Metronidazole (Flagyl): degradation by the intestinal flora.

1. Metronidazole (Flagyl) is reduced exponentially by the contents of the rat caecum in the absence of oxygen. The rate of removal is highest at pH 7 and 37 degrees. 2. Reduction of the drug is inhibited by boiling of the caecal contents, CHCl3, Cu2+, Ag+, azodicarboxylic acid bis-dimethylamide, p-chloromercuric benzoate, N-ethylmaleimide and 4,4,4-trifluoro-1,2-thienyl-1,3-butanedione. Nitrate, ethanol (3%), CO, phenol and amytal did not affect the rate of reduction. 3. It is concluded that iron-sulphur systems are involved in degradation of the drug.