title: Disposition of a CYP2C9 phenotyping agent, losartan, is not influenced by the common 3435C > T variation of the drug transporter gene ABCB1 (MDR1).
abstract: Losartan is oxidized to E3174 by cytochrome P450 2C9 (CYP2C9); it has been suggested as a useful probe drug for CYP2C9 activity. It has also been shown to be a substrate for the drug-efflux transporter ATP-binding cassette sub-family B member 1 (ABCB1, MDR1). Both CYP2C9 and ABCB1 genes are polymorphic. The aim of the study was to determine if losartan disposition was influenced by the 3435C > T polymorphism of ABCB1 in healthy persons. These participants (n = 58) whose CYP2C9 genotypes and phenotypes were determined previously were genotyped for 3435C > T polymorphism in ABCB1. The concentrations of losartan and E3174 were compared across genotypes for ABCB1 3435C > T variation. For persons with the ABCB1 3435 CC, CT, TT genotypes, the concentrations (microM, means +/- S.D.) of neither losartan (1.76 +/- 0.87, 1.68 +/- 0.84 and 1.80 +/- 0.85, respectively, P = 0.70) nor E3174 (2.97 +/- 2.49, 2.53 +/- 2.09 and 3.18 +/- 2.75, respectively, P = 0.65) were significantly different. These results suggest that ABCB1 3435C > T polymorphism does not have any influence on losartan disposition. Therefore, ABCB1 3435C > T polymorphism is probably not a confounding factor in the prediction of CYP2C9 activity by using losartan as a probe agent.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Hacettepe University, Ankara, Turkey. uyasar@hacettepe.edu.tr
authors.forename: Umit
authors.initials: U
authors.lastname: Yasar
authors.forename: Melih O
authors.initials: MO
authors.lastname: Babaoglu
authors.forename: Atila
authors.initials: A
authors.lastname: Bozkurt
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D047228:Angiotensin II Type 1 Receptor Blockers / Q000378:metabolism / Q000493:pharmacokinetics* / Q000652:urine; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics; D065729:Cytochrome P-450 CYP2C9; D005260:Female; D006801:Humans; D019808:Losartan / Q000378:metabolism / Q000493:pharmacokinetics* / Q000652:urine; D008297:Male; D008875:Middle Aged; D012150:Polymorphism, Restriction Fragment Length; D014018:Tissue Distribution
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D047228:Angiotensin II Type 1 Receptor Blockers; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; D019808:Losartan