Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). Just after an IV dose, the gentamicin level is 9 mg/L. The half-life is 3 h, and the drug is eliminated by first-order kinetics. What is the level C 12 h later?

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 1.5 h. What percentage f of the steady-state level has been reached after 5.25 h?

Practice exercise (made-up values, not clinical guidance). After an IV dose of tobramycin, the level is 6 mg/L at 2 h and 0.8 mg/L at 8 h. Assume first-order elimination. Find the half-life t½.

Practice exercise (made-up values, not clinical guidance). A 68 kg patient is to be loaded with digoxin tablets to reach a level of 0.8 mcg/L. The volume of distribution is 7 L/kg and the tablets have a bioavailability F = 0.7. Find the total oral loading dose LD in mcg.

Practice exercise (made-up values, not clinical guidance). A 46-year-old woman weighs 92 kg and has a serum creatinine of 1.2 mg/dL (106 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 120 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 vancomycin infusion runs at 100 mg/h with no loading dose. The patient's clearance is 4 L/h and the half-life is 6 h. What is the level C after 13 h?