Extended release of dexamethasone from oleogel based rods

Topical and systemic methods are not able to deliver ophthalmic drugs for treatment of retinal diseases. Consequently, invasive monthly intravitreal injections through the eyeball are required to deliver retinal drugs. A reduction in the frequency of the injection through extended release of the drugs could have significant clinical benefits.

Oleogels containing ethyl cellulose as the gelator at 10% (wt%) in soybean oil were loaded with dexamethasone above the solubility limit and expunged from a syringe to create cylindrical rods for extended drug delivery. The devices were imaged to explore particle distribution and drug release was measured under sink conditions in buffer. A model was developed and fitted to data to determine effective drug diffusivity.

Dexamethasone is released slowly due to the presence of the drug particles that serve as drug depots. The release increases from 600 to 3000 h as the drug loading is increased from 3% to 28%. The release profiles can be modeled by considering drug dissolution and diffusion, as well as the tortuosity of the matrix due to the presence of the voids formed after the drug particles have dissolved. The proposed approach is promising as the release profiles of the drug are comparable to commercial devices.