Enhancement the oral bioavailability of praziquantel by incorporation into solid lipid nanoparticles.

The aim of this study was to assess the feasibility of solid lipid nanoparticles (SLN) to enhance the oral bioavailability of praziquantel (PZQ). SLN loaded with PZQ were produced by ultrasound technique. The characteristics of PZQ-SLN were studied in detail. The concentration of PZQ in plasma was determined using reversed-phase high-performance liquid chromatography after oral administration of PZQ-SLN and control PZQ tablets (PZQ-TAB) in rats respectively. The results showed that PZQ-SLN had an average diameter 110 nm with Zeta potential of -66.3 mV. The encapsulation efficiency of PZQ was about 80%. In vitro drug release fitted the Weibull distribution equation. There were two peaks in the PZQ concentration-time curves in plasma after oral administration of PZQ-SLN. The first peak might be caused by free drug and that adsorbed onto the surface of PZQ-SLN. The second peak was indicative of gut uptake of PZQ-SLN. The AUC(0-infinity) value of PZQ after oral administration of SLN was 4.1 fold higher than that obtained with the PZQ-TAB. The MRT of PZQ-SLN was also significantly enhanced, resulting in an about twofold increase compared with PZQ-TAB. Thus, the oral bioavailability of PZQ-SLN increased significantly compared to PZQ-TAB, and the results indicate that SLN can be a promising drug carrier for PZQ.

Preparation of submicron unilamellar liposomes by freeze-drying double emulsions.

A novel method is described for the preparation of sterile submicron unilamellar liposomes. The method is based on the lyophilization of double emulsions containing disaccharides as lyoprotectants in both the inner and outer aqueous phase. Using various phospholipids or mixtures of lipids as emulsifiers, the double emulsions can be prepared by a two-step emulsification, including hydrophilic agents in the inner aqueous phase or lipophilic agents in the oil phase. Then, the double emulsions are lyophilized after sterilization by passing them through a 0.22-microm pore filter. Rehydration of the lyophilized products results in liposomes with a relatively high encapsulation efficiency (for calcein, 87%; 5-fluorouracil, 19%; flurbiprofen, 93%) and a size below 200 nm measured by the dynamic light scattering technique (DLS) and the atomic force microscopy (AFM). The liposomes were found to be unilamellar from freeze-fracture electron micrographs and X-ray diffraction patterns. In addition, the liposomes can be reconstituted just before use by rehydration of the lyophilized products which are relatively stable. Thus, this reproducible and simple technique can be used to prepare sterilized, submicron unilamellar liposomes with a relatively high encapsulation efficiency, and excellent stability during long-term storage.