Nasal preparations systemic absorption

Femandez-Urrusuno et al. (1999) investigated the potential of chitosan (MW <50,000-130,000 DD 70-87%) nanoparticles as a system for improving the systemic absorption of insulin following nasal instillation. Nanoparticles prepared by ionotropic gelation with tripolyphosphate... 

This chapter deals with preparations for nasal administration, with a local or a systemic effect. Classical nasal preparations were always associated with local ailments, but nowadays the interest in the nasal route for systemi-cally acting substances and direct nose to brain delivery is increasing. Fast absorption, the possibility of high blood levels and a patient friendly dosage form are the reasons. Nasal administration of medicines with local effect is the first choice for the treatment of topical nasal disorders. It is also an attractive route for low dose active substances with a systemic effect, such as peptides or benzodiazepines (e.g. midazolam). When compared to parenteral administration nasal administration is more easily applied and causes less risk of infection. 

Generally speaking active substances with a systemic therapeutic action can be formulated as nasal preparations under the following conditions high water-solubUity (required dose must fit in 25-150 microlitres vehicle), sufficient chemical stability, no unpleasant smell or taste, favourable nasal absorption parameters, minimal nasal irritation and clinically important properties such as fast onset of therapeutic action, low dosage (normally less than 25 mg per dose), and no toxic metabolites [3, 8]. 

Section 16.2.6 discusses biopharmaceutics of nasal preparations fi om a general biopharmaceutics viewpoint. This subsection adds some more specific details, first on the nasal absorption and then on the many investigations on absorption enhancing substances. The interest for nasal absorption is predominantly raised by the desire to find an alternative administration route for systemically acting active substances. 

Drug permeability, metabolism, and toxicity can be evaluated in vitro using models of the nasal epithelial in preparation for in vivo experiments. Human nasal epithelial cell cultures and animal nasal mucosa mounted in Ussing chambers provide convenient, simple systems in which drug targeting and absorption mechanisms can be investigated under defined, controlled conditions [45],... 

Eye medication is intended for local use on or into the eye. Eye drops and semisolid preparations are usually applied topically, in the lower conjunctival sac. Absorption of active substances into the ocular blood vessels and also into the systemic circulation occurs at the conjunctiva and nasal mucosae. Due to absorption, systemic side effects could appear after instillation. 

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