Relative roles of CYP2C19 and CYP3A4/5 in midazolam 1'-hydroxylation

Xenobiotica. 2007 Jun;37(6):592-603. doi: 10.1080/00498250701358749.


1. During the characterization of recombinant CYP2C19, it was observed that this enzyme metabolized midazolam, which is generally regarded as CYP3A4/5 substrate, and we therefore decided to pursue this observation further. 2. CYP2C19 showed a Michaelis-Menten pattern for midazolam 1'-hydroxylation and was inhibited by (+)-N-3-benzylnirvanol and S-mephenytoin, which are a standard potent inhibitor and a substrate of CYP2C19, respectively. 3. The inhibitory potency by CYP3A4/5 inhibitor on the midazolam 1'-hydroxylation in human liver microsomes (HLM) was correlated with the CYP3A4/5 specific catalytic activity, but such correlation was not observed in CYP2C19 enzyme. The in vitro intrinsic clearance value for midazolam 1'-hydroxylation was not changed by the addition of (+)-N-3-benzylnirvanol in four individual HLM preparations. 4. These results indicated that although CYP2C19 is capable of catalyzing midazolam 1'-hydroxylation, CYP3A4/5 play a more important role.

MeSH terms

  • Aryl Hydrocarbon Hydroxylases / antagonists & inhibitors
  • Aryl Hydrocarbon Hydroxylases / physiology*
  • Cytochrome P-450 CYP2C19
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme Inhibitors
  • Cytochrome P-450 Enzyme System / physiology*
  • Enzyme Inhibitors / pharmacology
  • Humans
  • Hydroxylation / drug effects
  • Microsomes, Liver / metabolism
  • Midazolam / metabolism*
  • Mixed Function Oxygenases / antagonists & inhibitors
  • Mixed Function Oxygenases / physiology*
  • Recombinant Proteins / metabolism


  • Cytochrome P-450 Enzyme Inhibitors
  • Enzyme Inhibitors
  • Recombinant Proteins
  • Cytochrome P-450 Enzyme System
  • Mixed Function Oxygenases
  • Aryl Hydrocarbon Hydroxylases
  • CYP2C19 protein, human
  • CYP3A5 protein, human
  • Cytochrome P-450 CYP2C19
  • Cytochrome P-450 CYP3A
  • CYP3A4 protein, human
  • Midazolam