Response surface optimization,Ex vivoandIn vivoinvestigation of nasal spanlastics for bioavailability enhancement and brain targeting of risperidone
Transnasal brain drug targeting could ensure better drug delivery to the brain through the olfactory pathway. Risperidone bioavailability is 66% in extensive metabolizers and 82% in slow metabolizers. The aim of this study is to investigate the ability of the nanovesicular spanlastics to effectively deliver risperidone through the nasal route to the brain and increase its bioavailability. Spanlastics formulae, composed of span and polyvinyl alcohol, were designed based on central composite statistical design. The planned formulae were prepared using ethanol injection method. The prepared formulae were characterized by testing their particle size, polydispersity index, zeta potential and encapsulation efficiency. The optimized formula having the lowest particle size, polydispersity index, the highest zeta potential and encapsulation efficiency was subjected to further investigations including characterization of its rheological properties, elasticity, transmission electron microscopy, in vitro diffusion, ex vivo permeation, histopathology and in vivo biodistribution. The optimized formula was composed of 5 mg/mL span and 30 mg/mL polyvinyl alcohol. It showed significantly higher transnasal permeation and better distribution to the brain, when compared to the used control regarding the brain targeting efficiency and the drug transport percentage (2.16 and 1.43 folds increase, respectively). The study introduced a successful and promising formula to directly and effectively carry the drug from nose to brain.