nanocapsules emulsion h nanoparticles t �� microparticles fig indomethacin concentrations attained in the aqueous clindamycin phosphate vet humor following the topical application, in rabbits, of indomethacinloaded carriers and a control drug solution mean values � sd, n = , p clindamycin phosphate vet compared with indocollyre p compared with colloidal suspensions reprinted from ref , with permission from pharmaceutical press immunosuppressive peptide cyclosporin a interestingly, following topical administration of pecl nanocapsules containing cyclosporin a, we observed corneal levels of the drug which were five times higher than those provided clindamycin phosphate vet by an oily solution topical formulation of cyclosporin clindamycin phosphate vet typically used these high levels were not, however, translated into high drug concentrations in the aqueous humor a result that was attributed to the important hydrophobicity of this peptide and its tendency to associate with lypophylic components therefore, at present, there is a proofofconcept of the efficacy of polyester nanocapsules for enhancing clindamycin phosphate vet the concentration of topically applied drugs in the corneal epithelium whether this enhanced concentration may clindamycin phosphate vet or may not lead to a favored accumulation of the drug in the inner eye is expected to be largely dependent on the physicochemical characteristics of the drug polysaccharidebased nanoparticles the polyester polymers described above are hydrophobic polymers that need to be biodegraded into hydrophilic oligomers in order to be eliminated from the clindamycin phosphate vet body a very different class of polymers, which has only received attention in the last few years, is the one represented by the hydrophilic polysaccharides hyaluronic acid and chitosan are two types of polysaccharides which have opened new prospects in the ocular drug delivery area the choice of hyaluronic acid has been justified by its bioadhesive character, but also by its well known imitrex behavior safety profile in fact, hyaluronic acid is already being used as a clindamycin phosphate vet substitute for vitreous humor in intraocular surgery, since it constitutes a basic component of the vitreous body on the other hand, chitosan clindamycin phosphate vet is a polycationic biopolymer which exhibits several favorable biological properties for ocular drug administration these properties include mucoadhesiveness biodegradability in the rich lysozyme clindamycin phosphate vet containing mucus ie ocular mucosa, and also wound healing and antimicrobial activity despite the number clindamycin phosphate vet of articles showing the efficacy of hyaluronic acid solutions for improving the retention of drugs applied topically onto the eye, the only clindamycin phosphate vet particulate formulation that has been tested in vivo was composed of microparticles zm rather than nanoparticles these hyaluronate microparticles were shown to increase the residence time of the model drug methylprednisolone clindamycin phosphate vet at the ocular surface of the rabbit eye taking into account the reported influence of the size on the interaction of particles with the ocular mucosa, we have recently designed nanoparticles consisting of hyaluronic acid and chitosan at present, we know that these nanoparticles are stable upon incubation in simulated lachrymal fluids and in vivo studies are in progress in order to evaluate their mechanism of interaction with the ocular mucosa chitosan has also received significant attention in the ophthalmic field one of the chitosanbased systems that has exhibited an clindamycin phosphate vet interesting behavior following topical ocular administration, is the one consisting of chitosan nanoparticles these nanoparticles have been tested on the rabbit model clindamycin phosphate vet for their ability to enhance the concentration of cyclosporin a at the level of the ocular mucosa as expected, the results showed that clindamycin phosphate vet the chitosan nanoparticles were able to increase the concentrations of cyclosporin a in the external ocular tissues cornea and conjunctiva significantly for up to hr postinstillation fig despite this enhanced clindamycin phosphate vet retention of the drug in the external clindamycin phosphate vet tissues, the levels attained in the internal ocular structures ie aqueous humor, iris and ciliary body and in the blood were negligible consequently, these results suggested the utility of this new formulation for the treatment of surface eye diseases, ie dry eye or inflammatory diseases these high drug concentrations restricted to the periocular tissues were later explained by a high zocor and alcoho corneal and conjunctival surface retention of chitosan nanoparticles clindamycin phosphate vet indeed, in a study consisting of evaluating the concentration of fluorescent chitosan, either in the form of nanoparticles or as a solution, in cornea and conjunctiva, we could conclude that the affinity of chitosan for the ocular surface is greater when it is in a particulate form this conclusion invites interesting prospects with regard to the potential of chitosan nanoparticles clindamycin phosphate vet as drug carriers for topical ocular administration clindamycin phosphate vet keeping this in mind, we tested the acute clindamycin phosphate vet tolerance of chitosan nanoparticles following topical instillation to rabbits very recently the results gave evidence of an excellent tolerance, without any sign of irritation or damage of the ocular surface structures cya concentration in the cornea ng cyag cornea ?