Ocular Delivery

The use of polymeric nanoparticles can prolong the retention time of drugs in the eye [70]. Despite these clear reports in the literature, no nanoparticulate products are on the market according to our knowledge. There are two reasons for this from our point of view. First, the profits from ocular products are relatively low; a company is therefore reluctant to replace an existing selling product by a completely new development. In case the product sells well anyway, why should there be an improved development causing relatively high costs not fully compensated by additional profit? In addition, the use of polymeric nanoparticles would require extensive toxicity studies, too expensive for a small-sale volume product such as eye formulations.

The incorporation of a drug into SLNs and application as SLN dispersion to the eye can clearly enhance the retention time [71]. Recently, the first investigations of SLNs for ocular delivery were published [72]. Due to the excellent tol-erability of lipids used for lipid nanoparticle production, for their topical application, only very limited toxicity studies are expected to be required (especially when using excipients accepted for topical use). Drainage to the nasal tract should also be no problem; many surfactants and lipids used in SLNs are also registered for nasal creams. NLCs could also be used for these formulations, again having the advantage of higher drug loads and more flexible modulation in drug release.

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