IN-VITRO RELEASE OF TIMOLOL MALEATE FROM AN IN-SITU GELLING POLYMER SYSTEM

A thermogelling drug delivery system composed of a cellulose ether (ethyl(hydroxyethyl)cellulose - EHEC), an ionic surfactant and water was thoroughly characterized in the presence of timolol maleate with respect to phase and rheological behaviour, as well as in vitro drug release. The phase studies reveal that gelling systems may be formed with 0.34% (w/w) timolol maleate, and that the gelling behaviour is sensitive to the surfactant concentration and ionic strength of the solution. The release of timolol maleate from the gels is retarded compared to a non-gelling EHEC system. The release rate is about equal for systems with 1 and 2% (w/w) EHEC, implying that the release is controlled by a low convection in the gels and not by any drug-polymer interaction.