Glomerular filtration Rate, Cockcroft

Used for drug dosing decisions when a weight‑based creatinine clearance estimate is required, especially for renally cleared drugs and in oncology where many pharmacokinetic studies historically used this method 1 [Level I evidence]. Clinically useful to approximate CrCl when measured GFR is unavailable, though accuracy decreases in extremes of body size or critical illness; measured GFR is advised when dosing has a narrow therapeutic index or serious toxicity risk 2 [Level I evidence].

Adjust for major limitations: relies on serum creatinine, assumes stable kidney function, and is strongly distorted by extremes of body weight, edema, obesity, sarcopenia, cachexia, and assay variability (KDIGO 2024 1).
Use creatinine–cystatin C eGFR or measured GFR when accuracy affects drug dosing—especially narrow‑therapeutic‑index agents or oncology regimens, where Cockcroft‑Gault can misestimate clearance (KDIGO 2024 1).