1989 Volume 4 Issue 1 Pages 55-62
The absorption, metabolism and excretion of 14C-nizatidine were studied after a single oral administration of 5 mg/kg to male dogs.
1. The blood levels of radioactivity reached a peak level (1876 ng eq./ml) at 1 hr after administration and then declined with a half life of 2.05 hr until 12 hr.
2. Within 120 hr after administration, the excretion of radioactivity into urine and feces was 88.4 % and 8.1 % of the dose, respectively.
3. The in vitro plasma protein binding to dog plasma was 11.0-18.6% and that to human plasma was 23.9-45.4 % at concentrations range between 0.1 and 10 μg/mt. The plasma protein binding in dog plasma collected at 2, 4 and 8 hr after administration was 7.6, 5.8 and 15.7%, respectively.
4. In plasma and urine, unchanged drug, M-3 and S-oxide metabolites were mainly detected.
5. M-3 was identified nizatidine N-oxide by MS and NMR.
