Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). A patient receives aminophylline as a constant IV infusion without a loading dose. The half-life is 8 h. What percentage f of the steady-state level has been reached after 20 h?

Practice exercise (made-up values, not clinical guidance). Just after an IV dose, the gentamicin level is 10 mg/L. The half-life is 2 h, and the drug is eliminated by first-order kinetics. What is the level C 7 h later?

Practice exercise (made-up values, not clinical guidance). After an IV dose of vancomycin, the level is 35 mg/L at 1 h and 19.6 mg/L at 11 h. Assume first-order elimination. Find the half-life t½.

Practice exercise (made-up values, not clinical guidance). A 79 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 61 kg patient takes oral theophylline (F = 1) every 8 h. The clearance is 0.05 L/kg/h. Each dose is 250 mg of theophylline. Find the average steady-state level C_ss,avg.

Practice exercise (made-up values, not clinical guidance). A 42-year-old woman weighs 80 kg and has a serum creatinine of 2.3 mg/dL (203 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 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.