Topical moxifloxacin efficacious in preventing endophthalmitis after intravitreal injection

Key Points

Fort Lauderdale, FL-Results of testing in an animal model demonstrated that topical moxifloxacin 0.5% ophthalmic solution (Vigamox, Alcon Laboratories) provided effective prophylaxis against endophthalmitis following an intravitreal injection, as reported by researchers from the University of Pittsburgh at the annual meeting of the Association for Research in Vision and Ophthalmology.

Regis P. Kowalski, MS, [M]ASCP, and colleagues presented findings from an experimental model that they developed of intravitreal injection-induced bacterial endophthalmitis. In a randomized controlled trial, they showed that endophthalmitis did not develop in any animals after intravitreal triamcinolone injection when they received topical moxifloxacin treatment pre- and postinjection. Clinical signs of endophthalmitis developed in 60% of control animals treated with topical saline.

"An increasing number of patients are being treated with intravitreal injections of triamcinolone and anti-vascular endothelial growth factor agents. Some treatments are being administered as often as once every month. The risk of postinjection endophthalmitis associated with such a high frequency of treatment is a major concern of retinal specialists," said Kowalski, associate professor of ophthalmology, University of Pittsburgh, and associate director of the university's Charles T. Campbell Ophthalmic Microbiology Laboratory.

The endophthalmitis model developed involved delivery of the intravitreal injection through a depot of Staphylococcus aureus (10⁷ colony-forming units) placed subconjunctivally 1 hour prior to the intravitreal injection. Animals treated with moxifloxacin received five doses administered every 15 minutes before the intravitreal injection and then were treated four times a day for up to 72 hours. The controls received saline drops with the same dosing frequency. The dose of triamcinolone administered was 4 mg/0.1 ml.

Diagnosis of endophthalmitis was based on clinical assessments and a confirmatory culture of a vitreous sample. Animals were examined daily, and the individual severity of 12 clinical signs of endophthalmitis was rated on a scale of 0 to 3. If clinical signs of endophthalmitis were observed, the animals were killed and a vitreous sample was drawn for culture. Animals in which clinical signs of endophthalmitis did not develop by 72 hours postinjection were killed, and a vitreous sample was taken from each.

Twenty animals were randomly assigned in equal numbers into the two treatment groups. In the moxifloxacin group, nine animals were able to be evaluated, and none developed endophthalmitis during the follow-up. That result compared with six of 10 evaluable control animals.

The median total clinical endophthalmitis score for the moxifloxacin group was 1.28 compared with 17.17 for the saline-treated controls. All vitreous samples from the moxifloxacin animals were negative for bacterial growth. The median colony count in the saline-treated animals was 1.55 × 10⁵ colony-forming units/ml. The differences between treatment groups in endophthalmitis incidence, clinical score, and bacterial colony count all were statistically significant.