Potential for drug interactions mediated by polymorphic flavin-containing monooxygenase 3 in human livers

Drug Metab Pharmacokinet. 2015 Feb;30(1):70-4. doi: 10.1016/j.dmpk.2014.09.008. Epub 2014 Oct 5.


Human flavin-containing monooxygenase 3 (FMO3) in the liver catalyzes a variety of oxygenations of nitrogen- and sulfur-containing medicines and xenobiotic substances. Because of growing interest in drug interactions mediated by polymorphic FMO3, benzydamine N-oxygenation by human FMO3 was investigated as a model reaction. Among the 41 compounds tested, trimethylamine, methimazole, itopride, and tozasertib (50 μM) suppressed benzydamine N-oxygenation at a substrate concentration of 50 μM by approximately 50% after co-incubation. Suppression of N-oxygenation of benzydamine, trimethylamine, itopride, and tozasertib and S-oxygenation of methimazole and sulindac sulfide after co-incubation with the other five of these six substrates was compared using FMO3 proteins recombinantly expressed in bacterial membranes. Apparent competitive inhibition by methimazole (0-50 μM) of sulindac sulfide S-oxygenation was observed with FMO3 proteins. Sulindac sulfide S-oxygenation activity of Arg205Cys variant FMO3 protein was likely to be suppressed more by methimazole than wild-type or Val257Met variant FMO3 protein was. These results suggest that genetic polymorphism in the human FMO3 gene may lead to changes of drug interactions for N- or S-oxygenations of xenobiotics and endogenous substances and that a probe battery system of benzydamine N-oxygenation and sulindac sulfide S-oxygenation activities is recommended to clarify the drug interactions mediated by FMO3.

Keywords: Drug interaction; Drug oxygenation; FMO3; FMO3 activity; FMO3 polymorphism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benzydamine / chemistry
  • Benzydamine / metabolism*
  • Catalysis
  • Drug Interactions
  • Humans
  • In Vitro Techniques
  • Microsomes, Liver / enzymology
  • Microsomes, Liver / metabolism*
  • Oxygenases / genetics*
  • Oxygenases / metabolism*
  • Pharmaceutical Preparations / chemistry
  • Pharmaceutical Preparations / metabolism*
  • Polymorphism, Genetic*
  • Recombinant Proteins
  • Substrate Specificity


  • Pharmaceutical Preparations
  • Recombinant Proteins
  • Benzydamine
  • Oxygenases
  • dimethylaniline monooxygenase (N-oxide forming)