Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). A patient who weighs 110 kg needs a loading dose of tobramycin to reach a level of 8 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). 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). After an IV dose of vancomycin, the level is 25 mg/L at 1 h and 12.5 mg/L at 13 h. Assume first-order elimination. 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 93 kg patient takes oral aminophylline (S = 0.8, F = 1) every 12 h. The theophylline clearance is 0.03 L/kg/h. What dose D in mg gives an average steady-state level of 15 mg/L?

Practice exercise (made-up values, not clinical guidance). A 42-year-old woman weighs 66 kg and has a serum creatinine of 3.4 mg/dL (301 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 gentamicin regimen is 80 mg every 8 h for a creatinine clearance of 120 mL/min. Keeping the dose, the interval is lengthened in proportion to the fall in clearance. Find the new dosing interval τ. Round to one decimal place.