Brain uptake of an anti-ischemic agent by nasal administration of microparticles

N(6)-cyclopentyladenosine (CPA) has neuronal anti-ischemic properties, but it is not absorbed into the brain from the bloodstream, where it shows poor stability and induces side effects. Microparticulate drug delivery systems designed for CPA nasal administration and constituted by mannitol or chitosan, were prepared by spray-drying and characterized. Mannitol-lecithin microparticles showed high CPA dissolution rate, whereas chitosan microparticles controlled its release rate. In vitro mucoadhesion studies indicated that CPA-loaded chitosan microparticles had higher mucoadhesive properties compared to mannitol particles. Ex vivo studies on sheep nasal mucosa showed that mannitol microparticles promoted CPA permeation across the mucosa, whereas chitosan microparticles controlled CPA permeation rate in comparison with CPA raw material. In vivo studies were carried out on rats. No CPA was detected in rat cerebrospinal fluid (CSF) and brain sections after intravenous administration. In contrast, after nasal administration of loaded microparticles CPA was found in the CSF at concentrations ranging from high nM to microM values and up to two order of magnitude higher than those obtained at systemic level. CPA was also found in the olfactory bulb at concentrations around 0.1 ng/mg of tissue. These results can open new perspectives for the employment of CPA against brain damages following stroke.