Colloidal Carriers for Ophthalmic Drug Delivery

Abstract

To achieve effective drug concentration at the intended site for a sufficient period of time is a requisite desired for many drug formulations. For drugs intended to ocular delivery, its poor bioavailability is due to pre-corneal factors. Most ocular diseases are treated by topical drug application in the form of solution, suspension and ointment. However, such dosage forms are no longer sufficient to combat some ocular diseases. Intravitreal drug injection is the current therapy for disorders in posterior segment. The procedure is associated with a high risk of complications, particularly when frequent, repeated injections are required. Thus, sustained-release technologies are being proposed, and the benefits of using colloidal carriers in intravitreal injections are currently under investigation for posterior drug delivery. This review will discuss recent progress and specific development issues relating to colloidal drug delivery systems, such as liposomes, niosomes, nanoparticles, and microemulsions in ocular drug delivery.

Solid lipid nanoparticles for ocular drug delivery

“…For instance, timolol and other intra-ocular pressure reducing agents can cause cardiac and vascular complications, especially if the patient is susceptible (Attama et al, 2009). Other pre-corneal factors limiting ocular drug absorption are drainage of the instilled solution, tear production (induced lachrymation), drug metabolism, and normal tear turn-over (Mainardes et al, 2005). The human cul-de-sac can usually accommodate ∼ 30 μL of fluids, whereas the instilled volume from eye drops is ∼ 50 μL (Mainardes et al, 2005).…”

“…Other pre-corneal factors limiting ocular drug absorption are drainage of the instilled solution, tear production (induced lachrymation), drug metabolism, and normal tear turn-over (Mainardes et al, 2005). The human cul-de-sac can usually accommodate ∼ 30 μL of fluids, whereas the instilled volume from eye drops is ∼ 50 μL (Mainardes et al, 2005). Therefore, large volumes of the medicament are lost through spillage from the cul-de-sac.…”

“…The cornea is a multilayered tissue consisting of the epithelium, the endothelium, and the stroma. The epithelial layer is lipophilic and consists of tight junctions that limit the entry of hydrophilic drugs and macromolecules into the cornea and the aqueous humor (Seal et al, 1998;Mainardes et al, 2005). This barrier can be breached by an epithelial defect or by subconjunctival injection.…”

“…Another drawback is the faster release rates associated with nanoparticles when compared to microspheres (Janoria et al, 2007). Physicochemical properties such as particle size, surface net charge, shape, solubility, degree of ionization, and lipophilicity influence drug ocular absorption and determine the route of administration (Mainardes et al, 2005). These factors can be tailored using novel nanoparticulate drug delivery systems that enhance the ocular bioavailability of drugs.…”

Enhanced antitumor activity of realgar mediated by milling it to nanosize

“…12 However, it has been suggested that a particlesize reduction might significantly accelerate its rate and extent of absorption. 13 Transforming poorly water-soluble drugs into nanosize crystals will dramatically enhance their bioavailability and extend their clinical use.…”