Emulsion polymeric drug carriers

New sustained technologies are also gaining much interest in ocular delivery, as in other routes. Liposomes as drug carriers have achieved enhanced ocular delivery of certain drugs, antibiotics, and peptides. Prolonged delivery of pilocarpine can be achieved with a polymeric dispersion or submicrometer emulsions [79]. 

The poly(alkylcyanoacrylate) nanospheres, widely used as drug carriers, are prepared by emulsion polymerization according to a method initially introduced by Couvreur et al. The monomers (isobutylcyano-acrylate, isohexylcyanoacrylate, n-butylcyanoacrylate) are dispersed in a continuous acidified aqueous phase under magnetic agitation. The anionic polymerization... 

FIGURE 54.24 Illustration of preparation for microgels of PEO-fc-PPO-fc-PEO via inverse emulsion polymerization. (Reprinted with permission from Langmuir, 21(6), Missirlis, D., Tirelli, N., and Hubbell, J.A., Amphiphilic hydrogel nanoparticles. Preparation, characterization, and preliminary assessment as new colloidal drug carriers, 2605. Copyright 2005 American Chemical Society.)... 

Drug loading in the polymeric nanocarriers is generally achieved by a method requiring the use of organic solvent to dissolve the drug, dialysis, oU-in-water emulsion solvent evaporation, and solid dispersion. Dmg incorporation can modify various physicochemical parameters of the carrier like size or surface charge. 

Pilocarpine is a drug commonly used in glaucoma therapy to relieve intraocular pressure (lOP), which is a cause of great discomfort to the patient. Piloplex is a sustained-release product based on an emulsion system of pilocarpine bound to a polymeric carrier [87,88]. Piloplex was shown to prolong a reduction in lOP as compared to standard pilocarpine hydrochloride drops. This is attributed to its bioadhesive properties, which keep the drug in the precorneal area longer than do conventional ocular dosage forms. 

High expectations were connected with this novel drug delivery system in the assumption that solid lipid nanoparticles may just combine the advantages of colloidal fat emulsions (biocompatibility, ease of preparation, avoidance of the use of organic solvents) and those of e.g. polymeric nanoparticles (solid state of the matrix). Due to the solid state of the nanoparticles, a sustained or even controlled drug release was expected. Over the years, SLN attained more and more interest in the scientific community all over the world as documented in the considerable number of research papers, review articles and book chapters in this field [e.g. Refs. 27-29]. Recently, a special issue oi Advanced Drug Delivery Reviews, Volume 59,2007 focused on this carrier system. 

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