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Pharmacology: Pharmacodynamics: VISLUBE contains sodium hyaluronate, a natural polymer, which is also present in the structures of the human eye. The particular physical characteristics of sodium hyaluronate confer to VISLUBE its viscoelastic, mucomimetic and water retaining properties. In clinical studies, VISLUBE was shown to stabilize the tear film and increase the tear film break-up time (tear film BUT). This resulted in a reduction in the subjective ocular symptoms of burning, photophobia, pain and foreign body sensations and objective signs including tear film BUT, tear volume and staining with Rose Bengal and fluorescein together with an improvement in patient comfort and well being. The hypotonic formulation of VISLUBE also enhanced the treatment effect of VISLUBE in dry eye patients by compensation of the hypertonicity of tears in these patients. Tear hyperosmolarity, a core mechanism of dry eye disease, stimulates inflammatory cascade and cell apoptosis leading to ocular surface damage. Thus hypotonic eye drops would be a reasonable alternative for dry eye treatment. Evidence from many studies showed that treatment with hypotonic eye drops (150 mOsm/l) providing better results in improving signs and symptoms of dry eye disease compared to isotonic eye drops (300 mOsm/l).
VISLUBE also showed a marked reduction in the expression of the CD44 protective marker, the hyaluronic acid receptor which is over-expressed in inflammatory diseases, and increased the expression of protective markers such as mucus and goblet cells, CD63 and UIC2. It also reduced the expression of other inflammatory markers such as human leucocyte antigen-DR (HLA-DR) and cluster differentiation CD40 and caused a decrease in the expression of apoptosis markers such as Fas and Apo2.7. Sodium hyaluronate can also reduce toxic effect from Benzalkonium Chloride (BAK) on the ocular surface by neutralizing the cationic charge of BAK, entrapping BAK molecule into its sponge-like structure, and forming a cytoprotective coat on cell membrane. Moreover, sodium hyaluronate can stimulate corneal epithelial cell migration and proliferation leading to rapid corneal wound healing. The results from many studies showed the ability of sodium hyaluronate to increase healing rate, reduce wound area and improve ocular surface damage. Thus, this would explain the protective, anti-inflammatory, the BAK toxicity reducing, and wound healing effects of VISLUBE.
Pharmacokinetics: Due to its high molecular weight, sodium hyaluronate is not expected to pass through the conjunctiva and the corneal epithelium. Following intraocular administration of sodium hyaluronate, the t½ for elimination of the product from the aqueous humour was around 10.5 h and no product was detected 24 h after administration. After parenteral administration of sodium hyaluronate, this molecule is efficiently metabolized in the liver (t½=2.5 to 5.5 min).
