Hydrogel lens for incorporation of Brimonidine Tartrate: a pre-formulation study

Abstract

Approximately 11.9 million people suffer from vision impairment or blindness due to glaucoma, a condition characterized by progressive optic nerve damage that primarily affects peripheral vision and can lead to blindness. The brimonidine tartrate (BRT) eye drops, a third-generation alpha-adrenergic agonist, are commonly used for glaucoma treatment, however present (i) side effects, (ii) low ocular availability (1-7%), (iii) nasolacrimal drainage and (iv) compliance issues that compromise its continuous use, leading to the therapeutic inefficacy. Then, new drug delivery systems, such as hydrogel contact lenses, may improve the patient compliance, and promote suitable ocular drug delivery. Based on this, the aim of this study was to produce and characterize brimonidine tartrate-loaded hydrogel lenses (BRTHL). The BRTHL was prepared by dissolving PVA at 90 ºC, followed by the addition of sodium hydroxide and sodium trimetaphosphate for crosslinking, followed by BRT incorporation during the manufacturing process. Posteriorly, the BRTHL was evaluated concerning the drug entrapment efficiency by UV-Vis spectrophotometry, in addition to light transmittance, thickness measurements, swelling behavior and Fourier transform infrared spectroscopy (FTIR). The BRTHL demonstrated an average drug entrapment efficiency of 72% ± 7.72%, which corresponds to 4.00 ± 0.35 µg/mg of hydrogel, a value similar to the commercial BRT eye drops. The BRTHL exhibited over 95% of transmittance, indicating adequate optical clarity. The thickness measurements were within optimal ranges for oxygen permeability and showed an average of 0.192 ± 0.010 mm. The swelling behavior of the hydrogels showed efficient water absorption, supporting potential drug release. The FTIR results indicated the success of the crosslink process. Then, the developed BRTHL exhibited suitable physical and chemical properties, effective drug loading, and satisfactory light transmittance. The obtained results demonstrate their potential for ocular use, paving the way to its further use as a novel drug delivery system for BRT