A patient was given a 160-mg dose of drug by intravenous (IV), and 20 mg was eliminated during the first 120 minutes. If the drug follows zero order elimination kinetics, how much of the drug will remain 10 hours after administration?

A patient was given a 160-mg dose of drug by intravenous (IV), and 20 mg was eliminated during the first 120 minutes. If the drug follows zero order elimination kinetics, how much of the drug will remain 10 hours after administration?

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Answer

• Amount of drug remaining after 10 hours after administration = 60 mg
  Explanation:
  For Zero-order kinetics, the same amount of drug is eliminated irrespective of drug concentration at any time
  This means that the amount of drug eliminated the first minute is equal to the same amount of drug eliminated in the last minute.
  Amount of drug = 160 mg
  Amount eliminated first 120 minutes = 20 mg
  Amount eliminated every one hour = 10 mg = (20 / 2 hrs)
  This implies that after every one hour, 10 mg of the drug will be eliminated until the last drug concentration
  After 10 hours, amount of drug eliminated will be
  10 hrs * 10 mg = 100 mg
  Amount remaining
  160 mg – 100 mg = 60 mg