Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). Just after an IV dose, the gentamicin level is 8 mg/L. The half-life is 3.5 h, and the drug is eliminated by first-order kinetics. What is the level C 13.5 h later?

Practice exercise (made-up values, not clinical guidance). A patient starts regular doses of phenobarbital, which has a half-life of 100 h. Using the rule that steady state is reached after about five half-lives, after how many hours t_ss is steady state reached?

Practice exercise (made-up values, not clinical guidance). After an IV dose of vancomycin, the level is 30 mg/L at 1 h and 16.8 mg/L at 11 h. Assume first-order elimination. Find the elimination rate constant k.

Practice exercise (made-up values, not clinical guidance). After an IV dose of gentamicin, the level is 7 mg/L at 1 h and 2.8 mg/L at 5 h. Assume first-order elimination. Find the elimination rate constant k.

Practice exercise (made-up values, not clinical guidance). An 83 kg patient takes oral theophylline (F = 1) every 12 h. The clearance is 0.045 L/kg/h. Each dose is 450 mg of theophylline. Find the average steady-state level C_ss,avg.

Practice exercise (made-up values, not clinical guidance). A 40-year-old man weighs 69 kg and has a serum creatinine of 2.1 mg/dL (186 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 digoxin dose is 250 mcg for a creatinine clearance of 120 mL/min, and a fraction fe = 0.7 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.