Design of new formulations for topical ocular administration: polymeric nanocapsules containing metipranolol

To investigate the potential of polymeric nanocapsules for ocular delivery of beta-blockers, several formulations of polyisobutylcyanoacrylate and polyepsiloncaprolactone nanocapsules containing metipranolol base were developed. These formulations differed in the polymer forming the coating and in the type and volume of the oil encapsulated. Analysis of particle-size distribution, electrophoretic mobility, and loading efficiency of the nanocapsules revealed that the type of oil is the most important factor influencing these properties. From the in vitro release studies, we concluded that drug diffusion through a dialysis membrane is delayed as a consequence of the encapsulation process. However, the release profiles were not influenced by the polymeric coating, suggesting that drug release from these systems is governed mainly by the partition of the drug between the oily core and the aqueous release medium. Nevertheless, despite the inability of the polymer coat to control the release of the drug, its contribution to the stabilization of the emulsion was noted. Finally, the suitability of these formulations for ophthalmic administration was investigated. Although the pharmacologic response was not affected by the encapsulated metipranolol compared with the commercial eye drops, a drastic reduction of the drug's systemic side effects was observed.