Drug Interaction Report

MONITOR: Coadministration of temsirolimus with inhibitors of CYP450 3A4 may 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 potent 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: Caution is advised if temsirolimus is prescribed in combination with CYP450 3A4 inhibitors. Pharmacologic response to temsirolimus should be monitored more closely whenever a CYP450 3A4 inhibitor is added to or withdrawn from therapy, and the temsirolimus dosage adjusted as necessary. Patients should be advised to contact their physician if they experience increased adverse effects of temsirolimus such as hyperglycemia (e.g., excessive thirst; increased volume and/or frequency of urination), infections, fever, dyspnea, abdominal pain, diarrhea, and bloody stools.

GENERALLY AVOID: Coadministration of temsirolimus with grapefruit juice may increase the plasma concentrations of sirolimus, a major active metabolite of temsirolimus and known substrate of CYP450 3A4. The proposed mechanism is inhibition of CYP450 3A4-mediated metabolism by certain compounds present in grapefruits.

MANAGEMENT: Patients treated with temsirolimus should preferably avoid the consumption of grapefruit or grapefruit juice.