XELJANZ^® (tofacitinib) total daily dose should be reduced by half in patients receiving potent inhibitors of cytochrome P450 (CYP) 3A4 (e.g., ketoconazole) and in patients receiving 1 or more concomitant medicines that result in both moderate inhibition of CYP3A4 as well as potent inhibition of CYP2C19 (e.g., fluconazole) as follows:

• XELJANZ^® (tofacitinib) dose should be reduced to 5 mg once daily in patients receiving 5 mg twice daily.
• XELJANZ^® (tofacitinib) dose should be reduced to 5 mg twice daily in patients receiving 10 mg twice daily.

Since tofacitinib is metabolised by CYP3A4, interaction with medicines that inhibit or induce CYP3A4 is likely. Tofacitinib exposure is increased when co-administered with potent inhibitors of CYP3A4 (e.g., ketoconazole) or when administration of one or more concomitant medicines results in both moderate inhibition of CYP3A4 and potent inhibition of CYP2C19 (e.g., fluconazole).

Tofacitinib exposure is decreased when co-administered with potent CYP inducers (e.g., rifampicin).
Inhibitors of CYP2C19 alone or P-glycoprotein are unlikely to significantly alter the PK of XELJANZ^® (tofacitinib).

Co-administration with ketoconazole (strong CYP3A4 inhibitor), fluconazole (moderate CYP3A4 and potent CYP2C19 inhibitor), tacrolimus (mild CYP3A4 inhibitor) and ciclosporin (moderate CYP3A4 inhibitor) increased tofacitinib AUC, while rifampicin (potent CYP inducer) decreased tofacitinib AUC. Coadministration of tofacitinib with potent CYP inducers (e.g., rifampicin) may result in a loss of or reduced clinical response (see Figure 1). Co-administration of potent inducers of CYP3A4 with tofacitinib is not recommended. Co-administration with ketoconazole and fluconazole increased tofacitinib C_max while tacrolimus, ciclosporin and rifampicin decreased tofacitinib C_max.

Concomitant administration with MTX 15-25 mg once weekly had no effect on the PK of tofacitinib in RA patients (see Figure 1)

Co-administration of tofacitinib did not have an effect on the PK of oral contraceptives, levonorgestrel and ethinyl estradiol, in healthy female volunteers.

In RA patients, co-administration of tofacitinib with MTX 15 - 25 mg once weekly decreased the AUC and Cmax of MTX by 10% and 13%, respectively. The extent of decrease in MTX exposure does not warrant modifications to the individualised dosing of MTX.