Navigating the Shift From Cockcroft-Gault to eGFR for Drug Dosing

In this National Kidney Foundation (NKF) panel, Andrew Bzowyckyj, PharmD, BCPS, CDCES, senior scientific director and learning consultant at NKF, is joined by nephrology pharmacists:

• Rachel Khan, PharmD, associate professor of internal medicine and nephrology at the Virginia Commonwealth University School of Pharmacy;
• and Joanna Hudson, PharmD, BCPS, FASN, FCCP, professor in the departments of clinical pharmacy and translational science and medicine with an emphasis in nephrology at the University of Tennessee Health Sciences.

In this first episode, Hudson notes that estimated glomerular filtration rate (eGFR) is now the standard for assessing kidney filtration and is recommended by the Kidney Disease: Improving Global Outcomes guidelines for both staging and medication dosing. The preferred equation is the 2021 CKD-EPI equation, which no longer includes race. Khan adds that the Cockcroft-Gault equation, published in 1976, became embedded in drug labeling because it was the only tool available when the FDA issued its 1998 pharmacokinetic guidance.

The panelists explain that eGFR is standardized to a body surface area (BSA) of 1.73 m², which is useful for staging chronic kidney disease. For individualized dosing, however, renal drug clearance correlates most closely with mL/min. They recommend converting the lab-reported eGFR to a BSA-adjusted value by multiplying it by the patient’s BSA and dividing by 1.73, then comparing the result with Cockcroft-Gault. In patients with stable kidney function, the 2 often fall in the same range for dosing, and a discrepancy is a signal to check whether either equation is valid for that patient. Khan also advises pharmacists to confirm which equation their laboratory or electronic health record reports and notes that the NKF offers an online eGFR calculator that prioritizes the preferred equations.

Hudson points out that serum creatinine assays have been standardized since many package-insert dosing recommendations were developed, lowering average values by about 12%. As a result, today’s numbers are not directly comparable to those used in the original pharmacokinetic studies, and the FDA now encourages manufacturers to use contemporary eGFR equations. The panelists describe the current period as a transition rather than an outright replacement. Pharmacists should still understand Cockcroft-Gault, which remains on the NAPLEX and in some labeling, while weighing multiple equations and the clinical context to make sound dosing decisions.

Learn more about the National Kidney Foundation at kidney.org and at this link.