Distribution and metabolism of calcium [3H]metronidazolamate in mice

The blood radioactivity-time curve after iv calcium [3H]metronidazola-mate in mice was to be a diexponential model. It was rapidly distributed in various tissues. The highest radioactivities were found in liver and kidney, followed by lung, blood, heart, spleen, and the lowest in brain and testes. Bile and bone marrow contained only a slight radioactivity. In 7 d the cumulative excretion of radioactivity was 52 +/- 17% of the iv dose in urine and 10.3 +/- 2.4% in feces. The measurement by TLC and liquid scintillation counting of urine taken at 24 h after iv calcium [3H] metronidazolamate to mice revealed that approximately 77% of the total radioactivity in urine was excreted as the drug in unchanged form and 7% as its hydrolysate, metronidazole. Calcium [3H]metronidazolamate remained at a high level in blood on account of its longer T1/2 beta (34 h) and 20% were bound to plasma protein, thus making it available for longterm fractional radiotherapy of tumors.