Controlled release polymeric ocular delivery of acyclovir.

The aim of the present study was to formulate and evaluate controlled release polymeric ocular delivery of acyclovir. Reservoir-type ocular inserts were fabricated by sandwiching hydroxypropyl methylcellulose (HPMC) matrix film containing acyclovir between two rate controlling membranes of cellulose acetate phthalate (CAP). The solubility and dissolution rate of poorly soluble acyclovir was enhanced by preparing binary systems with beta-cyclodextrin and then incorporated into HPMC matrix. Nine formulations (AB-1 to AB-9) with varying ratio of HPMC (drug matrix) and CAP (rate controlling membrane) were developed and sterilized by gamma radiation. The formulations were subjected to various physico-chemical evaluations. The in vitro release profile of all the formulations showed a steady, controlled drug release up to 20 h with non-Fickian diffusion behavior. A high correlation coefficient found between in vitro/in vivo release rate studies. Formation of acyclovir complex was confirmed by differential scanning calorimetry. In addition, dissolution rate studies revealed improved solubility of acyclovir when complexed with beta-cyclodextrin. Stability studies showed that the ocular inserts could be stored safely at study storage conditions. In conclusion, the present study demonstrated controlled release formulation of acyclovir inserts for ocular delivery using biodegradable polymers.

Glutaraldehyde cross-linked chitosan microspheres for controlled delivery of zidovudine.

Zidovudine-Chitosan microspheres were prepared by a suspension cross-linking method. The chitosan was dissolved in 2% acetic acid solution and this solution was dispersed in the light liquid paraffin. Span-80 was used as an emulsifier and glutaraldehyde as cross-linking agent. The prepared microspheres were slight yellow, free flowing and characterized by drug loading, infrared spectroscopy (IR), differential scanning colorimetry (DSC) and scanning electron microscopy (SEM). The in-vitro release studies are performed in pH 7.4 buffer solution. Microspheres produced are spherical and have smooth surfaces, with sizes ranging between 60-210 µm, as evidenced by SEM and particle size analysis. The drug loaded microspheres showed up to 60% of entrapment and release was extended up to 18-24 h. Among all the systems studied, the 35% Glutaraldehyde crosslinked, microspheres with 1 : 6 drug/chitosan ratio showed 75% release at 12 h. The infrared spectra and DSC thermograms showed stable character of zidovudine in the drug loaded microspheres and revealed the absence of drug-polymer interactions. Data obtained from in vitro release were fitted to various kinetic models and high correlation was obtained in the Higuchi model. The drug release was found to be diffusion controlled.