Background: Donepezil (DPZ) is widely prescribed as a specific and reversible acetylcholinesterase
inhibitor for the symptomatic treatment of mild to moderate Alzheimer's disease (AD).
Objective: Considering the therapeutic potential of DPZ and the advantages offered by the intranasal
route as an alternative for drug administration, the aim of this study was the development and characterization
of a DPZ microemulsion (ME) for nose-to-brain delivery.
Method: The ME was developed by construction of pseudoternary phase diagrams and characterized
by dynamic light scattering and transmission electron microscopy. Flow properties and viscosity, as
well as optical stability and stability under storage at different temperatures were evaluated. Finally, in
vitro release and ex vivo permeation studies through porcine nasal mucosa were accomplished.
Results: A transparent and homogeneous DPZ-ME (12.5 mg/ml) was obtained. The pH and viscosity
were 6.38 and 44.69 mPa·s, respectively, indicating nasal irritation prevention and low viscosity. The
mean droplet size was 58.9±3.2 nm with a polydispersity index of 0.19±0.04. The morphological
analysis revealed the spherical shape of droplets, as well as their smooth and regular surface. Optical
stability evidenced no destabilization processes. DPZ release profile indicated that the ME followed a
hyperbolic kinetic model while the ex vivo permeation profile showed that the highest permeation occurred
during initial 4 h and the maximum permeated amount was approximately 2000 µg, which corresponds
to 80% of the starting amount of drug.
Conclusion: We conclude that our nasal ME could be considered as a new potential tool for further
investigation in the AD.