Delivery of drugs to the posterior segment of the eye is notoriously difficult and unfortunately many chronic conditions of the posterior segment often lead to sight-loss if not treated effectively. Current methods of delivery such as topical drops result in poor bioavailability at the back of the eye, while the blood brain retina imposes restrictions on the entry on drugs into the eye delivered by the systemic system. The gold-standard method for delivery of therapeutic concentrations of drugs is intravitreal delivery, which involves an injection into the vitreous cavity. Although this provides therapeutic levels of drugs, numerous injections are required to maintain these concentrations, and the frequency of injection can cause various adverse effects such as retinal detachment, vitreous haemorrhage and endophthalmitis. The present study investigates the potential use of solvent-induced in situ forming implants (ISFI) as a method of delivering drugs in a prolonged manner to the posterior segment of the eye. These systems are composed of a water-insoluble polymer dissolved in an organic solvent. Their low viscosity allows for easy administration through small-bore needles (e.g. 27 gauge) and on contact with an aqueous environment, such as the vitreous humour, phase inversion through solvent exchange takes place resulting in a biodegradable polymeric implant that can release drugs for an extended period. . As another method to improve posterior drug delivery in a minimally-invasive manner, microneedles (MN) were used to inject small amounts of ISFI formulation into sclera. Drug release and permeation stUdies across sclera indicated that the use of MN did indeed improve scleral permeation, with potential to allow posterior drug delivery from an intrascleral depot. From investigations carried out in the present study, ISFI show promise in transforming drug delivery to the eye and therefore possibly preventing the loss of sight in numerous individuals.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:678216 |
| Date | January 2015 |
| Creators | McMillan, Hannah Louise |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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