title: Comparative performance of oral midazolam clearance and plasma 4β-hydroxycholesterol to explain interindividual variability in tacrolimus clearance.
abstract: We compared the CYP3A4 metrics weight-corrected midazolam apparent oral clearance (MDZ Cl/F/W) and plasma 4β-hydroxycholesterol/cholesterol (4β-OHC/C) as they relate to tacrolimus (TAC) Cl/F/W in renal transplant recipients.
  
  
  
  For a cohort of 147 patients, 8 h area under the curve (AUC) values for TAC and oral MDZ were calculated besides measurement of 4β-OHC/C. A subgroup of 70 patients additionally underwent intravenous erythromycin breath test (EBT) and were administered the intravenous MDZ probe. All patients were genotyped for common polymorphisms in CYP3A4, CYP3A5 and P450 oxidoreductase, among others.
  
  
  
  MDZ Cl/F/W, 4β-OHC/C/W, EBT and TAC Cl/F/W were all moderately correlated (r = 0.262-0.505). Neither MDZ Cl/F/W nor 4β-OHC/C/W explained variability in TAC Cl/F/W in CYP3A5 expressors (n = 29). For CYP3A5 non-expressors (n = 118), factors explaining variability in TAC Cl/F/W in a MDZ-based model were MDZ Cl/F/W (R2= 0.201), haematocrit (R2= 0.139), TAC formulation (R2= 0.107) and age (R2= 0.032; total R2= 0.479). In the 4β-OHC/C/W-based model, predictors were 4β-OHC/C/W (R2= 0.196), haematocrit (R2= 0.059) and age (R2= 0.057; total R2= 0.312). When genotype information was ignored, predictors of TAC Cl/F/W in the whole cohort were 4β-OHC/C/W (R2= 0.167), MDZ Cl/F/W (R2= 0.045); Tac QD formulation (R2= 0.036), and haematocrit (R2= 0.032; total R2= 0.315). 4β-OHC/C/W, but not MDZ Cl/F/W, was higher in CYP3A5 expressors because it was higher in CYP3A4*1b carriers, which were almost all CYP3A5 expressors.
  
  
  
  A MDZ-based model explained more variability in TAC clearance in CYP3A5 non-expressors. However, 4β-OHC/C/W was superior in a model in which no genotype information was available, likely because 4β-OHC/C/W was influenced by the CYP3A4*1b polymorphism.
authors: Department of Microbiology and Immunology, KU Leuven - University of Leuven, Leuven, Belgium.|Department of Nephrology and Renal Transplantation, University Hospitals Leuven, Leuven, Belgium.
authors: Thomas
authors: 0000-0001-5712-6294
authors: T
authors: Vanhove
authors: Department of Microbiology and Immunology, KU Leuven - University of Leuven, Leuven, Belgium.|Department of Nephrology and Renal Transplantation, University Hospitals Leuven, Leuven, Belgium.
authors: Hylke
authors: H
authors: de Jonge
authors: Department of Nephrology and Renal Transplantation, University Hospitals Leuven, Leuven, Belgium.
authors: Henriëtte
authors: H
authors: de Loor
authors: Drug Delivery and Disposition, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven - University of Leuven, Leuven, Belgium.
authors: Pieter
authors: P
authors: Annaert
authors: Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors: Ulf
authors: U
authors: Diczfalusy
authors: Department of Microbiology and Immunology, KU Leuven - University of Leuven, Leuven, Belgium.|Department of Nephrology and Renal Transplantation, University Hospitals Leuven, Leuven, Belgium.
authors: Dirk R J
authors: DR
authors: Kuypers
mesh_terms: D000284:Administration, Oral; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D051544:Cytochrome P-450 CYP3A / Q000235:genetics*; D005260:Female; D005838:Genotype; D006801:Humans; D006888:Hydroxycholesterols / Q000097:blood*; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D007275:Injections, Intravenous; D016030:Kidney Transplantation; D008297:Male; D008657:Metabolic Clearance Rate / Q000235:genetics; D008874:Midazolam / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008875:Middle Aged; D011237:Predictive Value of Tests; D016559:Tacrolimus / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D006888:Hydroxycholesterols; D007166:Immunosuppressive Agents; C099828:cholest-5-ene-3,4-diol; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D008874:Midazolam; D016559:Tacrolimus
keywords: 4β-hydroxycholesterol; CYP3A4; CYP3A5; kidney transplantation; midazolam; tacrolimus