Claudia Panfil

Semifluorinated alkanes as a liquid drug carrier system for topical ocular drug delivery.

Semifluorinated alkanes (SFA, e.g. perfluorobutylpentane F4H5, perfluorohexyloctane F6H8) are inert, non-toxic fluids capable of dissolving lipophilic drugs. The aim of this study to assess the bioavailability and safety of SFAs as drug solvents for the topical ocular application of Cyclosporin A (CsA). A commercially available CsA formulation (Restasis, 0.05% CsA in castor oil) was tested against two novel formulations of 0.05% CSA in (a) F4H5 containing Ethanol (0.5 w/w%) and (b) F6H8 containing Ethanol (0.5 w/w%) with 0.05% CsA. Formulations were tested on rabbit corneas cultured on an artificial anterior chamber with a constant flow of an aqueous humour supplement (Ex Vivo Eye Irritation Test (EVEIT) system). Anterior chamber fluids were sampled at multiple time points to analyse the CsA concentration following single and repeated application regimes by HPLC. Photographs of fluorescein sodium-stained corneas were recorded for corneal toxicity evaluation. The impact of the formulations on the integrity of the corneal barrier function was tested after drug application by fluorescein sodium corneal diffusion experiments. The influence on the corneal metabolism was evaluated by analysis of the metabolic markers glucose and lactate. Restasis did not pass the corneal barrier after short term application, CsA in ethanolic F4H6 reached a maximum of 152.95 ng/ml in anterior chamber fluid samples whilst CsA in ethanolic F6H8 reached a maximum of 15.12 ng/ml. After repeated applications for 8h, Restasis reached 21.07 ng/ml compared to 247.62 ng/ml and 174.5 ng/ml for F4H5 and F6H8, respectively. No corneal toxicity was observed in following application of any of the formulations. In contrast to the commercially available castor oil-based formulation, CsA dissolved in SFAs reached therapeutic inner ocular concentrations after topical administration, possibly leading to the replacement of systemic applications of CsA for inflammatory ocular disease.

Comparison of the lubricant eyedrops Optive®, Vismed Multi®, and Cationorm® on the corneal healing process in an ex vivo model

Purpose To evaluate the impact of lubricant eyedrops on the corneal healing process and corneal toxicity. Methods Optive® and Cationorm® were tested regarding corneal irritability against Vismed Multi® and 0.01% benzalkonium chloride as negative and positive control, respectively. Formulas were applied on rabbit corneas (n = 5) cultured on artificial anterior chambers (EVEIT system) hourly over 3 days. Initially, 4 corneal abrasions (2–5.4 mm2) were induced. All defects were monitored during drug application by fluorescein stains and photographs. To ensure corneal vitality, glucose and lactate concentrations were determined photometrically in artificial anterior chamber fluids. Corneal fluorescein sodium permeability was tested as an indicator of the corneal barrier function. Results Optive® and Vismed Multi® showed a complete corneal healing on day 2. In one cornea (Optive®), erosion reoccurred on day 3. Erosion sizes of Cationorm®-treated corneas increased significantly from 12.20 mm2 to a subtotal erosion of 51.89 mm2 on day 3. Histology revealed epithelial loss and severe alterations of the superficial stroma for Cationorm®. Glucose and lactate concentrations did not change after application of Optive® and Vismed Multi®. In contrast, Cationorm®- and BAC-treated corneas showed a significant increase in lactate concentrations. Conclusions Vismed Multi® application resulted in rapid corneal healing. Whether the toxicity seen for Optive® in one cornea is a valid result should be examined further. Cationorm® showed considerable corneal toxicity that could be caused by its additive, cetalkonium chloride. Otherwise, the electrostatic properties of Cationorm® led to a drug film on the area of epithelial loss that could hinder epithelial cell migration and adhesion in order to heal the lesion.

Comparison of the effects of various lubricant eye drops on the in vitro rabbit corneal healing and toxicity

Ingredients of lubricant eye drops are potentially harmful to the ocular surface. The products Optive, Optive Fusion, Neopt were tested regarding corneal irritability versus Vismed Multi and 0.01% benzalkonium chloride as negative and positive control, respectively. Formulas (30-40μl per hour) were applied hourly in-vitro for six days on rabbit corneas (n=5, per product) cultured in artificial anterior chambers (EVEIT system). Initially, four corneal abrasions (2.4-4.6mm2) were induced. All defects were monitored during drop application by fluorescein stains and photographs. To ensure corneal vitality, glucose and lactate concentrations in artificial anterior chamber fluids were determined photometrically. All products showed a complete corneal healing on day 2. Thereafter, all five Optive-treated corneas developed progressive fluorescein-positive epithelial lesions until day six (24.96μm, ±21.45μm, p<0.01). For Optive Fusion three corneas showed corneal erosions on day six (23.11μm, ±37.02μm, p>0.5) while Vismed Multi did not adversely affect the corneal integrity. Glucose/lactate concentrations remained unchanged while lubricants were applied. Histology revealed epithelial loss and severe alterations of the superficial stroma for Optive. Optive Fusion displayed a comparable pathology. Neopt did not significantly affect the corneal healing and integrity. This study suggested a cumulative corneal toxicity of Optive and, to a lesser extent, Optive Fusion most likely caused by its oxidative preservative, SOC. Clinical data are needed to clarify the application frequency at which corneal toxicity might occur. Neopt and Vismed Multi did not affect the corneal integrity.

Osmolarity of prevalent eye drops, side effects, and therapeutic approaches.

Purpose: Little is known about how the osmolarity of ophthalmic formulations affects the ocular surface. Because hyperosmolar eye drops could be therapeutic for treating corneal edema, this article presents an ex vivo model of corneal edema for testing ophthalmic drugs based on their osmolarity. The respective osmolarity of common eye drops found in the German market is also analyzed here. Methods: For modeling corneal edema, an Ex Vivo Eye Irritation Test was used to simulate an ocular anterior chamber with a physiological corneal barrier. To induce corneal edema, the anterior chamber was supplied with a hypoosmolar medium (148 mOsm/L) for 24 hours. Preserved and preservative-free 5% sodium chloride (hyperosmolar Omnisorb and Ocusalin 5% UD) were used for 1 hour, on 5 corneas each, to test their efficiency to reduce corneal edema in this model. Corneal thickness was determined by optical coherence tomography. Osmolarity of 87 common eye drops was measured by freezing point osmometry. Results: Ex vivo, the tested hypoosmolar condition induced corneal edema from 450 &mgr;m (±50 &mgr;m) at baseline to 851 &mgr;m (±94 &mgr;m, P < 0.0001). Omnisorb and Ocusalin 5% UD significantly reduced the corneal thickness by 279 &mgr;m (±28 &mgr;m, P < 0.001) for Omnisorb and 258 &mgr;m (±29 &mgr;m, P < 0.001) for Ocusalin 5% UD. Forty-three (49%) of the tested products had an osmolarity below and 44 (51%) above the physiological tear osmolarity of 289 mOsm/L. Osmolarity values of less than 200 mOsm/L were found in lubricant drops. The highest osmolarity was detected in Omnisorb (1955 mOsm/L). Conclusions: The Ex Vivo Eye Irritation Test has proven to be a reliable novel model of corneal edema for evaluating osmotic eye drops. Osmolarity measurements revealed a wide range from hypotonic to hypertonic formulations for commonly marketed ophthalmic drugs.

The Ex vivo Eye Irritation Test (EVEIT) model as a mean of improving venom ophthalmia understanding

&NA; Snakes belonging to the genus Naja (Elapid family), also known as “spitting cobras”, can spit venom towards the eyes of the predator as a defensive strategy, causing painful and potentially blinding ocular envenoming. Venom ophthalmia is characterized by pain, hyperemia, blepharitis, blepharospasm and corneal erosions. Elapid venom ophthalmia is not well documented and no specific treatment exists. Furthermore, accidental ejection of venom by non‐spitting vipers, as Bothrops, also occurs. The Ex vivo Eye Irritation Test model (EVEIT) has enabled important progress in the knowledge of chemical ocular burns. Considering the lack of experimental animal model, we adapted the EVEIT to study venom ophthalmia mechanisms. Ex vivo rabbit corneas were exposed to venoms from spitting (Naja mossambica, Naja nigricollis) and non‐spitting (Naja naja, Bothrops jararaca and Bothrops lanceolatus) snakes, and rinsed or not with water. The corneal thickness and the depth of damage were assessed using high‐resolution optical coherence tomography (HR‐OCT) imaging and histological analysis. All Naja venoms induced significant corneal edema, collagen structure disorganization and epithelial necrosis. Corneas envenomed by African N. mossambica and N. nigricollis venoms were completely opaque. Opacification was not observed in corneas treated with venoms from non‐spitting snakes, such as the Asian cobra, N. naja, and the vipers, B. jararaca and B. lanceolatus. Moreover, Bothrops venoms were able to damage the epithelium and cause collagen structure disorganization, but not edema. Immediate water rinsing improved corneal status, though damage and edema could still be observed. In conclusion, the present study shows that the EVEIT model was successfully adapted to set a new experimental ex vivo animal model of ophthalmia, caused by snake venoms, which will enable to explore new therapies for venom ophthalmia. HighlightsEx vivo Eye Irritation Test (EVEIT) was successfully adapted to set a new ex vivo animal model of snake venom ophthalmia.The EVEIT model reproduces the corneal opacification observed in case of African Elapid venom ophthalmia.Improvement of the corneal status, after envenomation, could be achieved by immediate water decontamination.