Absorption, plasma concentration, and excretion after single administration of 14C-(+-)-3-(benzylmethylamino)-2,2-dimethylpropyl methyl 4-(2-fluoro-5- nitrophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate hydrochloride in rats and dogs.

The absorption, plasma concentrations, and excretion of a newly synthesized calcium antagonist, TC-81 ((+-)-3-(benzylmethylamino)-2,2-dimethylpropyl methyl 4-(2-fluoro-5-nitrophenyl)-1,4-dihydro-2,6-dimethyl-3,5- pyridinedicarboxylate hydrochloride, CAS 96515-74-1) were studied following a single oral or intravenous administration of 14C-labelled compound. After oral administration, 14C-TC-81 was rapidly and well absorbed from the gastrointestinal tract. The peak plasma concentrations of radioactivity were observed at 0.5-1 h (rats) and 1-2 h (dogs) h after dosing. The elimination of the radioactivity in plasma was biphasic with a half-life of 3.8-5.2 h (a phase) and 42.9-56.2 h (beta phase) in the rats or 3.2 h (a phase) and 61.5 h (beta phase) in dogs. Maximum plasma concentrations of unchanged drug after oral administration of TC-81 to male rats at the doses of 0.5, 1.0, and 3.0 mg/kg were 1.7, 7.3 and 15.6 ng/ml, respectively. They were attained at 0.5 h after dosing in every dose examined. Plasma levels of unchanged drug declined with a half-life of 0.39-1.15 h. When TC-81 was orally administered to male dogs at the doses of 0.1, 0.2 and 0.5 mg/kg, plasma concentrations of unchanged drug reached the maximum level at 0.5 h after dosing and the values were 0.8, 3.3 and 9.6 ng/ml, respectively. They were eliminated with a half-life of 2.4-2.8 h. The absolute bioavailability of unchanged drug was estimated to be 2.6-7.0% (rats) and 5.3-15.5% (dogs) of the dose.(ABSTRACT TRUNCATED AT 250 WORDS)