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). Just after an IV dose, the vancomycin level is 35 mg/L. The half-life is 6 h, and the drug is eliminated by first-order kinetics. What is the level C 19 h later?

Practice exercise (made-up values, not clinical guidance). After an IV dose of gentamicin, the level is 10 mg/L at 2 h and 3.1 mg/L at 7 h. Assume first-order elimination. Find the half-life t½.

Practice exercise (made-up values, not clinical guidance). A 97 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 76-year-old woman weighs 62 kg and has a serum creatinine of 1.5 mg/dL (133 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 dose is 1000 mg every 12 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.

Practice exercise (made-up values, not clinical guidance). A patient's tobramycin half-life is 3.5 h. The target is a peak of 7 mg/L and a trough of 0.5 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.