Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). Just after an IV dose, the vancomycin level is 35 mg/L. The half-life is 7 h, and the drug is eliminated by first-order kinetics. What is the level C 28 h later?

Practice exercise (made-up values, not clinical guidance). Just after an IV dose, the vancomycin level is 25 mg/L. The half-life is 10 h, and the drug is eliminated by first-order kinetics. What is the level C 12 h later?

Practice exercise (made-up values, not clinical guidance). A 98 kg patient is to receive an aminophylline infusion (salt factor S = 0.8: 80% of aminophylline is theophylline). The theophylline clearance is 0.04 L/kg/h. What aminophylline infusion rate R in mg/h gives a steady-state theophylline level of 12 mg/L?

Practice exercise (made-up values, not clinical guidance). A patient receives an IV bolus of 140 mg of gentamicin. The level back-extrapolated to time zero is 6 mg/L and the half-life is 3.5 h. Find the clearance CL in L/h.

Practice exercise (made-up values, not clinical guidance). A patient's tobramycin half-life is 4 h. The target is a peak of 6 mg/L and a trough of 1 mg/L. Assuming rapid IV doses and first-order elimination, what dosing interval τ lets the level fall from the peak to the trough? Round to one decimal place.

Practice exercise (made-up values, not clinical guidance). A 44-year-old woman weighs 64 kg and has a serum creatinine of 2.2 mg/dL (194 µmol/L). Estimate the creatinine clearance with Cockcroft–Gault: CrCl (mL/min) = (140 − age) × weight (kg)/(72 × SCr in mg/dL), × 0.85 for women. The usual cefazolin dose is 1000 mg every 8 h for a creatinine clearance of 100 mL/min. Keeping the interval, the dose is reduced in proportion to the creatinine clearance. Find the adjusted dose D. Round to the nearest whole number.