In animal health care, current therapeutic regimens for severe external infections require repeated instillations of antibiotic eye drop solutions. The aim of this work is to drastically decrease the frequency of instillations by developing a long-acting ophthalmic insert. Ophthalmic inserts based on mixtures of hydroxypropyl cellulose, ethyl cellulose, poly(acrylic) acid and 25.0% (w/w) of gentamicin sulfate either combined with cellulose acetate phthalate or not were prepared using a specially designed ram extruder. The content of each component was optimized by evaluating tolerance and drug release in rabbits. Preliminary in vivo assays in rabbits led to a formulation with the favourable characteristics needed. These inserts were tested in dogs for drug release and compared with a commercial sold collyrium. The results shows that the inserts ensure effective gentamicin levels over 72 h with variation coefficients between 2 and 10%. These results are compared with those obtained with the eye drop solution (0.3%), which provides effective concentrations lasting less than 15 min with variation coefficients ranging from 63-96%. These soluble Bioadhesive Ophthalmic Drug Inserts (BODI) can be considered as a promising new ophthalmic delivery concept specifically designed for animal health care.