title: Are Tacrolimus Pharmacokinetics Affected by Nephrotic Stage?
abstract: Although tacrolimus therapy is not the first-line therapy for childhood nephrotic syndrome, it is often used instead of cyclosporine to ameliorate the side effects. The pharmacokinetics (PK) of tacrolimus (Tac) can be influenced by many conditions, and it has a high plasma protein binding. The Tac PK during relapse and remission of childhood nephrotic syndrome has not been well described.
  
  
  
  We performed 14 PK profiles (with measurements before intake and 0.5, 1, 2, 4, and 12 hours postintake) in 7 children with steroid-resistant nephrotic syndrome at week 1 (all nephrotic) and week 16 after Tac therapy (all in remission). These data were compared with historical PK data of 161 PK profiles in 87 pediatric renal transplant recipients with measurements before intake and 0.5, 1, 1.5, 2, 3, 4, 6, 8, and 12 hours postintake. Tac levels were measured using the Abbott Tacro II assay. We used descriptive statistics to generate percentiles and compared these with those of patients with steroid-resistant nephrotic syndrome.
  
  
  
  The median age of patients with nephrotic syndrome was 3.2 years (range 2.5, 17.2), male gender 71.4%, significantly younger than the control group. Median Tac dose was similar during both PK profiles (0.11 mg·kg·d at week 1 versus 0.13 mg·kg·d at week 16, P = 0.81). There were no statistically significant differences in median dose-normalized area-under-the-time-concentration profiles, peak concentration, time to reach peak concentration, and Tac trough levels. Individual dose-normalized Tac levels for each time point during the PK profile were also not different (P = 0.81).
  
  
  
  We conclude that Tac PK profiles are unaltered during relapse of nephrotic syndrome.
authors.affiliation: *Laboratorio de Investigacion en Nefrologia, Hospital Infantil de Mexico Federico Gomez; †Departamento de Farmacología, Facultad de Medicina, Universidad Nacional Autónoma de México; ‡Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Mexico City, Mexico; §Department of Pediatrics, Children's Hospital, London Health Science Centre; ¶Department of Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry; ‖Department of Medicine, London Health Science Centre, University of Western Ontario, London, Ontario, Canada.
authors.forename: Mara
authors.initials: M
authors.lastname: Medeiros
authors.forename: Saúl
authors.initials: S
authors.lastname: Valverde
authors.forename: Irma
authors.initials: I
authors.lastname: Del Moral
authors.forename: Luis
authors.initials: L
authors.lastname: Velásquez-Jones
authors.forename: Ana María
authors.initials: AM
authors.lastname: Hernández
authors.forename: Gilberto
authors.initials: G
authors.lastname: Castañeda-Hernández
authors.forename: Herlinda
authors.initials: H
authors.lastname: Reyes
authors.forename: Guido
authors.initials: G
authors.lastname: Filler
mesh_terms: D000293:Adolescent; D019540:Area Under Curve; D002648:Child; D002675:Child, Preschool; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008297:Male; D009404:Nephrotic Syndrome / Q000188:drug therapy* / Q000503:physiopathology; D012008:Recurrence; D016559:Tacrolimus / Q000008:administration & dosage / Q000493:pharmacokinetics*; D013997:Time Factors
chemical_list: D007166:Immunosuppressive Agents; D016559:Tacrolimus