Everolimus Drug Levels

Effective Thursday, August 18, 2011, the University of Iowa Hospitals and Clinics core clinical laboratory will begin running an assay to measure drug levels of everolimus (Zortress®, Afinitor®). This assay will be available in Epic as "EVEROLIMUS DRUG LEVEL" [LAB7456]. The test is an immunoassay from Thermo-Scientific (QMS® Everolimus) run on Roche Diagnostics analyzers.

Zortress® received FDA approval for prevention of organ rejection in adult kidney transplant recipients with a suggested therapeutic range of 3-8 ng/mL for a predose (trough) specimen. This is the reference range that is used in Epic for the everolimus assay.

Afinitor® received FDA approval for treatment of renal cell carcinoma and for the treatment of subependymal giant cell astrocytoma associated with tuberous sclerosis in patients who are not candidates for curative surgical resection. The suggested therapeutic range for this indication of everolimus is 5-10 ng/mL for a predose (trough) specimen.

The specimen type is lavender top (EDTA) tube - 3 mL whole blood from one lavender top tube (adults) or TWO EDTA microtainers (pediatric patients). The test will be available 7 days a week (including holidays) and routinely run one batch per day (similar to tacrolimus drug levels). The cutoff time for same day service is 9:00 AM for resulting by noon daily.

Sirolimus (rapamycin) cross-reacts significantly with the everolimus immunoassay. Everolimus blood concentrations cannot be determined reliably in patients whose blood has both sirolimus and everolimus. This can occur when patients are being transitioned from sirolimus to everolimus or everolimus to sirolimus. In transitioning patients from sirolimus to everolimus, the long therapeutic half-life of sirolimus (~2-3 days) should be kept in mind as it may take several weeks to completely eliminate sirolimus after drug discontinuation.

Questions should be directed to Matthew Krasowski, MD, PhD, medical director of the Clinical Chemistry Laboratory (384-9380, matthew-krasowski@uiowa.edu).