Inhibition of diamine oxidase activity by metronidazole.

Metronidazole was found to be a non-competitive inhibitor of man, rabbit and rat intestinal diamine oxidases with an inhibition constant value of approximately 10(-4) M. The purified bovine serum amine oxidase was not inhibited, whereas the purified swine kidney enzyme gave similar results. These findings suggest that metronidazole and similar compounds, used as antibacterial and antiprotozoal drugs, should be given under careful control, especially when administered for long times, because a decrease of intestinal diamine oxidase activity was proven to be a risk factor for several pathologies of this organ.