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Renal Function
Creatinine Clearance (Cockcroft-Gault)
Estimate creatinine clearance for drug dosing and CKD staging using Cockcroft-Gault.
When to use: Use Cockcroft-Gault to estimate creatinine clearance for drug dose adjustment — it remains the regulatory standard used in clinical pharmacology trials. Apply before prescribing renally cleared medications (aminoglycosides, metformin, direct oral anticoagulants, digoxin, LMWH). Use IBW in obese patients and actual body weight otherwise. Note that it overestimates in muscular patients and underestimates in the elderly with low muscle mass.
Calculator
Use actual body weight; use IBW if obese
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Formula
CrCl = [(140 − age) × weight (kg)] / [72 × Scr (mg/dL)] × 0.85 (if female)
≥60: Normal | 45–59: Mild reduction | 30–44: Moderate | 15–29: Severe | <15: Kidney failure
Key Points for NEET PG
- Formula: CrCl = [(140 − age) × weight] / (72 × Scr) × 0.85 if female — the most commonly tested renal formula in NEET PG pharmacology.
- Metformin is contraindicated when CrCl <30 mL/min (risk of lactic acidosis) — a classic pharmacology MCQ.
- Dose reduction mandatory at CrCl <50: vancomycin, aminoglycosides, digoxin, DOACs (rivaroxaban, apixaban, dabigatran).
- Cockcroft-Gault measures CrCl (mL/min); CKD-EPI and MDRD estimate GFR (mL/min/1.73 m²) — CrCl ≈ GFR but is NOT identical.
- In acute kidney injury (AKI), Cockcroft-Gault is unreliable because creatinine is not at steady state — use clinical judgment and serial measurements.
References
Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine · Nephron (1976)
Inker LA et al. Estimating glomerular filtration rate from serum creatinine and cystatin C · N Engl J Med (2012)
For educational purposes only. Not for clinical decision-making without professional oversight.