Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). A patient who weighs 105 kg needs a loading dose of theophylline to reach a level of 15 mg/L straight away. The volume of distribution is 0.5 L/kg. Find the loading dose LD in mg.

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 5 h later?

Practice exercise (made-up values, not clinical guidance). A patient receives an IV bolus of 160 mg of tobramycin. The level back-extrapolated to time zero is 7 mg/L and the half-life is 2 h. Find the clearance CL in L/h.

Practice exercise (made-up values, not clinical guidance). A patient receives an IV bolus of 100 mg of gentamicin. The level back-extrapolated to time zero is 7 mg/L and the half-life is 2.5 h. Find the volume of distribution Vd.

Practice exercise (made-up values, not clinical guidance). A patient's gentamicin half-life is 3 h. The target is a peak of 7 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 55-year-old man weighs 50 kg and has a serum creatinine of 1.8 mg/dL (159 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 levetiracetam dose is 1000 mg for a creatinine clearance of 120 mL/min, and a fraction fe = 0.66 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.