Drug Dosing in CRRT — FRCA Final MCQ

Instant feedback + full explanation. One question, done properly.

HardIntensive Care MedicineDrug Dosing in CRRTFRCA Final

An anuric, critically ill adult is receiving continuous venovenous haemodiafiltration through a high-flux membrane. Which antibiotic is best matched to the following dosing approach: administer an unreduced loading dose of 25–30 mg/kg, then individualise subsequent doses using measured serum concentrations because continuous renal replacement therapy materially increases its clearance despite poor removal by conventional intermittent haemodialysis?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Vancomycin

Vancomycin is correct. In critical illness, its 25–30 mg/kg loading dose should not be reduced for renal failure because the loading dose is determined mainly by volume of distribution. High-flux CRRT increases vancomycin clearance, so maintenance dosing must reflect the CRRT modality, residual renal function and therapeutic drug monitoring. Vancomycin protein binding is variable and moderate, approximately 30–55%, rather than “minimal.” Meropenem is the strongest distractor: it is only about 2% protein bound and is substantially removed by haemofiltration, so the original stem did not distinguish it from vancomycin. However, it does not match the stated vancomycin-specific loading and serum concentration-guided redosing strategy. Ceftriaxone and flucloxacillin are highly protein bound and poorly removed by dialysis. Teicoplanin is also highly protein bound and does not match this specified regimen.

Reference: electronic Medicines Compendium. Vancomycin 1000 mg powder for concentrate for solution for infusion, Summary of Product Characteristics, sections 4.2 and 5.2. Revised 19 January 2026. https://www.medicines.org.uk/emc/product/15737/smpc