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OPRA Pharmacokinetics and Pharmacodynamics QUESTION #3839
Question 1
Small incremental dose increases of which drug may result in disproportionately large increases in plasma drug levels due to saturable (zero-order) kinetics?
  • Phenytoin✔️
  • Warfarin
  • Digoxin
  • Carbamazepine
Correct Answer Explanation
Phenytoin exhibits saturable Michaelis–Menten (non-linear) pharmacokinetics. Once hepatic enzymes are saturated, small dose increases cause disproportionate rises in plasma levels with potential toxicity.