Renal Dosing & Adjustments Flashcards

A patient with a CrCl of 25 mL/min is prescribed vancomycin. Which pharmacokinetic parameter is most affected by renal impairment for this drug?

Answer: Elimination half-life

Vancomycin is renally eliminated, so its half-life is prolonged significantly as CrCl declines.

Which formula is most commonly used to estimate creatinine clearance in clinical practice for renal dosing adjustments?

Answer: Cockcroft-Gault equation

The Cockcroft-Gault equation is the standard for estimating CrCl used in drug dosing adjustments in most FDA labeling.

A 72-year-old woman weighing 50 kg with a serum creatinine of 1.0 mg/dL is prescribed a renally-cleared drug. Why might dosing based on her normal creatinine be misleading?

Answer: Low muscle mass can cause falsely normal creatinine despite reduced GFR

Elderly, low-muscle-mass patients may have reduced GFR despite normal serum creatinine because less creatinine is produced.

Which antibiotic requires the MOST significant dose reduction in a patient with CrCl of 10 mL/min?

Answer: Ciprofloxacin

Ciprofloxacin is substantially renally eliminated and requires significant dose reduction when CrCl falls below 30 mL/min.

When calculating CrCl using the Cockcroft-Gault equation for an obese patient (BMI 42), which weight should generally be used?

Answer: Adjusted body weight

Adjusted body weight (IBW + 0.4 × [TBW − IBW]) is recommended for obese patients to avoid overestimating CrCl.

A dialysis patient requires antibiotic therapy. Which agent can be used WITHOUT supplemental dosing after hemodialysis?

Answer: Vancomycin

Vancomycin is poorly dialyzed and generally does not require supplemental dosing after standard hemodialysis sessions.

Which drug is CONTRAINDICATED in patients with CrCl < 30 mL/min due to accumulation of a toxic metabolite?

Answer: Meperidine

Meperidine's metabolite normeperidine accumulates in renal impairment and can cause neurotoxicity and seizures.