Safety and pharmokinetics of triamcinolone hexacetonide in rabbit eyes.

PURPOSE: The aim of this study was to evaluate whether intravitreal triamcinolone hexacetonide (TH) is a safe, longer lasting alternative to intravitreal triamcinolone acetonide (TA) in the rabbit eye. METHODS: Three groups, each comprising of 15 Dutch-belted rabbits, received a unilateral injection of 0.1 mL of drug and 0.1 mL of physiologic salt solution in the fellow eye. Group I received TA, group II received commercially available TH, and group III received reformulated iso-osmolar triamcinolone hexacetonide (rTH). Simultaneous bilateral dark-adapted electroretinography was performed following the injection. Retinal morphology was assessed by using histopathology in each group enucleated 12 weeks after injection. High-performance liquid chromatography of vitreous isolated from the enucleated eyes was used to determine drug concentrations. RESULTS: A significant reduction in saturated a-wave and maximal scotopic b-wave was observed in the group II eyes relative to the fellow control eyes at both 2 and 12 weeks postinjection (P < 0.001 for each comparison) but not in the other groups. Histopathology showed no differences between drug-injected eyes and fellow control eyes in groups I and III, but in group II there was severe degeneration of all retina layers. In group I, the drug half-life was 17.7 +/- 1.7 days, group II 44 +/- 13 days, and group III 12.8 +/- 2.3 days. CONCLUSIONS: The half-life of commercially available TH in the vitreous is double that of TA, but the former is toxic to the retina in this rabbit model. Reformulated iso-osmolar TH showed no evidence of deleterious effects to retina function or structure but had a similar half-life to TA.

Inhibition of experimental corneal neovascularisation by bevacizumab (Avastin).

AIM: To evaluate the effect of topically administered bevacizumab (Avastin) on experimental corneal neovascularisation in rats. METHODS: Silver nitrate sticks (75% silver nitrate, 25% potassium nitrate) were used to perform chemical cauterisation on the corneas of 16 eyes from 16 male Long Evans rats. For the following 7 days, the 10 eyes in the treatment group were instilled with bevacizumab 4 mg/ml drops twice daily, whereas the 6 eyes in the control group received placebo (normal saline drops twice daily). Digital photographs of the cornea were analysed to determine the area of cornea covered by neovascularisation as a percentage of the total corneal area. RESULTS: In the bevacizumab-treated eyes, neovascularisation covered, on average, 38.2% (15.5%) (mean (SD)) of the corneal surface compared with 63.5% (5.0%) in the control group (p<0.02, Mann-Whitney U test). CONCLUSION: Topically administered bevacizumab (Avastin) at a concentration of 4 mg/ml limits corneal neovascularisation following chemical injury in the male Long Evans rat model.

Toxicity of high-dose intravitreal adalimumab (Humira) in the rabbit.

PURPOSE: To evaluate the ocular toxicity of escalating doses of intravitreous adalimumab (Humira®) in the rabbit eye. METHODS: Thirty New Zealand albino rabbits received intravitreous injections of 0.5 mg (6 eyes), 1.0 mg (6 eyes), 2.5 mg (6 eyes), 5 mg (6 eyes), and 10 mg (6 eyes) adalimumab. Slit lamp biomicroscopy and fundoscopy were carried out at baseline, day 7, and day 14 after intravitreous injection, whereas electroretinography (ERG) was carried out at baseline and day 14. Animals were euthanized on day 14, and histopathological examination of the eyes was performed. RESULTS: Slit lamp biomicroscopy and fundoscopy were normal in all eyes receiving doses up to 5 mg. In the 10 mg group, 3 of 6 eyes showed mild anterior chamber inflammatory reaction on day 7. Similarly, scotopic and photopic a- and b-wave ERG amplitudes at baseline and day 14 were similar in all groups up to 5 mg, but there was a significant decrease in the photopic-wave ERG response in the 10 mg group (P=0.046). Finally, histopathology demonstrated no differences among eyes receiving balanced salt solution, 0.5, 1.0, 2.5, 5.0, or 10 mg of adalimumab. CONCLUSIONS: Intravitreous adalimumab exhibited no associated ocular short-term toxicity in rabbit eyes up to the 5 mg dose. In the 10 mg group mild clinical findings and ERG amplitude reduction could reflect early toxicity.

Ocular toxicity of intravitreous adalimumab (Humira) in the rabbit.

PURPOSE: To evaluate the ocular toxicity of escalating doses of intravitreous adalimumab (Humira) in the rabbit eye. METHODS: Twelve New Zealand albino rabbits received unilateral intravitreous injections of 0.1 ml of adalimumab 0.25 mg (three eyes), 0.50 mg (three eyes), 1.0 mg (three eyes) or 0.1 ml balanced salt solution (BSS, three eyes). Slit-lamp biomicroscopy and fundoscopy were carried out at baseline, day 1, 7 and 14 following intravitreous injection, while electroretinography (ERG) was carried out at baseline and day 14. Animals were euthanized on day 14, and histopathological examination of the eyes was performed. RESULTS: Slit-lamp biomicroscopy and fundoscopy were normal in eyes having received BSS, 0.25 mg or 0.50 mg adalimumab; however, inflammation was present in two of three eyes having received 1.0 mg adalimumab. Similarly, comparison of scotopic and photopic ERG light at baseline and day 14 demonstrated no changes in eyes receiving BSS, 0.25 mg or 0.50 mg adalimumab, but two of three eyes having received 1.0 mg adalimumab showed a greater than 30% reduction in a and b wave. Finally, histopathology demonstrated no differences between eyes receiving BSS, 0.25 mg or 0.50 mg of adalimumab, but two of three eyes injected with 1.0 mg demonstrated inflammatory cell infiltration of the vitreous and anterior chamber, with one of these eyes demonstrating retinal necrosis. CONCLUSIONS: Escalating doses of intravitreous adalimumab in rabbit eyes caused no detectable functional or structural ocular toxicity up to a dose of 0.50 mg. Administration of 1.0 mg in 0.1 ml was associated with an inflammatory reaction and retinal necrosis.

Etanercept monotherapy induces complete resolution of cystoid macular edema in a patient with intermediate uveitis.

BACKGROUND: There is controversy on whether etanercept, an anti-tissue necrosis factor agent, shares infliximab's purported efficacy in the treatment of intermediate uveitis and, in particular, intermediate uveitis-associated cystoid macular edema. METHODS: Interventional case report. RESULTS: A 29-year-old patient with decreased vision bilaterally secondary to cystoid macular edema complicating chronic idiopathic intermediate uveitis refractory to oral corticosteroids, methotrexate (17.5 mg weekly), and cyclosporine (100 mg daily) started etanercept monotherapy with rapid and complete resolution of cystoid macular edema and dramatic improvement in visual acuity. CONCLUSION: Etanercept may have a role in the treatment of refractory intermediate uveitis and intermediate uveitis-associated cystoid macular edema.

Testing intravitreal toxicity of bevacizumab (Avastin).

PURPOSE: To evaluate the retinal toxicity of varying doses of bevacizumab when injected intravitreally in rabbits. Bevacizumab has been approved by the US Food and Drug Administration for the treatment of metastatic colorectal cancer. MATERIALS AND METHODS: Twelve New Zealand albino rabbits were used for this study and divided into four groups. Four concentrations of bevacizumab were prepared: 500 microg/0.1 mL, 1.0 mg/0.1 mL, 2.5 mg/0.1 mL, and 5.0 mg/0.2 mL. Each concentration was injected intravitreally in one eye of each of three rabbits; 0.1 mL volume of sterile balanced saline solution was injected into the contralateral eyes. Slit-lamp and funduscopic examinations were performed and the animals were observed for 2 weeks for signs of infection, inflammation, or toxicity. A baseline electroretinogram (ERG) was performed before the drug treatment and at day 14 before the animals were killed. The enucleated eyes were prepared for histologic evaluation of retinal toxicity. RESULTS: Histologic and ERG results in all groups showed no retinal toxicity. However, some inflammatory cells were found in the vitreous at the 5-mg dose. CONCLUSIONS: Intravitreal bevacizumab did not appear toxic to the retina in albino rabbits at a concentration of 2.5 mg. Intravitreally injected bevacizumab should be evaluated for efficacy in choroidal neovascularization and macular edema.