Clinical pharmacokinetics worksheet with answers

Practice exercise (made-up values, not clinical guidance). A patient starts regular doses of vancomycin, which has a half-life of 8 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). A patient receives vancomycin as a constant IV infusion without a loading dose. The half-life is 10 h. What percentage f of the steady-state level has been reached after 30 h?

Practice exercise (made-up values, not clinical guidance). After an IV dose of vancomycin, the level is 40 mg/L at 2 h and 10 mg/L at 14 h. Assume first-order elimination. Find the half-life t½.

Practice exercise (made-up values, not clinical guidance). After an IV dose of gentamicin, the level is 10 mg/L at 1 h and 5 mg/L at 4 h. Assume first-order elimination. Find the elimination rate constant k.

Practice exercise (made-up values, not clinical guidance). A 51-year-old woman weighs 68 kg and has a serum creatinine of 1.5 mg/dL (133 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 100 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.

Practice exercise (made-up values, not clinical guidance). A 74 kg patient takes oral aminophylline (S = 0.8, F = 1) every 8 h. The theophylline clearance is 0.04 L/kg/h. What dose D in mg gives an average steady-state level of 15 mg/L?