Safety of intravitreal linezolid injection: electroretinographic and histopathologic studies in rabbits

Abstract

Objective: This study evaluated the safety of linezolid as an alternative intravitreal drug for the treatment of bacterial endophthalmitis.

Methods: Eight albino rabbits were divided randomly into 2 equal groups: the right eyes were injected intravitreally with linezolid (100 mcg/0.10mL in Group 1 and 200 mcg/0.10mL in Group 2) and the left eyes were injected with 0.10mL balanced salt solution. Indirect ophthalmoscopy before and after intravitreal injections determined the presence of any precipitates in the vitreous. Electroretinography (ERG) and histopathology evaluated the effects in the retina.

Results: No vitreous precipitates were found in all groups. Scotopic ERG showed a decrease in b-wave amplitude (p < 0.05) in Group 2 between 3 hours and 2 days and between 3 hours and 7 days after injection. Histopathology showed minimal inflammatory cells (<3 cells/hpf) in Group 2 and controls, trace vacuolizations in the ganglion-cell layer and partial loss of photoreceptor outer segment in Group 1 and in controls, and minimal decrease in the outer-nuclear-cell density in all groups.

Conclusion: Intravitreal injection of up to 200 mcg linezolid is safe and well tolerated in rabbit eyes and may be used in the treatment of human bacterial endophthalmitis following further studies.