title: Skin and systemic pharmacokinetics of tacrolimus following topical application of tacrolimus ointment in adults with moderate to severe atopic dermatitis.
abstract: BACKGROUND
  Systemic exposure to tacrolimus following topical application of tacrolimus ointment is minimal. There are, however, no data on the distribution of tacrolimus in the skin.
  
  
  OBJECTIVE
  To assess the distribution of tacrolimus in the skin and the systemic pharmacokinetics of tacrolimus in adults with moderate to severe atopic dermatitis after first and repeated application of tacrolimus ointment.
  
  
  METHODS
  We investigated skin distribution of topically applied tacrolimus and systemic pharmacokinetics of percutaneously absorbed tacrolimus in adults with atopic dermatitis after topical application of tacrolimus 0.1% ointment twice daily for 2 weeks. Tacrolimus concentrations were assessed in full-thickness skin biopsies and blood samples.
  
  
  RESULTS
  Of 14 patients, 11 completed treatment and were analysed. Mean +/- SD tacrolimus concentrations in the skin at 24 h after first and last ointment applications were 94 +/- 20 and 595 +/- 98 ng cm(-3), respectively. At 168 h after stopping treatment, values were 97% lower than at 24 h after last application. Tacrolimus concentration decreased with increasing skin depth. Systemic tacrolimus exposure after ointment application was low and highly variable, with 31% of samples below the limit of quantification (0.025 ng mL(-1)) and 94% below 1 ng mL(-1). Blood concentrations at 24 h after the first and last ointment applications were 750 and 1800 times lower, respectively, than those in skin. Physicians' assessments showed that tacrolimus ointment was effective and well tolerated.
  
  
  CONCLUSIONS
  Tacrolimus was primarily partitioned in the skin, with minimal systemic absorption after topical application, in patients with atopic dermatitis.
authors.affiliation: Department of Pharmacokinetics, Astellas Pharma GmbH, 81673 Munich, Germany. nas.undre@eu.astellas.com
authors.forename: N A
authors.initials: NA
authors.lastname: Undre
authors.forename: F J
authors.initials: FJ
authors.lastname: Moloney
authors.forename: S
authors.initials: S
authors.lastname: Ahmadi
authors.forename: P
authors.initials: P
authors.lastname: Stevenson
authors.forename: G M
authors.initials: GM
authors.lastname: Murphy
mesh_terms: D000328:Adult; D000368:Aged; D001706:Biopsy; D003876:Dermatitis, Atopic / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009824:Ointments; D012867:Skin / Q000378:metabolism* / Q000473:pathology; D012869:Skin Absorption; D016559:Tacrolimus / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D007166:Immunosuppressive Agents; D009824:Ointments; D016559:Tacrolimus