Trough (ie, sample drawn immediately before a scheduled dose) Sirolimus concentrations are generally measured every 5 days. Blood drawn at other times will yield higher results
Most individuals display optimal response to sirolimus with trough whole blood levels 4.0 to 20.0 ng/mL. Preferred therapeutic ranges may vary by transplant type, protocol, and co-medications. Target concentrations vary depending on concomitant therapy, time post-transplant, the desired degree of immunosuppression, and adverse effects. When given with cyclosporine or tacrolimus, the therapeutic range for sirolimus is generally between 4 and 12 ng/mL, with minimal added benefit for concentrations >10 ng/mL. When sirolimus is given without calcineurin inhibitors, higher trough levels are needed; usually 12 to 20 ng/mL, but occasionally up to 20 to 30 ng/mL.
The assay is specific for sirolimus; it does not cross-react with tacrolimus, everolimus, cyclosporine, or any of their metabolites.