Clobetasol-17-propionate (CP) was a kind gift from GlaxoSmithKline (Ankara, Turkey). Lecithin (Lipoid S45) was purchased from Lipoid AG (Ludwigshafen, Germany) and chitosan (Chitoclear FG, specifications: deacetylation degree 95%, viscosity 93 cP for 1% w/v solution in 1% v/v acetic acid) for nanoparticles preparation was from Primex (Haugesund, Norway). Medium molecular weight chitosan (specifications: MW 190-310 kDa, deacetylation degree 75%–85%, viscosity 200–800 cP for 1% w/v solution in 1% v/v acetic acid) for gel preparation as well as λ carrageenan used for hind paw test was obtained from Sigma-Aldrich (St. Louis, MO, USA). Polyethylene glycol 400 (PEG 400) and mannitol were provided from Merck (Darmstadt, Germany). Sodium deoxycholate (Na-DOC) was purchased from Fluka (Munich, Germany). All other chemicals were of analytical grade.