title: Topically applied methotrexate is rapidly delivered into skin by fractional laser ablation.
abstract: OBJECTIVE
  Methotrexate (MTX) is a chemotherapeutic and anti-inflammatory drug that may cause systemic adverse effects. This study investigated kinetics and biodistribution of MTX delivered topically by ablative fractional laser (AFXL).
  
  
  METHODS
  In vitro passive diffusion of 10 mg/ml MTX (1 w/v%) was measured from 0.25 to 24 h through AFXL-processed and intact porcine skin in Franz Cells (n = 46). A 2,940 nm fractional Erbium Yttrium Aluminium Garnet laser generated mid-dermal microchannels at 2.4% density, and 256 mJ/microchannel. HPLC quantified MTX-concentrations in extracts from mid-dermal skin sections, donor and receiver compartments. Fluorescence microscopy of UVC-activated MTX-fluorescence and desorption electro-spray ionization mass spectrometry imaging (DESI-MSI) evaluated MTX biodistribution.
  
  
  RESULTS
  AFXL-processed skin facilitated rapid MTX delivery through cone-shaped microchannels of 690 µm ablation depth, lined by the 47 µm thermal coagulation zone (CZ). Quantitatively, MTX was detectable by HPLC in mid-dermis after 15 min, significantly exceeded deposition in intact skin after 1.5 h, and saturated skin after 7 h at a 10-fold increased MTX-deposition versus intact skin (3.08 vs 0.30 mg/cm(3), p = 0.002). Transdermal permeation was < 1.5% of applied MTX before skin saturation, and increased up to 8.0% after 24 h. Qualitatively, MTX distributed into CZ within 15 min (p = 0.015) and further into surrounding dermal tissue after 1.5 h (p = 0.004). After skin saturation at 7 h, MTX fluorescence intensities in CZ and tissue were similar and DESI-MSI confirmed MTX biodistribution throughout the mid-dermal skin section.
  
  
  CONCLUSIONS
  MTX absorbs rapidly into mid-dermis of AFXL-processed skin with minimal transdermal permeation until skin saturation, suggesting a possible alternative to systemic MTX for some skin disorders.
authors.affiliation: Bispebjerg University Hospital, University of Copenhagen, Department of Dermatology , Bispebjerg Bakke 23, DK-2400 Copenhagen NV , Denmark +45 35 31 60 04 ; ehtaudorf@dadlnet.dk.
authors.forename: Elisabeth Hjardem
authors.initials: EH
authors.lastname: Taudorf
authors.forename: Catharina Margrethe
authors.initials: CM
authors.lastname: Lerche
authors.forename: Anne-Cathrine
authors.initials: AC
authors.lastname: Vissing
authors.forename: Peter Alshede
authors.initials: PA
authors.lastname: Philipsen
authors.forename: Jens
authors.initials: J
authors.lastname: Hannibal
authors.forename: Janina
authors.initials: J
authors.lastname: D'Alvise
authors.forename: Steen Honore
authors.initials: SH
authors.lastname: Hansen
authors.forename: Christian
authors.initials: C
authors.lastname: Janfelt
authors.forename: Uwe
authors.initials: U
authors.lastname: Paasch
authors.forename: Richard Rox
authors.initials: RR
authors.lastname: Anderson
authors.forename: Merete
authors.initials: M
authors.lastname: Haedersdal
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D005260:Female; D053685:Laser Therapy; D053844:Lasers, Solid-State; D008727:Methotrexate / Q000008:administration & dosage* / Q000493:pharmacokinetics; D008856:Microscopy, Fluorescence; D012867:Skin / Q000378:metabolism*; D012869:Skin Absorption; D013552:Swine; D014018:Tissue Distribution
chemical_list: D008727:Methotrexate
keywords: desorption electro-spray ionization mass spectrometry imaging; fluorescence microscopy; fractional erbium laser; franz skin permeability cells; high performance liquid chromatography; laser-assisted drug delivery