Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). A patient receives vancomycin as a constant IV infusion without a loading dose. The half-life is 6 h. What percentage f of the steady-state level has been reached after 21 h?

Practice exercise (made-up values, not clinical guidance). The elimination rate constant of vancomycin in a patient is 0.116 h⁻¹. Find the half-life t½.

Practice exercise (made-up values, not clinical guidance). A patient has a lidocaine clearance of 550 mL/min. What infusion rate R in mg/min keeps the steady-state level at 2 mg/L?

Practice exercise (made-up values, not clinical guidance). A 62 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 68-year-old man weighs 95 kg and has a serum creatinine of 2.9 mg/dL (256 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 gentamicin half-life is 2 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.