Controlled release microspheres based on Eudragit L100 for the oral administration of erythromycin.

The use of Eudragit L100, a copolymer based on methacrylic acid and methacrylic acid methyl ester, in preparing erythromycin microspheres is described. The microspheres were simply prepared in liquid paraffin by solidifying an Eudragit L100 in ethanol solution. When gelatin was incorporated in the solidifying solution, the resultant microspheres were more spherical and had a smooth surface. The size of the microspheres could be controlled by varying the Eudragit L100 concentration in ethanol, and erythromycin was incorporated with 60-70% efficiency. The degradation of erythromycin by acid was markedly protected when the erythromycin microspheres were coated with the polymer. The in vitro release rate of erythromycin from the microspheres was also modified by the coating process. The feasibility of preparing formulations of erythromycin for oral administration, which release the drug at a controlled rate, and protect the drug from gastric acid, is thus demonstrated.