Cationic Eudragit® polymers as excipients for microparticles prepared by solvent evaporation method.

Three cationic acrylic polymers, i. e. Eudragit® RL, Eudragit® RS and Eudragit® E 100, were evaluated for the purpose of microparticles preparation by the solvent evaporation method. The practically insoluble drug mirtazapine and the freely soluble drug tramadol hydrochloride were selected for encapsulation as extreme limits of drug solubility. The prepared microspheres were analyzed by optical microscopy, drug content analysis and dissolution test. It was observed that Eudragit® RL did not provide microparticles while Eudragit® RS and Eudragit® E 100 yielded spherical microparticles. Samples prepared with mirtazapine showed sustained drug release whereas tramadol hydrochloride samples released the drug in a pattern similar to the immediate release profile. Eudragit® RS was found to be superior to Eudragit® E 100 in its encapsulation efficiency, drug loading and smaller mean size of microparticles.