Abstract
The absorption and excretion of radioactivity after a single oral administration of [14C] grepafloxacin (GPFX) at 20 mg/kg were investigated in monkeys and dogs.
1. The mean plasma concentration of radioactivity reached a maximum of 3.29μg eq./g at 2 hours in monkeys, and declined thereafter with a biological half-life of 5.9 hours. The AUC during the period of 0-48 hours was 39.6μg eq. h/g. The blood concentration was higher than 0.8-1.3 times the plasma concentration.
2. The mean plasma concentration of radioactivity reached a maximum of 4.80μg eq./ml at 2 hours in dogs, and declined thereafter with a biological half-life of 3.8 hours. The AUC during the period of 0-24 hours was 38.3μg eq. h/ml. The blood concentration was higher than 0.9-1.2 times the plasma concentration.
3. The in vitro binding rates of [14C] GPFX to monkey and dog plasma were 41%-48%, with no concentration-dependency. The in vivo binding rates of GPFX to monkey and dog plasma were 45.7% 47.5%, similar to the in vitro rates.
4. The urinary and fecal excretion rates of radioactivity during the period of 0-120 hours in monkeys were 13.1% and 54.1%, respectively, of the administered dose.
5. In dogs, the urinary and fecal excretion rates of radioactivity during the period of 0-168 hours were 16.0% and 80.3%, respectively, of the administered dose.
