Physico-chemical characterization of interactions between erythromycin andvarious film polymers

In this study the interactions between erythromycin and various polymers (E udragit L100, shellac, polyvinyl acetate phthalate (PVAP), cellulose acetat e phthalate (CAP), hydroxypropyl methylcellulose acetate phthalate (HPMCP), and hydroxypropyl methylcellulose (HPMC)) were investigated. The polymer f ilms containing drugs were prepared and characterized by the use of infrare d spectroscopy, powder X-ray diffraction analysis, thermal analysis, thin l ayer chromatography, and nuclear magnetic resonance (NMR) spectroscopy. Pre liminary studies of pure drug powders recrystallized in various organic sol vent systems suggested a mixture of amorphous and crystalline forms whereas those recrystallized in water and organic solvent-water mixture led to the dihydrate form. Erythromycin in drug-polymer mixtures exhibited molecular dispersions in all six polymers studied. The amine salt interaction between the carboxyl group of the acid polymers and N-atom of erythromycin was ind icated by the NMR technique. The solid solution of erythromycin in all poly mer films studied was physically stable under stress conditions (8 degrees C/3 days and 40 degrees C/3 days for six cycles). (C) 1999 Elsevier Science B.V. All rights reserved.