In vitro pharmaceutical characterization and statistical optimization of a novel topically applied instantly-soluble solid eye drop matrix

Ocular diseases of the anterior segment of the eye are increasing and the development of novel drug delivery systems for improved treatment is necessary. The aim of this study was therefore to design and evaluate an instantly-soluble solid eye drop (ISED) for topical ophthalmic drug delivery of the model drug timolol maleate. The porous nature of the lyophilized ISED resulted in rapid fluid ingression, immediate hydration, and dissolution of the ocular matrix. The ISED was lyophilized employing hydroxypropylcellulose and pluronic (R) F68 as the matrix forming polymers. Polyacrylic acid sodium enhanced the solubility of the ISED, di-glycine, an anti-collapsing agent, while maltodextrin improved the matrix resilience. A statistical design was employed for optimizing the texture, disintegration, and the mean dissolution time (MDT50%) of the ISED. Results revealed that a robust rapidly disintegrating ISED was produced with the fastest disintegration time recorded at 0.20 s and drug release between 79 and 96%. In addition, improved corneal drug permeation was observed compared to pure timolol dispersion. The maltodextrin concentration significantly affected the ISED matrix resilience (p = 0.007) and pluronic F68 had a greater impact on disintegration time (p = 0.000) and MDT (p = 0.000). The ISED formulation may be a promising alternative to the use of liquid eye drops for topical ophthalmic drug delivery.