Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). In a patient, theophylline has an elimination half-life of 8 h. Find the elimination rate constant k in h⁻¹.

Practice exercise (made-up values, not clinical guidance). A patient who weighs 89 kg needs a loading dose of vancomycin to reach a level of 20 mg/L straight away. The volume of distribution is 0.7 L/kg. Find the loading dose LD in mg.

Practice exercise (made-up values, not clinical guidance). An 87 kg patient is to be loaded with digoxin tablets to reach a level of 0.8 mcg/L. The volume of distribution is 7 L/kg and the tablets have a bioavailability F = 0.7. Find the total oral loading dose LD in mcg.

Practice exercise (made-up values, not clinical guidance). A 78 kg patient is to be loaded intravenously with phenytoin sodium to reach a phenytoin level of 20 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 71-year-old woman weighs 80 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 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). A vancomycin infusion runs at 80 mg/h with no loading dose. The patient's clearance is 4 L/h and the half-life is 10 h. What is the level C after 18 h?