- Renal: calculated creatinine clearance (CrCl) >= 45 mL/min based on the standard Cockcroft and Gault formula (see table below) or on measured glomerular filtration rate (GFR) using the appropriate radiolabeled method (51-CrEDTA or Tc99m-DTPA). Enrollment and dosing decisions based on creatinine clearance may be made using local lab values (calculated using the standard Cockcroft and Gault formula [see below]) The serum creatinine must be assayed at the same local lab each time for that patient.