Disposition of Q-35(1): Absorption and Excretion after Single Administration of 14C-Q-35 in Rats

The absorption and excretion of 14C labeled Q-35[(±)-1-Cyclopropyl-6-fluoro-1, 4-dihydro-8-methoxy-7-(3-methylaminopiperidin-1-yl)-4-oxoquinoline-3-carboxylic acid], a new fluoroquinolone antimicrobial agent, were studied in rats.1. When 14C-Q-35 was administered orally at the dose of 20 mg/kg to fasted rats, the radioactivity was absorbed rapidly and reached a maximum plasma concentration (Cmax) at 0.38 h, thereafter was eliminated at a half-life of 2.84 h.The AUC of the plasma radioactivity after an oral administration of 14C-Q-35 to nonfasted rats decreased to about half of AUC in fasted rats. It was suggested that there was a significant decrease in the extent of absorption by food.2. It was suggested that 14C-Q-35 was absorbed from the upper and middle segments of small intestine but scarcely from the stomach as revealed by the loop method of the digestive tracts.3. The urinary and fecal excretion rate of the radioactivity during 72 h after an oral administration of 14C-Q-35 to fasted rats were 42.2% and 56.5 % (total: 98.6%) of dose, respectively. It was suggested that the administered radioactivity was excreted in about 100% into the urine and feces.4. The biliary excretion rate during 24h after an oral administration of 14C-Q-35 to nonfasted rats was 32.3% of the dose, and the quarter of the radioactivity excreted to bile was reabsorbed.