Reservoir-Type Subcutaneous Implantable Devices Containing Porous Rate Controlling Membranes for Sustained Delivery of Risperidone

Implantable drug delivery systems are crucial for achieving sustained delivery of active compounds to specific sites or systemic circulation. In this study, a novel reservoir-type implant combining a biodegradable rate-controlling membrane with a drug-containing core prepared using direct compression techniques is developed. The membrane is composed of poly(caprolactone) (PCL), and risperidone (RIS) served as the model drug. Characterization of both membranes and direct compressed pellets includes hardness testing, optical coherence tomography, mercury intrusion porosimetry, and surface morphology observation. In vitro release studies of RIS reveal that higher drug loading in the pellets extended-release duration up to 70 days when incorporated into membranes with four layers. Increasing the number of membrane layers slows the release rate further, ranging from 70 to 170 days depending on membrane thickness. Biocompatibility studies demonstrate that these implantable devices are non-toxic and biocompatible with cells in vitro. In vivo studies conduct in male Wistar rats demonstrate sustained release of RIS, with plasma levels showing a significant increase post-implantation at a relatively constant rate for up to 49 days. These results indicate that the developed implants have the potential to provide long-acting drug delivery to the systemic circulation.