title: Erythromycin breath test predicts oral clearance of cyclosporine in kidney transplant recipients.
abstract: It has been shown recently that cyclosporine is largely metabolized by P450IIIA (CYP3A), an enzyme whose catalytic activity varies significantly among patients. To determine whether heterogeneity in P450IIIA activity contributes to interpatient differences in cyclosporine dosing requirements, the oral pharmacokinetics of the drug were determined in 20 stable kidney transplant recipients. P450IIIA activity was then measured in each patient by use of the erythromycin breath test. In the 16 patients who were at steady state, the logarithm of the apparent oral clearance of cyclosporine correlated significantly with the rate of 14CO2 exhaled in breath after intravenous administration of [14C N-methyl]erythromycin (r = 0.55, p = 0.03). No significant correlations existed between apparent oral clearance and age, high-density lipoprotein cholesterol or low-density lipoprotein cholesterol, or hematocrit in these patients. We conclude that heterogeneity in P450IIIA activity significantly contributes to interpatient differences in dosing requirements of cyclosporine in kidney transplant patients.
authors.affiliation: Department of Medicine, University of Michigan, Ann Arbor 48109.
authors.forename: D K
authors.initials: DK
authors.lastname: Turgeon
authors.forename: D P
authors.initials: DP
authors.lastname: Normolle
authors.forename: A B
authors.initials: AB
authors.lastname: Leichtman
authors.forename: T M
authors.initials: TM
authors.lastname: Annesley
authors.forename: D E
authors.initials: DE
authors.lastname: Smith
authors.forename: P B
authors.initials: PB
authors.lastname: Watkins
mesh_terms: D000328:Adult; D001944:Breath Tests / Q000379:methods; D002245:Carbon Dioxide / Q000378:metabolism; D002250:Carbon Radioisotopes; D016572:Cyclosporine / Q000493:pharmacokinetics*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004917:Erythromycin; D005260:Female; D006801:Humans; D016030:Kidney Transplantation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D013250:Steroid Hydroxylases / Q000378:metabolism
chemical_list: D002250:Carbon Radioisotopes; D002245:Carbon Dioxide; D004917:Erythromycin; D016572:Cyclosporine; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; C022657:steroid hormone 6-beta-hydroxylase