Development and characterization of prolonged release Timolol maleate cubosomal gel for ocular drug delivery

The main objective of ocular drug delivery is to improve the currently available conventional dosage form and exploit newer drug delivery system, with the view to improve their therapeutic efficiency. Topical application of eye drops is quite common among the patients suffered from the eye diseases. Commonly used conventional eye drops shows low ocular bioavailability due to constant lachrymal secretion, tear turnover, blinking, reflex and rapid nasolachrymal drainage. Normal drainage of an instilled dose commences immediately on instillation and is essentially completed within 5 min (Achouri et al., 2013). Typically less than 5% of ocular bioavailability is achieved for eye drops due to the short precorneal residence times. Consequently, there is a need for frequent instillation of concentrated solutions to achieve the desired therapeutic effect. To overcome these problems various ophthalmic formulations, such as viscous solutions, ointments, gels, nanoparticles or polymeric inserts have been investigated (Patel et al., 2013). The corneal contact time has been increased to varying degrees by these vehicles. But, they have not been unanimously accepted, because of blurred vision (e.g. ointments) or lack of patient compliance (e.g. inserts). As a result, good ocular bioavailability following topical delivery of a drug to the eye remains a challenge and yet to be resolved (Li et al., 2010).