Chitosan as an ocular drug delivery vehicle for vancomycin

The main objective of this research has been to study the efficiency of chitosan as an ocular drug delivery vehicle for topically applied vancomycin in rabbit eyes. Vancomycin 50 mg/mL was reconstituted in four preparations, namely: in Tears Naturale II?, in 0.9% w/v aqueous sodium chloride, and in 0.1% and 0.3% w/v chitosan solutions in 1% aqueous L (+)‐lactic acid. Twenty‐five microliters of vancomycin (50 mg/mL) were applied into the lower conjunctival eye sac in rabbit eyes. Tear samples were then collected after 0, 30, 60, 90, and 120 min to evaluate the pharmacokinetics of the topically applied vancomycin. Comparison of the results obtained showed that vancomycin 50 mg/mL eye drops in the 0.3% chitosan solution were similar to Tears Naturale II? in terms of bioavailability. The main conclusion to be drawn from this study is that the 0.3% w/v chitosan solution appears to be a highly promising, cost effective candidate for biomedical use as a vehicle for vancomycin ocular drug delivery. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Release characteristics of the matrices prepared from co-spray-dried powders of theophylline and ethylcellulose

Co-spray-dried powders of theophylline and ethylcellulose were prepared using aqueous ethylcellulose dispersion. Co-spray-dried powders were directly compressed into the matrices and the release characteristics of the prepared matrices were investigated. The co-spray-dried powders exhibited good matrix formations with high hardness at rather low compression force. The concentration of ethylcellulose in the matrices was, as expected, the rate-determining factor in controlling the release rate of the drug. Increasing the weight fractions of ethylcellulose resulted in a corresponding decrease in the drug release rates in both 0.1 N HCl and phosphate buffer pH 6.8. However, at the same level of ethylcellulose content, the drug release in acidic conditions was higher than in alkaline medium. To modify release characteristics of the matrices, PVP K30 and lactose were employed as channeling agents. At concentrations of 5 and 10%, PVP K30 was found to slow the drug release when incorporated into the co-spray-dried powder formulations containing 5% ethylcellulose. Lactose at a concentration of 15% provided an increasing effect on drug release when added in the formulations. But an increase in lactose quantity from 15 to 25% did not exert much more influence on release characteristics. Higuchi plots were found to be best applicable to all release data. Scanning electron microscopic examinations on the surface and cross-section of the matrices before and after subjection to release testing revealed the formation of porous networks within the matrices by the ethylcellulose fibers. Such polymeric networks would account for the controlled diffusion of the drug from the matrices.