OCULAR DRUG-DELIVERY - A COMPARISON OF TRANSCORNEAL IONTOPHORESIS TO CORNEAL COLLAGEN SHIELDS

Topical administration of drugs to treat ocular disease is accomplishe d primarily by means of solutions, ointments, and suspensions. These a re relatively inefficient as drug delivery systems; often only 1% of t he available drug is absorbed by the eye. Two ocular drug delivery sys tems currently being studied are transcorneal iontophoresis and collag en shields. Transcorneal iontophoresis is intended to drive charged dr ugs by an electric current into the cornea. In a Pseudomonas model of bacterial keratitis, as well as in pharmacokinetic studies, ocular ion tophoresis of gentamicin, tobramycin, or ciprofloxacin was superior to topical ocular drops for reducing Pseudomonas in the cornea. Both ion tophoretic methods were shown to be safe and nontoxic to the rabbit co rneal epithelium. The collagen shield, designed to prolong drug contac t with the eye, is made from porcine scleral tissue that has been extr acted and molded into a contact lens configuration. The shields can ab sorb the equivalent of drug present in 1-2 drops of a topical aqueous solution. Chemotherapeutic studies in an experimental Pseudomonas kera titis model showed that collagen shields containing gentamicin, tobram ycin, or ciprofloxacin were equal to or better than frequent applicati ons of fortified antibiotic drops for significantly reducing the bacte ria in the cornea. The results gained from these experimental studies on corneal iontophoresis suggest the need for clinical trials.