Reservoir-type intranasal implants for sustained release of risperidone: a potential alternative for long-term treatment of schizophrenia

To overcome the challenges of the blood-brain barrier for drug delivery to the central nervous system (CNS), intranasal implants were developed to improve the management of CNS conditions, such as schizophrenia. In the present work, we developed and characterised a drug-containing implant consisting of two parts: a core layer made from risperidone (RIS) and water-soluble polymers, including poly(vinylpyrrolidone) (PVP) and poly(ethylene glycol) (PEG), and a coating layer made of poly(caprolactone) (PCL) membrane. The obtained implants, where the core layer contained 75% w/w risperidone, were characterised using several techniques: scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and attenuated total reflectance-Fourier transform infrared (ATR-FTIR). Moreover, the in vitro release profile of RIS was studied, showing that the PCL membrane could extend the release of RIS from 2 days up to 100 days. The in vitro release profile of the PCL-coated implant exhibited a linear release over the first 10 days, followed by a slower release rate that reached another linear phase up to 40 days. Subsequently, the drug release rates progressively slowed down. Finally, the results of in vitro biocompatibility studies indicated that the intranasal implants were biocompatible and non-cytotoxic. These findings suggest that the implants prepared in this work have the potential to provide long-acting drug delivery for targeting the brain.