Trying to understand first order and zero order kinetics

{My own study points.}

First Order Kinetics

  • Higher plasma concentrations means higher metabolization rate.
  • Metabolism is directly proportional with drug concentrations.
  • Drug is eliminated from the body related to the plasma levels.
  • Constant half-life. (Metabolize 50% of drug)

Zero Order Kinetics

  • Higher plasma concentrations doesn't mean higher metabolization rate.
  • Metabolism is independent from plasma concentrations.
  • Drug concentration in the body increase with time disregarding the elimination rate leading to toxic side effects.
  • Constant rate of drug metabolism.


First order is Good, Zero order is BAD.

First order is occurring with most medications.

First order: constant proportion of the drug is eliminated per unit time.
Zero order: constant amount of the drug is eliminated per unit time.


Pharmacist interested in improving the health outcome for every single case he meets.

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