Bioassay of metronidazole with either anaerobic or aerobic incubation.

In a bioassay for metronidazole, a modified agar well diffusion technique was used. Two clostridial species were used as the test organisms, and, with minor variations, the method was as effective with aerobic as with anaerobic incubation. Serum and urine levels of 0.25-128 mug/ml were measurable by this method without dilution of the specimens being assayed. The principal acid and alcohol metabolites of metronidazole were found to possess only approximately 5% and 30%, respectively, of the activity of the parent compound.