Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). The elimination rate constant of digoxin in a patient is 0.0144 h⁻¹. Find the half-life t½.

Practice exercise (made-up values, not clinical guidance). A patient starts regular doses of phenobarbital, which has a half-life of 96 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 gentamicin, the level is 8 mg/L at 1 h and 3.2 mg/L at 5 h. Assume first-order elimination. Find the half-life t½.

Practice exercise (made-up values, not clinical guidance). A patient receives an IV bolus of 180 mg of tobramycin. The level back-extrapolated to time zero is 7 mg/L and the half-life is 3 h. Find the volume of distribution Vd.

Practice exercise (made-up values, not clinical guidance). A 70 kg patient takes oral theophylline (F = 1) every 12 h. The clearance is 0.035 L/kg/h. Each dose is 500 mg of theophylline. Find the average steady-state level C_ss,avg.

Practice exercise (made-up values, not clinical guidance). A 41-year-old woman weighs 61 kg and has a serum creatinine of 2 mg/dL (177 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 vancomycin 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.