Creatinine Clearance (Cockcroft-Gault) Practice
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Creatinine clearance estimates kidney function to guide renal dose adjustments. The Cockcroft-Gault equation is the pharmacy standard. The trickiest part is choosing the right body weight before plugging in.
FormulasCrCl = [(140 − age) × weight] ÷ (72 × SCr) × 0.85 if femaleIBW first → actual < IBW use actual; actual > 125% of IBW use AdjBW = IBW + 0.4(actual − IBW); otherwise IBW
Worked example
70-yr-old male, 5'10" (IBW = 73 kg), weighs 90 kg, SCr 1.2. Since 90 < 125% of 73, use IBW. CrCl = (140 − 70) × 73 ÷ (72 × 1.2) = 59.1 mL/min.
💡 Weight rule first, formula second — using actual weight when AdjBW is required is the classic error.