1. IN VITRO RELEASE STUDY OF TENOXICAM FROM HYDROGELS Tenoxicam is a lipophilic anti-inflammatory agent, very little soluble in water, frequently used in the treatment of rheumatic diseases for its anti-inflammatory and analgesic properties. The experimental study followed the in vitro release of tenoxicam from hydroxypropyl methylcellulose-based hydrogels, as well as the assessment of the effect of formulation variables on the diffusion profile of tenoxicam through synthetic membranes. The release of tenoxicam from hydrogels was influenced by the type of salt which was formed following neutralisation, but the decisive role on the release was played by the presence of 2-hydroxypropyl-β-cyclodextrin in the formulation. Tenoxicam was released at approximately equal speeds from the other formulations, without significant differences due to formulation variables. Materials. Tenoxicam, with purity > 99%, was a generous gift from LaborMed Pharma, (Romania), while β-cyclodextrin (β-CD) (99%) and 2-hydroxypropyl-β-cyclodextrin (2HP-β-CD) with >99% purity (DS~3±1) were received from Cyclolab (Hungary); hydroxypropylmethyl cellulose (HPMC) (Methocel E4 Premium, Colorcon Limited, England); monoethanolamine (MEA) (Stera Chemicals, Bucharest); sodium hydroxide solution 10%; preservative solution (F.R. X); mixed cellulose esters membranes, with pore size 0.45 μm (Millipore, Ireland). Ethanol and other base chemicals of analytical grades were purchased from commercial suppliers and used without further purification. Methods. Two series of 3% hydroxypropyl methylcellulose-based hydrogels were carried out, containing 1% tenoxicam, the neutralising agents used were monoethanolamine (series a) and sodium hydroxide solution 10% (series b). The study of in vitro release through synthetic membrane was conducted with the help of the Franz diffusion cell, the reception environment was represented by the phosphate buffer solution (pH 7,4). The hydrogels were assessed according to pH, viscosity, rheological behaviour, consistency and spreadability. Figure 3. Reograma and viscosity curve of hydrogel T1aFigure 4. The variation of pH for hydrogels based on HPMC Figure 1. Cumulative release kinetic profile of tenoxicam from T1-T6 hydrogels based on HPMC Figure 2. The curves of extensometers HPMC-based hydrogels The in vitro release study has emphasised that tenoxicam was released in the greatest proportion in the 4b formulation, following neutralisation with sodium hydroxide solution 10%, while the slowest release was realised in the 2a formulation (fig.1). All hydrogels displayed appropriate consistency and spreadability (fig.2), thixotropic pseudoplastic character (fig.3), whereas pH values were situated withing the limits imposed by the pharmacopoeia (fig.4). 1a Şuta Lenuţa-Maria, 2 Belu Ionela, 1a Vlaia Lavinia, 1b Fuliaş Adriana, 1c Ledeţi Ionuţ, 1a Hegheş Alina, 1d Trandafirescu Cristina, 1e Suciu Liana, 1d Oprean Camelia, 3 Mircioiu Constantin Objective Material and methods Results Conclusions 1 University of Medicine and Pharmacy “Victor Babeş”, Faculty of Pharmacy, a Department of Pharmaceutical Technology, b Department of Analytical Chemistry, c Department of Physical Chemistry, d Department of Pharmaceutical Chemistry, e Department of Pharmacology, 2 Eftimie Murgu Sq., Timişoara, 300041, Romania 2 University of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Technology, Petru Rares Street, 2-4, Craiova, 200349, Romania 3 University of Medicine and Pharmacy “Carol Davila”, Faculty of Pharmacy, Department of Applied Mathematics and Biostatistics, 6 Traian Vuia St., 020956, Bucharest, Romania