title: Evolution of the absorption profile of cyclosporine A in renal transplant recipients: a longitudinal study of the de novo and maintenance phases.
abstract: BACKGROUND
  Therapeutic drug monitoring for cyclosporine microemulsion (CsA-ME) is often performed using either trough levels (C0) or levels at 2 h post-dose (C2). This analysis assessed changes in C0 and C2 and their relationship to CsA-ME dose over time post-transplant in renal transplant patients.
  
  
  METHODS
  Data were obtained from MO2ART, a prospective multicentre trial in which CsA-ME dose was adjusted based on C2 level. All 98 patients in whom C0 and C2 were available at day 5, month 3 and month 12 were included, out of 234 who completed the 12 month study. Normalized dose (ND) of CsA-ME, defined as dose per kilogram body weight, was calculated, together with C0/ND, C2/ND and C2/C0.
  
  
  RESULTS
  C0/ND and C2/ND both increased between day 5 and month 3: C0/ND from 33+/-15 to 53+/-24 (ng/ml)/(mg/kg) and C2/ND from 161+/-64 to 248+/-80 (ng/ml)/(mg/kg). Between month 3 and month 12, C2/ND remained stable but C0/ND decreased to 42+/-20 (ng/ml)/(mg/kg) while the C2/C0 ratio increased from 5.2+/-1.9 to 6.5+/-2.3, indicating an acceleration of drug elimination. The inter-individual coefficient of variation was higher for C0/ND than for C2/ND at 3 months (45 vs 32%, P<0.05) and at 12 months (48 vs 31%, P<0.01).
  
  
  CONCLUSIONS
  CsA clearance accelerates between months 3 and 12 post-transplant, resulting in lower C0 levels for a given exposure (as measured by C2). As a consequence, C0 monitoring may progressively underestimate CsA exposure during the first year post-transplant. C2 monitoring contributes to improved individualized CsA-ME treatment in both the de novo phase and beyond month 3.
authors.affiliation: Department of Nephrology and Clinical Immunology, C.H.U. Tours, 2 Boulevard Tonnellé 37044 Tours, France, and Royal Prince Alfred Hospital, Sydney, Australia. buchler@med.univ-tours.fr
authors.forename: Matthias
authors.initials: M
authors.lastname: Büchler
authors.forename: Steve
authors.initials: S
authors.lastname: Chadban
authors.forename: Edward
authors.initials: E
authors.lastname: Cole
authors.forename: Karsten
authors.initials: K
authors.lastname: Midtvedt
authors.forename: Eric
authors.initials: E
authors.lastname: Thervet
authors.forename: Hans
authors.initials: H
authors.lastname: Prestele
authors.forename: Paul
authors.initials: P
authors.lastname: Keown
mesh_terms: D000368:Aged; D016572:Cyclosporine / Q000493:pharmacokinetics* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006084:Graft Rejection; D006085:Graft Survival / Q000187:drug effects; D006801:Humans; D007166:Immunosuppressive Agents / Q000493:pharmacokinetics / Q000627:therapeutic use; D007676:Kidney Failure, Chronic / Q000175:diagnosis / Q000276:immunology / Q000601:surgery*; D016030:Kidney Transplantation / Q000276:immunology / Q000379:methods*; D008137:Longitudinal Studies; D008297:Male; D020714:Maximum Tolerated Dose; D008875:Middle Aged; D011336:Probability; D011446:Prospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D013997:Time Factors; D014181:Transplantation Immunology
chemical_list: D007166:Immunosuppressive Agents; D016572:Cyclosporine