Reliability of intravitreal nepafenac in rabbits.

Purpose: The purpose of this experiment was to investigate the possible toxic effects of Nepafenac, a nonsteroidal anti-inflammatory molecule, after its intravitreal application in various concentrations.

Methods: Forty pigmented rabbits were randomly divided into 4 groups, each including 10 rabbits. The active ingredient Nepafenac was prepared to be applied in different doses, for intravitreal use. Under topical anesthesia, following pupil dilatation, 0.3, 0.5, 0.75, and 1.5 mg doses of Nepafenac was applied intravitreally into the right eye. In each rabbit, the right eye was considered to be the study group. Saline was injected intravitreally into the left eye of each rabbit, and these eyes were considered to be the control group. Immediately after the injection and at the 1st, 4th, and 8th weeks, fundus examination by indirect ophthalmoscopy and intraocular pressure measurement were conducted. Furthermore, electroretinographic (ERG) recordings were taken at the 4th and 8th weeks. At the end of the 8th week, eyes of the surviving 26 rabbits were enucleated, and then animals were sacrificed. Following necessary fixation procedures, histopathological investigations were conducted by using a light and electron microscope. In the histological cross sections, differences between the eyes with injection and the control group were evaluated, and total retinal thickness, inner nuclear layer thickness, and outer nuclear layer thickness were measured.

Results: No pathology was found by clinical examination of either group. In the photopic and scotopic full-field ERG, conducted before the injection and in the 4th and 8th weeks after the injection, no statistically significant difference was determined between the study group and the control group. In the histological evaluation of the preparations, there were no statistically significant differences in the retina thickness of control and study groups. In the electron microscopic examinations, there were no toxicity findings in the eyes with injection.

Conclusions: Our data show that intravitreal application of 0.3, 0.5, 0.75, and 1.5 mg doses of Nepafenac active substance is nontoxic to the rabbit retina.