Pharmacokinetic Studies of Betotastine Besilate (TAU-284). (II): Distribution and Excretion after Repeated Oral Administration, and Transfer into the Fetus and Milk of Rats.

Abstract

The distribution and excretion of radioactivity was studied following a 21-day period of daily oral administration of 14C-TAU-284 to male rats. Furthermore, the transfer of radioactivity into the fetus and milk was also studied on the 12th and 18th day of pregnancy in rats, and in lactating female rats. 1. When measured at 24 hrs after each of 21 repeated dosings to male rats with 14-C-TAU-284, the levels of radioactivity in the blood reached the steady-state by the 16th dosing. The decrease of radioactivity in blood after repeated dosings for 21 days was slower than that after a single dosing. 2. In the distribution of radioactivity after the 21st dosing, the radioactivity in the liver and kidney was higher than that in other tissues. The radioactivity in cerebrum, eye balls, fat, seminal vesicles and testis were low. And radioactivity levels in other tissues were moderate. The tissue levels of radioactivity increased after each dosing during repeated administration. 3. Transfer to blood cells also increased by repeated dosing. Most radioactivity in blood cell was associated with a globin fraction. 4. The total ex cretion of radioactivity in urine and feces during each 24 hrs after daily dosing was almost constant. 5. The levels of radioactivity in the fetal liver 30 minutes after oral administration to 18th day in pregnant rats were about the same as in maternal plasma. The levels of radioactivity in other fetal tissues were 1/3 to 1/10 of that in maternal plasma. 6. The radioactivity level in the milk reached a maximum (0.40 μg eq./ml) at 1 hr after oral administration to 11 day-lactating rats. The radioactivity in milk 48 hrs after dosing was bellow the detection limit. The radioactivity in milk at each measured time was higher than that in plasma of lactating rat.