The disposition of [14C]metronidazole in rats following vaginal and oral administration

The absorption, tissue distribution and excretion of [17C]metronidazole (14C-MTZ) were compared during the first 4 h after administration of 10 mg kg-1 of 14C-MTZ either orally or intravaginally (i.v.g.) to rats. Peak 14C blood concentrations were reached at 1 h in both groups. Blood samples collected at 0.5, 3 and 4 h had a higher 14C concentration in orally dosed rats (P less than 0.05) than in i.v.g.-treated animals. About 3% of the i.v.g. applied dose remained in the vagina at 4 h. After 4 h, the plasma, liver, kidney, brain, lung and uterus concentrations of 14C were similar in both groups, whereas the blood, skeletal muscle and fat 14C values were significantly greater in the orally dosed rats. The total recoveries of 14C in the urine and faeces did not differ (ca 38% over 4 h) between the two groups. These results suggest that the kinetics of metronidazole are similar after the administration of equal amounts of this drug by either route.