Pharmacokinetics and bioavailability of a newly synthesized dihydropyridine compound with multidrug resistance reversal activity

(+/-)3-(3-(4,4-diphenylpiperidin-1-yl)propyl) 5-methyl 4-(3,4-dimethoxyphenyl)-2,6-dimethyl -1,4-dihydropyridine-3,5-dicarboxylate ((±)-DHP-014), is a new 4-aryl-1,4-dihydropyridine that can reverse multidrug resistance mediated by the ATP-binding cassette (ABC) transport proteins, P-glycoprotein, multidrug resistance-associated protein 1 and breast cancer resistance protein; it exhibits negligible calcium channel blocking activity. The objective of this work was to investigate the pharmacokinetics of this new compound in rats. Three intravenous (1, 2 and 5 mg/kg) and two oral (25 and 50mg/kg) doses were administered to female Sprague-Dawley rats. A two-compartment model with nonlinear elimination best characterized the pharmacokinetic profiles after intravenous and oral administration in rats. The terminal half-life of (±)-DHP-014 increased and the systemic clearance significantly decreased at higher doses, indicating nonlinear elimination. The dose-dependent clearance is likely due to saturation of metabolism. The apparent volume of distribution of (±)-DHP-014 was 2.0 L/kg in rats and was unchanged with increasing intravenous doses of (±)-DHP-014. The estimated oral bioavailability of (±)-DHP-014 was 8.2%. The poor bioavailability is likely due to the poor solubility of the compound, as well as to substantial first-pass elimination.