title: Site-specific immunosuppression using a new formulation of topical cyclosporine A with polyethylene glycol-8 glyceryl caprylate/caprate.
abstract: OBJECTIVE
  Dermal application of immunosuppressants can be an effective means of achieving site-specific immunosuppression (SITE) on skin allografts in burn wound management and in the treatment of various immune skin disorders. We have previously reported success with topical cyclosporine A (tCsA) in the treatment of skin allograft rejection in rats. Using a new tCsA formulation with a penetration enhancer (PE), polyethylene glycol-8 (PEG-8) glyceryl caprylate/caprate (Labrasol, Gattefossé, St. Priest, France), in a trinary drug delivery system, we hypothesized that we would induce SITE and significantly delay rejection of dual skin allografts in rats.
  
  
  METHODS
  Dual rat skin allografts from Lewis x Brown-Norway (LBN) donors were grafted to Lewis (Lew) recipients. Experimental animals (EXP, n = 7) received a 10-day course of systemic cyclosporine (sCsA, 8 mg/kg/day) followed by topical application. One of the two allografts on each experimental animal received tCsA/PE application (5 mg/kg/day) until sacrifice (tCsA/PE-treated). The other allograft received vehicle only (vehicle-treated). Allogeneic controls (ALLO-CON, n = 9) received no sCsA or tCsA. First signs of rejection were determined based on the initial observation of erythema, hair loss, flakiness, and/or scabs.
  
  
  RESULTS
  The mean time to rejection for ALLO-CON allografts was 6.3 +/- 0.7 days (t test, P = 0.0013); for vehicle-treated allografts, 12.3 +/- 3.8 days (paired t test, P = 0.0146); and for tCsA/PE-treated allografts, 25.6 +/- 5.4 days. The disparity of days to rejection between dual allografts in the ALLO-CON group was 0.0 +/- 0.0 day and that between the tCsA/PE- and vehicle-treated dual allografts was 13.3 +/- 3.9 days (t test, P = 0.0016).
  
  
  CONCLUSIONS
  A new formulation of tCsA in a trinary drug delivery system is successful at delaying the onset of rejection in dual skin allografts in rats by SITE, and PEG-8 glyceryl caprylate/caprate may represent a potentially effective transdermal penetration enhancer.
mesh_terms: D000287:Administration, Topical; D000818:Animals; D002056:Burns / Q000601:surgery; D002210:Caprylates; D016572:Cyclosporine / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000627:therapeutic use*; D006084:Graft Rejection / Q000276:immunology; D006085:Graft Survival / Q000187:drug effects*; D007165:Immunosuppression Therapy; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D011092:Polyethylene Glycols; D051381:Rats; D011914:Rats, Inbred BN; D011917:Rats, Inbred Lew; D012871:Skin Diseases / Q000276:immunology / Q000601:surgery; D016038:Skin Transplantation / Q000276:immunology*; D014184:Transplantation, Homologous