title: Biliary excretion of technetium-99m-sestamibi in wild-type dogs and in dogs with intrinsic (ABCB1-1Delta mutation) and extrinsic (ketoconazole treated) P-glycoprotein deficiency.
abstract: P-glycoprotein (P-gp), the product of ABCB1 gene, is thought to play a role in the biliary excretion of a variety of drugs, but specific studies in dogs have not been performed. Because a number of endogenous (ABCB1 polymorphisms) and exogenous (pharmacological P-gp inhibition) factors can interfere with normal P-gp function, a better understanding of P-gp's role in biliary drug excretion is crucial in preventing adverse drug reactions and drug-drug interactions in dogs. The objectives of this study were to compare biliary excretion of technetium-99m-sestamibi ((99m)Tc-MIBI), a radio-labelled P-gp substrate, in wild-type dogs (ABCB1 wild/wild), and dogs with intrinsic and extrinsic deficiencies in P-gp function. Dogs with intrinsic P-gp deficiency included ABCB1 mut/mut dogs, and dogs with presumed intermediate P-gp phenotype (ABCB1 mut/wild). Dogs with extrinsic P-gp deficiency were considered to be ABCB1 wild/wild dogs treated with the P-gp inhibitor ketoconazole (5 mg/kg PO q12h x 9 doses). Results from this study indicate that ABCB1 mut/mut dogs have significantly decreased biliary excretion of (99m)Tc-MIBI compared with ABCB1 wild/wild dogs. Treatment with ketoconazole significantly decreased biliary excretion of (99m)Tc-MIBI in ABCB1 wild/wild dogs. P-gp appears to play an important role in the biliary excretion of (99m)Tc-MIBI in dogs. It is likely that concurrent administration of a P-gp inhibitor such as ketoconazole will decrease P-gp-mediated biliary excretion of other substrate drugs as well.
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Coelho
authors.forename: R
authors.initials: R
authors.lastname: Tucker
authors.forename: J
authors.initials: J
authors.lastname: Mattoon
authors.forename: G
authors.initials: G
authors.lastname: Roberts
authors.forename: D K
authors.initials: DK
authors.lastname: Waiting
authors.forename: K L
authors.initials: KL
authors.lastname: Mealey
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000172:deficiency* / Q000235:genetics; D000818:Animals; D001646:Bile; D004285:Dogs / Q000235:genetics / Q000378:metabolism*; D004347:Drug Interactions; D005260:Female; D005704:Gallbladder / Q000187:drug effects / Q000502:physiology; D015902:Gamma Cameras; D007654:Ketoconazole / Q000494:pharmacology*; D008297:Male; D011110:Polymorphism, Genetic; D017256:Technetium Tc 99m Sestamibi / Q000493:pharmacokinetics*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D017256:Technetium Tc 99m Sestamibi; D007654:Ketoconazole