The present study evaluates the in vitro release of diclofenac sodium (DFNa) from contact\nlenses based on poly-2-hydroxyethyl methacrylate (pHEMA) hydrogels containing an embedded\nmicroemulsion to extend release duration. The oil (ethyl butyrate)-in-water microemulsion systems are\nprepared with two non-ionic surfactants, Brij 97 or Tween 80, together with a long-alkyl chain cationic\nsurfactant, cetalkonium chloride (CKC).Without CKC, Brij 97 or Tween 80-based microemulsions\nshowed average droplet sizes of 12 nm and 18 nm, respectively. The addition of CKC decreased\nthe average droplet sizes to 2-5 nm for both non-ionic surfactants. Such significant reduction in\nthe average droplet size corresponds to an increase in the DFNa release duration as revealed by the\nin vitro experiments. Contact lens characterization showed that important properties such as optical\ntransparency and water content of Brij 97-based contact lenses with cationic microemulsions was\nexcellent. However, the optical transparency of the corresponding Tween 80 based contact lenses was\nunsatisfactory. The results indicate that cationic microemulsion-laden contact lenses can benefit from\ncombinatory effects of microemulsions and cationic surfactant at low CKC weight percentage, e.g.,\nwith the release of 70% of the drug in 45, 10, and 7 h for B97-CKC-0.45%, CKC-0.45%, and control\nlenses, respectively. However, the microemulsion effect on extending DFNa release became negligible\nat the highest CKC weight percentage (1.8%).
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