Jameela, SRKumary, TVLal, AVJayakrishnan, A2012-12-042012-12-041998JOURNAL OF CONTROLLED RELEASE. 52; 40910; 17-24http://dx.doi.org/10.1016/S0168-3659(97)00187-9https://dspace.sctimst.ac.in/handle/123456789/939Smooth, highly spherical, crosslinked chitosan microspheres in the size range of 45-300 mu m loaded with progesterone were prepared by glutaraldehyde crosslinking of an aqueous acetic acid dispersion of chitosan containing progesterone in a non-aqueous dispersion medium consisting of liquid paraffin and petroleum ether stabilized using sorbitan sesquioleate. Ln vitro release of the drug into phosphate buffer at 37 degrees C was determined as a function of crosslinking density of the microspheres and particle size. The extent of drug release had a remarkable dependence on the crosslinking density of the microspheres, the highly crosslinked spheres releasing only around 35% of the incorporated steroid in 40 days compared to 70% from spheres lightly crosslinked. Determination of the in vivo bioavailability of the steroid from microsphere formulation by intramuscular injection in rabbits showed that a plasma concentration of 1 to 2 ng/ml was maintained up to 5 months without a high 'burst effect'. Data obtained suggest that the crosslinked chitosan microspheres would be an interesting system for long term delivery of steroids, (C) 1998 Elsevier Science B.V.Drug Delivery