Administering antibiotics through the cornea

The anatomic and physiologic structure of the eyes constitutes by itself an important barrier when administering medicine. The amount of medicine that passes through the cornea by applying creams or drops is very limited and it is necessary to develop alternative, more effective ways of administering them ocularly. Researchers at the Pharmacy Department of the CEU Cardenal Herrera University have published the design of a new bioadhesive ocular insert which is placed inside the eyelid and releases a larger amount of medicine through the cornea in a controlled way in the international journal Drug Delivery and Translational Research.

Specifically, researchers at the CEU UCH have developed this new insert for the ocular administration of the antibiotic moxifloxacin, which is applied in cases of bacterial infections of the eyes such as corneal queratitis or bacterial endophthalmitis. The Investigation Group for the Development of New Pharmaceutical Formulas at the CEU UCH, headed by the dean of the Health Sciences Faculty, Alicia López Castellano, undertook the research, a result of the doctoral thesis of María Sebastián Morelló, as well as teachers and researchers María Aracely Calatayud, Vicente Rodilla and Cristina Balaguer, who are coauthors.

Soluble insert instead of an injection

As the authors of the study explain, "when we apply cream or drops in the eyes, eyeball defense mechanisms such as tears are triggered, which dilutes the applied medicine. Sometimes, less than 5% of the medicine administered in this way manages to penetrate the eye in an effective way. Therefore, pharmaceutical research aims to develop ocular inserts, very thin cylinders or discs made of bioadhesive polymeric materials, which adapt to the shape of the eye and release the medicine through the cornea in a controlled manner."

Research performed at the CEU UCH has developed and analysed the efficiency of different types of inserts, using bioadhesive polymers with different physicochemical characteristics to compare them to discover which one could obtain the optimal degree of permeability to administer moxifloxacin. The research has made it possible to develop a very thin, practically transparent insert which is easily adhered to the ocular mucosa, providing larger concentrations of moxifloxacin through the cornea than other administration formats currently commercialised, such as orally.

According to the CEU UCH research team, "the ocular release of moxifloxacin with this insert would make for an improved treatment of some ocular illnesses such as bacterial endophthalmitis, an infection of the eyeball which can appear after suffering a wound or as a complication following intraocular surgery. It can also be used for treating corneal queratitis, an infection of the cornea which causes inflammation and can leave a leucoma or scar as a result. In both types of infection, vision can become severely compromised without the appropriate treatment."

Permeability of the corneal tissue

In order to establish the physicochemical properties of the most efficient bioadhesive polymers to be used as ocular inserts in order to administer said antibiotic, during research, the CEU UCH team has performed moxifloxacin diffusion ex vivo experiments through rabbit corneas preserved at different temperatures. The histological differences of these corneas have been studied to determine whether the use of those which have been frozen to study the absorption through this type of tissue can be used. According to the researchers, "the ocular diffusion studies we have undertaken reveal significant differences of diffusion through fresh and frozen corneas, which are very useful for the development of future research to test new ocular inserts."

The development of this ocular insert to administer moxifloxacin opens new treatment possibilities for ocular infections. A research line which the CEU UCH research team will continue to develop in future projects with other types of medicines.