PEBC MCQ Pharmaceutical Calculations question: age x weight kg x

PEBC MCQPharmaceutical Calculations

BR is a 72 year old male weighing 80 kg with a serum creatinine of 150 umol/L. Using CrCl (mL/min) = [(140 - age) x weight (kg) x 1.23] / SCr (umol/L), and multiplying by 0.85 for females, what is BR's estimated creatinine clearance?

a. 31 mL/min
b. 36 mL/min
c. 38 mL/min
d. 45 mL/min

Show the answer and explanation

Answer: d. 45 mL/min

CrCl = [(140 - 72) x 80 x 1.23] / 150 = (68 x 80 x 1.23) / 150 = 6,691 / 150 = 44.6, about 45 mL/min. The 0.85 factor applies only to females, so 38 mL/min is wrong for BR. Omitting the 1.23 SI conversion constant gives 36 mL/min, and making both errors (female factor and no constant) gives 31 mL/min. Source: Cockcroft DW, Gault MH. Nephron 1976;16:31 (SI form with constant 1.23 for males); KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD, ch. 1 and 4 (drug dosing).

Common mistake

Leaving out the SI unit constant when serum creatinine is in umol/L.

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