title: Myocardial pharmacokinetics of ebastine, a substrate for cytochrome P450 2J, in rat isolated heart.
abstract: OBJECTIVE
  It is well established that cytochrome P450 2J (CYP2J) enzymes are expressed preferentially in the heart, and that ebastine is a substrate for CYP2J, but it is not known whether ebastine is metabolized in myocardium. Therefore, we investigated its pharmacokinetics in the rat isolated perfused heart.
  
  
  METHODS
  Rat isolated hearts were perfused in the recirculating mode with ebastine for 130 min. The concentrations of ebastine and its metabolites, hydroxyebastine and carebastine, were measured using liquid chromatography with a tandem mass spectrometry. The data were analysed by a compartmental model. The time course of negative inotropic response was linked to ebastine concentration to determine the concentration-effect relationship.
  
  
  RESULTS
  Ebastine was metabolized to an intermediate compound, hydroxyebastine, which was subsequently further metabolized to carebastine. No desalkylebastine was found. The kinetics of the sequential metabolism of ebastine was well described by the compartmental model. The EC(50) of the negative inotropic effect of ebastine in rat isolated heart was much higher than free plasma concentrations in humans after clinical doses.
  
  
  CONCLUSIONS
  The kinetics of ebastine conversion to carebastine via hydroxyebastine resembled that observed in human liver microsomes. The results may be of interest for functional characterization of CYP2J activity in rat heart.
authors.affiliation: College of Pharmacy, Yeungnam University, Kyoungbuk, South Korea Section of Pharmacokinetics, Department of Pharmacology, Martin Luther University Halle-Wittenberg, Halle, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Kang
authors.forename: S
authors.initials: S
authors.lastname: Elitzer
authors.forename: K
authors.initials: K
authors.lastname: Noh
authors.forename: T
authors.initials: T
authors.lastname: Bednarek
authors.forename: M
authors.initials: M
authors.lastname: Weiss
mesh_terms: D000818:Animals; D002090:Butyrophenones / Q000378:metabolism / Q000493:pharmacokinetics* / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000502:physiology*; D006321:Heart / Q000187:drug effects*; D006634:Histamine H1 Antagonists / Q000378:metabolism / Q000493:pharmacokinetics* / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008956:Models, Chemical; D009206:Myocardium / Q000378:metabolism*; D010880:Piperidines / Q000378:metabolism / Q000493:pharmacokinetics* / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002090:Butyrophenones; D006634:Histamine H1 Antagonists; D010880:Piperidines; D003577:Cytochrome P-450 Enzyme System; C058249:ebastine