed when co-administered with VARUBI [see Dosage and Administration (2) ] . Table 4 and Table 5 include drugs with clinically important drug interactions when administered concomitantly with VARUBI and instructions for preventing or managing them.
Table 4: Clinically Relevant Interactions Affecting Drugs Co-Administered with VARUBI CYP2D6 Substrates Narrow Therapeutic Index Drugs (Thioridazine and Pimozide) Clinical Impact: Increased plasma concentrations of thioridazine and pimozide are associated with serious and/or life-threatening events of QT prolongation and Torsades de Pointes. Intervention: VARUBI is contraindicated in patients taking CYP2D6 substrates with a narrow therapeutic index such as thioridazine and pimozide.
If patients require these drugs, use an alternative antiemetic to VARUBI or an alternative to thioridazine or pimozide that is not metabolized by CYP2D6 [see Contraindications (4) , Warnings and Precautions (5.1) ]. Other CYP2D6 Substrates Clinical Impact: VARUBI can increase plasma concentrations of other CYP2D6 substrates for at least 28 days following administration of VARUBI and may result in adverse reactions. Before starting treatment with VARUBI consult the prescribing information of CYP2D6 substrates to obtain further information about interactions with CYP2D6 inhibitors [see Clinical Pharmacology (12.3) ].
Intervention: Before starting treatment with VARUBI consult the prescribing information of CYP2D6 substrates to obtain further information about interactions with CYP2D6 inhibitors [see Warnings and Precautions (5.1) ]. BCRP Substrates with a Narrow Therapeutic Index (e.g., methotrexate, topotecan, or irinotecan) Clinical Impact: Increased plasma concentrations of BCRP substrates (e.g., methotrexate, topotecan, or irinotecan) may result in potential adverse reactions [see Clinical Pharmacology (12.3) ].
Intervention: Monitor for adverse reactions related to the concomitant drug if use of VARUBI cannot be avoided. Use the lowest effective dose of rosuvastatin (see prescribing information for additional information on recommended dosing). P-gp Substrates with a Narrow Therapeutic Index (e.g. digoxin) Clinical Impact: Increased plasma concentrations of P-gp substrates (e.g., digoxin) may result in potential adverse reactions [see Clinical Pharmacology (12.3) ].
Intervention: Monitor digoxin concentrations with concomitant use of VARUBI and adjust the dosage as needed to maintain therapeutic concentrations. Monitor for adverse reactions if concomitant use of VARUBI with other P-gp substrates with a narrow therapeutic index cannot be avoided. Warfarin Clinical Impact: Although co-administration of intravenous rolapitant (VARBI is not approved for intravenous use), which has a higher C max than oral VARUBI, with warfarin did not substantially increase the systemic exposure to S-warfarin, the active enantiomer, the effects on INR and prothrombin time were not studied [see Clinical Pharmacology (12.3) ] .
Intervention: Monitor INR and prothrombin time and adjust the dosage of warfarin, as needed with concomitant use of VARUBI, to maintain the target INR range. Table 5: Clinically Relevant Interactions Affecting Rolapitant When Co-Administered with Other Drugs Strong CYP3A4 Inducers (e.g. rifampin) Clinical Impact: Co-administration of VARUBI with rifampin can significantly reduce the plasma concentrations of rolapitant and decrease the efficacy of VARUBI [see Clinical Pharmacology (12.3) ] .
Intervention: Avoid the use of VARUBI in patients who require chronic administration of strong CYP3A4 inducers. Strong CYP3A4 Inducers (e.g., rifampin) : significantly reduced plasma concentrations of rolapitant can decrease the efficacy of VARUBI; avoid use of VARUBI in patients who require chronic administration of such drugs. ( 7 ) BCRP and P-gp Substrates with a Narrow Therapeutic Index : Oral VARUBI is an inhibitor of BCRP and P-gp and can increase plasma concentrations of the concomitant drug and potential for adverse reactions.
See full prescribing information for specific examples. ( 7 ) Warfarin : Monitor for increased INR or prothrombin time; adjust the dose of warfarin as needed. ( 7 )
