Pharmacokinetics of (+/-) -4-diethylamino-1,1-dimethylbut-2-yn-1-yl 2-cyclohexyl-2-hydroxy-2-phenylacetate monohydrochloride monohydrate. 2nd communication: tissue levels and enzyme activity in rats after repeated administration, and placental and milk transfer after single administration
Nakamura, A.; Hirota, T.; Sugihara, K.; Watanabe, S.; Tougou, K.; Morino, A.; Ezumi, Y.; Takaichi, M.
Arzneimittel-Forschung 47(2): 160-168
1997
ISSN/ISBN: 0004-4172 PMID: 9079235 Document Number: 477694
The absorption, distribution and excretion of radioactivity in rats were studied during and after repeated oral administration of 30 mg/kg of NS-21 ((+/-)-4-diethylamino-1, 1-dimethylbut-2-yn-1-yl 2-cyclohexyl-2-hydroxy-2-phenylacetate monohydrochloride monohydrate, CAS 129927-33-4) once a day for 21 days. The plasma concentrations of radioactivity 24 h after each administration of 14C-NS-21 reached a steady state on the 5th day. 48 h after the 21st administration, the plasma concentrations of radioactivity were under the detection limit. The plasma concentrations of the radioactivity after the 7th oral administration of 14C-NS-21 was higher than that after the single administration, but similar to those after the 14th and 21st administrations. There were no marked differences in the elimination half-lives after each administration. The urinary and fecal excretion of the radioactivity was 21.5 and 81.3%, respectively, within 168 h after the 21st administration. In most tissues, no radioactivity was observed 336 h after the 21st administration. Repeated oral administration of 30 and 100 mg/kg of NS-21 once a day for 7 days had no effect on the cytochrome P-450 content, aniline hydroxylase and aminopyrine N-demethylase activity in rat liver. The transfer of radioactivity into fetuses and milk was investigated after single oral administration of 14C-NS-21 to female rats. In the 18th day pregnant rats, the radioactivity concentrations were lower in most fetal tissues than in the maternal plasma. After oral administration of 14C-NS-21 to lactating rats, the concentrations of radioactivity were higher in the milk than in the maternal plasma during an 8-h period. No radioactivity was observed in milk 48 h after administration.