Drug Interactions between atazanavir and Torisel

GENERALLY AVOID: Coadministration of temsirolimus with potent inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of sirolimus, a major active metabolite of temsirolimus and known substrate of CYP450 3A4. According to the product labeling, administration of temsirolimus in combination with the CYP450 3A4 inhibitor ketoconazole resulted in a 2.2-fold and 3.1-fold increase in sirolimus peak plasma concentration (Cmax) and systemic exposure (AUC), respectively, compared to administration of temsirolimus alone. No significant effect on the pharmacokinetics of temsirolimus was reported.

MANAGEMENT: Concomitant use of temsirolimus with potent CYP450 3A4 inhibitors should generally be avoided. Some authorities recommend avoiding concomitant use of intravenous temsirolimus during and for 2 weeks after treatment with itraconazole (US). If coadministration is required, the manufacturer recommends reducing the temsirolimus dosage to 12.5 mg once a week. Based on pharmacokinetic studies, this dosage is predicted to adjust the sirolimus systemic exposure (AUC) to the range observed without inhibitors. However, clinical data are lacking. Following discontinuation of the potent CYP450 3A4 inhibitor, a washout period of approximately one week should be allowed before the temsirolimus dosage is adjusted upward to the normally recommended dosage (i.e., 25 mg once a week) or the dosage used prior to initiation of the CYP450 3A4 inhibitor.