Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). Just after an IV dose, the vancomycin level is 30 mg/L. The half-life is 12 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 patient who weighs 70 kg needs a loading dose of gentamicin to reach a level of 8 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 90 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). An 88 kg patient is to be loaded intravenously with phenytoin sodium to reach a phenytoin level of 15 mg/L. The volume of distribution is 0.7 L/kg and the salt factor is S = 0.92. Find the loading dose LD of phenytoin sodium in mg.

Practice exercise (made-up values, not clinical guidance). A 63-year-old man weighs 92 kg and has a serum creatinine of 2.8 mg/dL (248 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 vancomycin regimen is 1000 mg every 12 h for a creatinine clearance of 120 mL/min. Keeping the dose, the interval is lengthened in proportion to the fall in clearance. Find the new dosing interval τ. Round to one decimal place.

Practice exercise (made-up values, not clinical guidance). An 89 kg patient takes oral theophylline (F = 1) every 8 h. The clearance is 0.04 L/kg/h. Each dose is 200 mg of theophylline. Find the average steady-state level C_ss,avg.