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 9 h, and the drug is eliminated by first-order kinetics. What is the level C 15 h later?

Practice exercise (made-up values, not clinical guidance). A patient who weighs 102 kg needs a loading dose of gentamicin to reach a level of 10 mg/L straight away. The volume of distribution is 0.25 L/kg. Find the loading dose LD in mg.

Practice exercise (made-up values, not clinical guidance). A patient receives an IV bolus of 230 mg of gentamicin. The level back-extrapolated to time zero is 12 mg/L and the half-life is 2 h. Find the volume of distribution Vd.

Practice exercise (made-up values, not clinical guidance). After an IV dose of tobramycin, the level is 10 mg/L at 1 h and 2.5 mg/L at 5 h. Assume first-order elimination. Find the elimination rate constant k.

Practice exercise (made-up values, not clinical guidance). A 40-year-old man weighs 75 kg and has a serum creatinine of 1.4 mg/dL (124 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 ciprofloxacin dose is 500 mg for a creatinine clearance of 120 mL/min, and a fraction fe = 0.6 of the drug is excreted unchanged by the kidneys. Using the Dettli dose fraction Q = 1 − fe·(1 − CrCl/normal CrCl), find the adjusted dose D. Round to the nearest whole number.

Practice exercise (made-up values, not clinical guidance). A vancomycin infusion runs at 75 mg/h with no loading dose. The patient's clearance is 3 L/h and the half-life is 6 h. What is the level C after 11 h?