Pharmacokinetics and metabolism of the cholecystokinin antagonist dexloxiglumide in male human subjects

Abstract

1. Mean concentrations of total 14 C and of dexloxiglumide at the end of single 20-min infusion doses of 14 C-dexloxiglumide (200 mg) to four healthy male subjects were 18.5 µ g eq. ml − 1 and 19.5 µ g ml − 1, respectively. The mean plasma clearance (0.22 l h − 1 kg − 1) and mean volume of distribution (V ss = 0.18 l kg − 1) were low. 2. Single oral doses of a solid formulation of 14 C-dexloxiglumide (200 mg) to the same subjects appeared to be rapidly and well absorbed. Mean peak plasma concentrations (C max) of total 14 C (2.8 µ g eq. ml − 1) and of dexloxiglumide (2.2 µ g ml − 1) occurred at about 1.5 h. Systemic availabilities of the oral dose based on total 14 C and dexloxiglumide were 70 and 48%, respectively. Thus, a proportion of an oral dose was subjected to presystemic elimination and the absorbed dose mainly eliminated by metabolism. Binding of dexloxiglumide to plasma proteins was extensive (96.6-99.2%). 3. Total 14 C was excreted mainly in the faeces. Mass balance of 14 C excretion was almost complete within 7 days when a mean of > 93% of the dose had been recovered. After the intravenous (i.v.) dose, mean totals of 23.7 and 69.8% of the dose were excreted in urine and faeces, respectively, during 7 days, and 19.5 and 73.7% of the dose, respectively, after the oral dose. The data were consistent with biliary excretion and perhaps some enterohepatic circulation of conjugates of dexloxiglumide and at least one of its metabolites. 4. LC-MS/MS of urine extracts showed that dexloxiglumide was metabolized by oxidation and conjugation. The former included at least two metabolites formed by monohydroxylation in the N- (3-methoxypropyl) pentyl side chain, and O-demethylation of this side chain followed by subsequent oxidation of the resultant alcohol to the dicarboxylic acid. At least one glucuronide was also present in urine. The main components in faeces appeared to be dexloxiglumide and a dicarboxylic metabolite formed by O-demethylation followed by oxidation of the N- (3-methoxypropyl) side chain. Both compounds were identified as their corresponding methyl esters formed because acid and methanol were used in the extraction procedure. Dexloxiglumide and the dicarboxylic acid were presumably excreted in bile as the glucuronic acid conjugates.