In vitro and in vivo evaluation of praziquantel loaded implants based on PEG/PCL blends

In the present study, a series of praziquantel (PZQ) loaded implants based on PEG/PCL blends are fabricated by a combination of twin-screw mixing and hot-melt extrusion. In vitro drug release from these implants and the performance of the implants after implantation in rats are evaluated. XRD and DSC analysis results exhibit each component in the implants is mainly in its crystalline state. Dissolution test shows that the higher PEG content there is in the implants, the faster the drug will be released. Interestingly, PEG release from all implants is far faster than PZQ release, and complete PEG release occurs in 72 h. SEM result displays that after the in vitro drug release test, the cross-sections of implants with low PEG contents (0-5%) primarily consist of discrete pores; while those of implants with high PEG contents (10-30%) consist of interconnected pores or channels. The fitting results of drug release data with kinetic models reveal that PZQ release is governed by diffusion. After implantation, drug release becomes more moderate compared with in vitro drug release, and it tends to follow zero-order in the later stage. These results suggest that changing the composition of the PEG/PCL blends is an effective tool to adjust in vitro/in vivo drug release from the implants.