Evaluation of clopidogrel conjugation metabolism: PK studies in man and mice of clopidogrel acyl glucuronide

Abstract

The existence of a glucuronide conjugate of the major circulating clopidogrel metabolites, called clopidogrel acyl glucuronide (CAG), is already known. However, information regarding its pharmacokinetics (PK), metabolism, and clearance are modest. We investigated in vivo the potential CAG trans-esterification to clopidogrel (reaction occurring in vitro in particular conditions) by administering the metabolite to mice. Experiments were then carried out on men, clopidogrel administered alone or followed by activated charcoal intake (intestinal reabsorption blockade). Study objectives included: PK comparison of CAG, clopidogrel carboxylic acid (CCA), and clopidogrel in plasma, determination of their elimination patterns in urine and feces, and tracking of charcoal-induced changes in PK and/or urinary excretion that would indicate relevant enterohepatic recycling of CAG. In mice, CAGwas rapidly hydrolyzed toCCAafter oral administration,whereas by intravenous route metabolic conversion to CCA was delayed. No levels of clopidogrel were detected in mice plasma, excluding any potential trans-esterification or other formof back-conversion in vivo. PK experiments in man showed that CAG is hydrolyzed in the gastrointestinal tract (very low concentrations in feces), but there is no evidence of enterohepatic recirculation. Quantitation of the three moieties in stool samples accounted for only 1.2% of an administered dose, suggesting that other yet unknown metabolites/degradation products formed through metabolic processes and/or the activity of local microflora are mainly excreted by this route. In man CAG was confirmed as one of the major terminal metabolites of clopidogrel, with a PK behavior similar to CCA.