Enzyme Inhibition Interactions

• Effect varies according to dose (amount), potency (strength)

• Quick onset, resolution of interaction

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• Inhibition interactions occur when two agents compete for the same enzymatic binding site

• Competitive inhibition depends upon:
  • the affinity of the substrate for the enzyme being inhibited
  • the concentration of substrate required for inhibition
  • the half-life of the inhibitor drug

• These types of interactions usually occur rapidly, i.e., within a few doses, once sufficient concentrations of the inhibiting agent are present in the liver.

• These interactions also tend to resolve quickly once the offending agent (inhibitor) is removed

• Another, less common mechanism of inhibition is noncompetitive; this can occur as a result of inactivation of the enzyme. The duration of this type of inhibition may be longer if new enzymes need to be synthesized after removal of the inhibitor drug.