In vitro release studies of azithromycin from chitosan gels

Cilj ovog rada bila je priprava kitozanskih gelova s uklopljenim azitormicinom te ispitivanje in vitro oslobađanja lijeka iz dobivenih formulacija. Uspješan razvoj formulacije omogućio bi dermalnu primjenu azitromicina koji je zbog svog širokog spektra djelovanja često dio oralne terapije bakterijskih kožnih oboljenja. Pripremljeni su hidrogelovi s različitim tipovima kitozana s obzirom na molekulsku masu (niskomolekulski, srednjemolekulski, visokomolekulski), te s različitim udjelima kitozana i različitim udjelima octene kiseline. Provedena je i titracija pH vrijednosti dobivenih gelova kako bi se postigla optimalna pH vrijednost (pH=6). Zbog zadovoljavajućih reoloških svojstava za in vitro ispitivanje oslobađanja uklopljenog azitromicina odabran je srednjemolekulski kitozanski gel s 1,5%, 2% i 2,5% kitozana. In vitro ispitivanje oslobađanja azitromicina iz hidrogelova u koje je umiješana otopina lijeka (30%, m/m) provedeno je na Franz-difuzijskoj ćeliji tijekom 24 sata. Sadržaj oslobođenog azitromicina određen je pomoću tekućinske kromatografije visoke djelotvornosti (high performance liquid chromatography, HPLC). Dobiveni rezultati pokazuju da se najveći udio azitromicina (%) oslobodio iz hidrogela s najmanjim udjelom kitozana (1,5%-tni MMW). Potvrđeno je da je oslobađanje azitromicina iz kitozanskih hidrogelova ovisno o njihovoj viskoznosti koja je određena sadržajem kitozana u gelu i pH vrijednosti gela.The aim of this study was development and evaluation of chitosan-based hydrogels with azithromycin. Successful development of topical skin formulation would enable dermal application of azythromycin which is, due to its wide range of antibacterial activities, commonly used for the treatment of bacterial skin infections via oral route of administration. Hydrogels containing different types of chitosan (low molecular weight, medium molecular weight and high molecular weight chitosan), different weights of chitosan and different amounts of acetic acid have been prepared. In order to optimize pH of the gels (pH 6) triethanolamin was applied as neutralizing agent. Considering appropriate viscosities of the gel, 1,5%, 2% and 2,5% medium molecular weight chitosan gels were chosen for investigation of the in vitro release of azithromycin entrapped in the hydrogels. In vitro release studies were performed during 24 h using Franz diffusion cell system. The release of azithromycin from different hydrogels containing 30% of drug solution (3μg/ml) was tested. The amount of the released azithromycin was determined chromatographically (HPLC). The largest amount of azithromycin was released from hydrogel with the lowest chitosan concentration (1,5%). It can be concluded that the release of azithromycin from chitosan hydrogel formulations depends on their viscosity which is directly influenced by chitosan concentration and pH of the gel