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 8 h?

Practice exercise (made-up values, not clinical guidance). The elimination rate constant of tobramycin in a patient is 0.347 h⁻¹. Find the half-life t½.

Practice exercise (made-up values, not clinical guidance). A 52 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 patient receives an IV bolus of 140 mg of tobramycin. The level back-extrapolated to time zero is 7 mg/L and the half-life is 3 h. Find the clearance CL in L/h.

Practice exercise (made-up values, not clinical guidance). A theophylline infusion is started without a loading dose. The half-life in this patient is 8 h. How long t does it take to reach 95% of the steady-state level?

Practice exercise (made-up values, not clinical guidance). A patient's gentamicin half-life is 3.5 h. The target is a peak of 7 mg/L and a trough of 1 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.