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Research Says: Save Vision thru Antibiotic Inserts for Sick Cornea

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Goodbye creams and eye drops! Ocular inserts have come with a high absorbing rate of antibiotics around the cornea to effectively treat corneal keratitis, an infection of the cornea.

Valencia-based researchers at the CEU Cardenal Herrera University Pharmacy Department developed and published in the international journal Drug Delivery and Translational Research the design of new bioadhesive ocular insert which is much more effective than currents methods. The insert is placed in the inner eyelid and discharges a large amount of antibiotic moxifloxacin in a highly controlled manner.

Alicia López Castellano, dean of the CEU UCH Health Sciences Department, led the investigation team in the undertaking of the research. The said research built on the results of the doctoral thesis of María Sebastián Morelló and co-authors María Aracely Calatayud, Vicente Rodilla and Cristina Balaguer.

 

Eye Anatomy

CEU UCH researchers developed the ocular inserts to administer the antibiotic moxifloxacin applied to the infected eye caused by corneal keratitis or bacterial endophthalmitis, the infection of the eyeball.

Researchers explained that the anatomic and physiologic structure of the eyes is, by itself, a crucial barrier in the administration of the medicines. However, the amount of the medicine, say creams or drops that reach the cornea, is very limited. Thus, the research took this said limitation into consideration to pursue alternatives to address the necessity.

"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 percent 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," the research said.

The conjunctiva, when exposed to various ophthalmic medications will exhibit sensitive response because this mucous membrane is highly reactive.

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Soluble Inserts Methodology

The team developed and studied different types of inserts to test the efficiency. They analyzed a number of bioadhesive polymers with individualized physicochemical characteristics. The comparison led them to the conclusion that an optimal degree of permeability necessitated the administration of the moxifloxacin antibiotic.

The process arrived at the development of very thin, transparent, easily adherent insert for the ocular mucosa. The inserts were provided with large concentrations of antibiotic for the cornea. Something that has not been done before and proved effective in the treatment as compared to commercial creams, oral tablets or gels.

“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 keratitis, 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," researchers explained.

 

The Corneal Tissues of Rabbits

The research explained the process involved to establish physicochemical properties of bioadhesive polymers most effective to use ocular inserts.

During the experiment process, the film forming polymer, PVP and bioadhesive polymers, HPMC, CMC, and carbopol were prepared. The ocular inserts, film cast, and prepared films went through the investigations to evaluate using the criteria -- physical and mechanical properties, swelling behaviors, ex vivo bioadhesion, and in vitro drug release. The highly optimized formulation was tested and compared with other ocular anti-inflammatory piroxicam drops.  

The piroxicam formulation was converted into the bioadhesive ocular inserts aimed at sustaining the release of drugs, reducing the dose frequency, and enhancing ocular bioavailability.

The CEU UCH team diffused the moxifloxacin in an ex vivo experiment using rabbit corneas under various temperatures. Differences in histological components of corneas studied were found specifically absorption characteristics of fresh and frozen rabbit corneas.

"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 researchers explained.

In line with this development, the CEU UCH research team will pursue future projects with other types of medicines. The results on moxifloxacin paved possibilities of new treatment for ocular infections.

 

Antibiotic Resistance

The research team ensured that treatment must be active and potent in order to eliminate the pathogen, thereby, resist the possibility of developing antibiotic resistance. The resistance strains happen in the process of obtaining new genetic element that encourages the resistance. In antibiotics, the resistant strain survives by inhibiting competing non-resistant strains.

The resistance is often subdued by treatment of higher tissue levels however, it is unachievable with systemic application. On the other hand, the significant concern is the ophthalmic antibiotics below the required dosage by poor concentration, frequency of use, disregard of the medicine, and insufficient duration of therapy.

The topical ophthalmic drugs available today require dosage minimum of 4 times of application in a day to maintain the therapeutic tissue levels. Less and infrequent  dosage usually allows resistant strains to prevail and become a source of future ocular infections.

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