The standard Cockcroft and Gault formula (based on actual weight) or the measured glomerular filtration rate (GFR) using the appropriate radiolabeled method (51-CrEDTA or Tc99m-DTPA) must be used to calculate CrCl for enrollment or dosing. The same method used at baseline should be used throughout the study. Insufficient numbers of patients have been studied with creatinine clearance <45 mL/min to give a dose recommendation. Therefore, pemetrexed should not be administered to patients whose creatinine clearance is <45 mL/min.