1. OBJECTIVES The aim was to develop and adequately characterize, through structural analaysis and in-vitro drug release evaluations, new topical semisolid hydrophilic gels, used for administration of organometalic complexes on skin and mucosa. The hydrophilic semisolid formulations developed based on polyoxyethylene-polyoxypropylene block copolymers showed adequate properties as vehicles for the hydrophobic organometalic complexes. They displayed pseudoplastic behavior, and in- vitro release profiles highly dependent on the solubility within the semisolid matrix. The hysteresis loop test indicated a pseudoplastic character, demonstrated by the applicability of the Ostwald de Waele model and by the values of the flow behavior index lower than 1. The in-vitro release rates were unexpectedly high (in some instances, higher than 1 µg/cm 2 /min 1/2 ), with an apparent dependence on the physico-chemical properties of the complex. Structural and in-vitro release evaluations of poloxamer gel containing metal-oxicam coordination compounds Ana Andreea Stănescu 1, Adina Cimpoieu 2, Adrian A. Andrie 3, Sultana Niă 4, Dalia Simona Miron 5, Flavian Stefan Radulescu 3 University of Medicine and Pharmacy „Carol Davila” Bucharest, 1 Faculty of Pharmacy, Department of Pharmaceutical Technology and Biopharmaceutics, 6, Traian Vuia Street, 020956, Bucharest, Romania. 2 Faculty of Pharmacy, Department of Drug Control, 6, Traian Vuia Street, 020956, Bucharest, Romania. 3 Faculty of Pharmacy, Department of Drug Industry and Pharmaceutical Biotechnologies, 6, Traian Vuia Street, 020956, Bucharest, Romania. 4 National Institute for Chemical Pharmaceutical Research and Development, 112 Calea Vitan, 031299, Bucharest, Romania. 5 Faculty of Medicine, Department of Pharmaceutical Physics and Informatics, 6, Traian Vuia Street, 020956, Bucharest, Romania. Corresponding author: aastanescu@yahoo.com RESULTS AND DISCUSSION CONCLUSIONS REFERENCES [1] Lee CH, Moturi V, Lee Y. Thixotropic property in pharmaceutical formulations. J Control Release. 2009;136(2):88-98. [2] United States Pharmacopoeia 36 - National Formulary 31, First supplement. Chapter. ACKNOWLEDGEMENT This work was supported by the Romanian Partnership Programme PN II - supported by the National Agency for Scientific Research - ANCS, CNDI - UEFISCDI, contract number 126/2012. MATERIALS AND METHODS The first stage was focused on the design of the vehicle and selection of a manufacturing procedure, able to generate a molecular dispersion of the hydrophobic active ingredient (noted Cx1 and Cx2, differening in the type of organic ligand). A hydrophilic polyoxyethylene-polyoxypropylene block copolymers matrix (micronized poloxamer 407, BASF GmbH) was selected, based on the its remarkable biocompatibility. A minimum quantity of cosolvent mixture was added, 10% ethanol absolute and 5% nonionic tensioactive or standardized mixture of surfactants, isopropyl-myristate (F1); Cremophor EL (F2); Saboderm G20 (F3) and Saboderm SHO (F4). The thermosensitive hydrogels were analyzed by a set of correlated tests, including the analysis of the rheological behavior (hysteresis loop test, [1]) and the evaluation of in-vitro release profiles using a vertical diffusion cell system [2]. Figure 1.Figure 2. Release rate (µg/cm 2 /min 1/2 ) 0,790,410,490,62 Lag time (min 1/2 )0,800,520,223,56 R2R2 0,99660,99270,99780,9926 Release rate (µg/cm 2 /min 1/2 ) 1,110,661,310,24 Lag time (min 1/2 )6,449,176,355,25 R2R2 0,99570,94790,99850,9914 Table 1. Parameters of the Higuchi model applied to in-vitro release profile of Cx1 Table 2. Parameters of the Higuchi model applied to in-vitro release profile of Cx2 Figure 3.Figure 4. Figure 5.Figure 6.