Methazolamide calcium phosphate nanoparticles in an ocular delivery system.

A new system for the local delivery of methazolamide to the eye has been developed based on calcium phosphate (CaP) nanoparticles. The methazolamide loaded CaP nanoparticles were prepared through the formation of an inorganic core of CaP and further adsorption of the methazolamide. The maximum loading of methazolamide studied using UV-vis spectrophotometry was about 0.2% (w/w). The drug-loaded particles had a negative surface charge at about -30 mV while their mean particle diameter was estimated to be 256.4 nm. In vitro release studies demonstrated diffusion-controlled release of methazolamide from the CaP nanoparticles over a period of 4 h. In vivo studies indicated that the intraocular pressure (IOP)-lowering effect of the inorganic nanoparticle eye drops lasted for 18 h, which was significantly better than the effect of 1% brinzolamide eye drops (6 h). Physical stability studies indicated that the preparation was stable for 6 months at 40 degrees C. These findings suggested that methazolamide bound to CaP nanoparticles might be useful in the local treatment of glaucoma.