Preparation, characterization, and in vivo evaluation of triamcinolone acetonide microspheres after intravitreal administration

Abstract Purpose: The aim of this study was to evaluate the intraocular pressure (IOP) increasing effect and bioavailability of triamcinolone acetonide (TA) microspheres, as a novel drug delivery system, after intravitreal administration. Methods: Microspheres loaded by TA were prepared by the solvent evaporation method. After encapsulation, the final microspherical formulation was tested in an animal model. The left eyes of rabbits received microspherical TA and the right eyes were injected with conventional TA suspension. The drug concentration in the vitreous samples at days 7, 14, 28, and 56 after the injection was determined by high-performance liquid chromatography. The IOP was also checked at the same days with the Schiotz tonometer. Results: There was no statistically significant (P>0.05) difference between mean concentration of TA in the vitreous of right and left eyes at the different sampling times except day 56. Mean IOP of eyes that received microspherical TA was increased less than that of the eyes injected with TA suspension, and the difference was statistically significant (P<0.05) for each measurement day. TA was detectable in both eyes after 8 weeks. Both TA microsphere and suspension showed the sustained release profile. Conclusion: The results of this study showed less IOP increasing effect of triamcinolone microspheres in comparison with suspension form.