Metabolism of clentiazem in rats

Following oral dosing of [14C]clentiazem to rats the metabolites in urine and bile were separated and their chemical structures were investigated by HPLC and GC-MS analyses. Fifteen basic, 6 acidic, 2 neutral and 4 conjugated metabolites were found in urine and/or bile. Eight basic metabolites (MB1-8) were identified as the synthetic compounds; deacetyl clentiazem (MB1), N-monodemethyl clentiazem (MB2), deacetyl-N-monodemethyl clentiazem (MB3), deacetyl-O-demethyl clentiazem (MB4), N-monodemethyl-O-demethyl clentiazem (MB5), deacetyl-N-monodemethyl-O-demethyl clentiazem (MB6), O-demethyl clentiazem (MB7) and N-didemethyl clentiazem (MB8). The chemical structures of seven basic metabolites (MB9-15) were assigned as follows, deacetyl-N-didemethyl clentiazem (MB9), O-demethyl-N-didemethyl clentiazem (MB10), deacetyl-O-demethyl-N-didemethyl clentiazem (MB11), N-monodemethyl-2-hydroxy-methoxyphenyl clentiazem (MB12), deacetyl-2-hydroxy-methoxyphenyl clentiazem (MB13), deacetyl-N-monodemethyl-2-hydroxy-methoxyphenyl clentiazem (MB14) and deacetyl-N-didemethyl-2-hydroxy-methoxyphenyl clentiazem (MB15). Four acidic metabolites were identified as the synthetic compounds: (+)-(2S,3S)-3-(acetyloxy)-8-chloro-3,4-dihydro-2-(4-methoxyphenyl) -4-oxo-1, 5-benzothiazepin-5(2H)-acetic acid (MA1), deacetyl-MA1 (MA2), O-demethyl-MA1 (MA3) and deacetyl-O-demethyl-MA1 (MA4); and the two remaining acidic metabolites, MA5 and MA6, were presumed to be hydroxylated MA3 and MA4, respectively. Two neutral metabolites were identified as the synthetic compounds; (+)-(2S,3S)-3-(acetyloxy)-8-chloro-3,4-dihydro-2-(4-methoxyphenyl) -4-oxo-1, 5-benzothiazepin-5(2H)-acetonitrile (MN1) and deacetyl MN1 (MN2). Other two metabolites conjugated with glucuronic acid were found in bile and the structures were presumed to be 8-chloro-2,3-dihydro-3-hydroxy-5-(2-hydroxyethyl)-2-(4-hydroxyphenyl)-1, 5-benzothiazepin-4(5H)-one (MN3) and 2-methoxyphenyl MN3 (MN4). The glucuronide or sulfate of MA4 was also detected. These metabolites were formed by a number of pathways including deacetylation, deamination, N-demethylation, O-demethylation, aromatic hydroxylation and conjugation.