Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). A patient receives lidocaine as a constant IV infusion without a loading dose. The half-life is 2 h. What percentage f of the steady-state level has been reached after 2 h?

Practice exercise (made-up values, not clinical guidance). A patient who weighs 68 kg needs a loading dose of tobramycin to reach a level of 6 mg/L straight away. The volume of distribution is 0.3 L/kg. Find the loading dose LD in mg.

Practice exercise (made-up values, not clinical guidance). A 50 kg patient is to receive an aminophylline infusion (salt factor S = 0.8: 80% of aminophylline is theophylline). The theophylline clearance is 0.045 L/kg/h. What aminophylline infusion rate R in mg/h gives a steady-state theophylline level of 15 mg/L?

Practice exercise (made-up values, not clinical guidance). A patient receives an IV bolus of 240 mg of tobramycin. The level back-extrapolated to time zero is 10 mg/L and the half-life is 2 h. Find the volume of distribution Vd.

Practice exercise (made-up values, not clinical guidance). A 60-year-old woman weighs 59 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 for a creatinine clearance of 120 mL/min, and a fraction fe = 0.66 of the drug is excreted unchanged by the kidneys. Using the Dettli dose fraction Q = 1 − fe·(1 − CrCl/normal CrCl), find the adjusted dose D. Round to the nearest whole number.

Practice exercise (made-up values, not clinical guidance). A 54 kg patient takes oral aminophylline (S = 0.8, F = 1) every 12 h. The theophylline clearance is 0.04 L/kg/h. What dose D in mg gives an average steady-state level of 10 mg/L?