In vitro evaluation of polyethylene glycol based microparticles containing azithromycin

The objectives of the present investigation are (1) to screen the liquid and solid polyethylene glycol (PEG) molecules able to produce microparticles by cold or hot dispersion method either with or without other excipients, and (2) to evaluate the in vitro activities [like thermodegradation at three different storage conditions, dissolution using a membrane-free dissolution model in artificial tear fluid or phosphate buffer solution of pH 7.4, and zone-inhibition assay using Eschericella coli and red blood cells (RBC) rupturing assay] of azithromycin (AZM)-loaded microparticles in comparison to AZM alone. Adding chitosan and propylene glycol into PEG 6000 led to the formation of spherical-shaped microparticles. Keeping the drug alone in phosphate buffer solution of pH 7.4 at three different storage conditions did show degradation and thus precipitation whereas incorporating the drug into microparticles did not. The microparticles showed a drug release profile that was completely in a retarded style when compared to the release profile of drug alone. The antimicrobial activity of AZM was not affected after incorporating it into microparticles as shown in the zone-inhibition assay. Nevertheless, the microparticles reduced markedly the RBC rupturing property of the drug in comparison to drug in phosphate buffer solution of pH 7.4 (hemolysis percentage values of 27.41 ± 4.1and 43.11 ± 7.6, respectively). This indicates that the microparticles prepared based on PEG, chitosan and propylene glycol could be of a suitable carrier to protect AZM from thermodegradation, to provide retardation in drug release, to preserve antimicrobial activity, and to reduce RBC rupturing effect of the drug.