The Fate of Metronidazole and its Implications in Chemotherapy

1. [14C]Metronidazole was rapidly absorbed from the gastro-intestinal tract of rats giving maximum blood levels of radioactivity, equivalent to 6·4 and 6·7 μg metronidazole per ml blood, 1 h after oral dosing.2. There was rapid equilibration between blood and most tissues, although radioactivity was concentrated in the liver, kidney, gastro-intestinal tract and vaginal secretions.3. The half-life of clearance of radioactivity from the majority of tissues was between 3 and 4 h, although it was longer in the skin (8 h) and gastro-intestinal tract (14 h).4. Fourteen radioactive excretion products were detected in rat urine and all the major products were identified. These all contained a nitro group and represented 97% of the total radioactivity excreted in urine.5. Unchanged metronidazole was secreted throughout the entire length of the gastro-intestinal tract and into the vagina of rats.6. A hypothesis has been proposed to explain the high clinical efficacy of metronidazole in treating trichomonal and amoe...