RESUMO
Praziquantel (PZQ) is the drug recommended by the World Health Organization for treatment of schistosomiasis. However, the treatment of children with PZQ tablets is complicated due to difficulties to adapt the dose and the extremely bitter taste of PZQ. For this reason, poly (methyl methacrylate) nanoparticles loaded with Praziquantel (PZQ-NP) were developed for preparation of a new formulation to be used in the suspension form. For this reason, the main aim of the present study was to evaluate the pharmacokinetic (PK) profile of PZQ-NP, through HPLC-MS/MS assays. Analyses were performed with an Omnisphere C18 column (5.0 µm×4.6 mm×150.0 mm), using a mixture of an aqueous solution containing 0.1 wt% of formic acid and methanol (15:85-v/v) as the mobile phase at a flow rate of 0.800mL/min. Detection was performed with a hybrid linear ion-trap triple quadrupole mass spectrometer with multiple reactions monitoring in positive ion mode via electrospray ionization. The monitored transitions were m/z 313.18>203.10 for PZQ and m/z 285.31>193.00 for the Internal Standard. The method was validated with the quantification limit of 1.00 ng/mL, requiring samples of 25 µL for analyses. Analytic responses were calibrated with known concentration data, leading to correlation coefficients (r) higher than 0.99. Validation performed with rat plasma showed that PZQ was stable for at least 10 months when stored below -70 °C (long-term stability), for at least 17 h when stored at room temperature (RT, 22 °C) (short-term stability), for at least 47 h when stored at room temperature in auto-sampler vials (post-preparative stability) and for at least 8 successive freeze/thaw cycles at -70 °C. For PK assays, Wistar rats, weighing between 200 and 300 g were used. Blood samples were collected from 0 to 24 h after oral administration of single doses of 60 mg/kg of PZQ-NP or raw PZQ (for the control group). PZQ was extracted from plasma by liquid-liquid extraction with terc-butyl methyl ether. The values obtained for maximum concentration (C(max)) and area under curve (AUC) for the PZQ-NP group were about 3 times smaller than the respective values obtained for the control group. However, the time for achieving maximum concentration (T(max)), the elimination constant (Ke) and the half-life time of elimination (T(½ß)) were not statistically different. These results suggest that PZQ absorption is probably the rate-limiting step for obtainment of better PK parameters for PZQ-NP. Thus, further studies are needed to understand both the PZQ-NP absorption mechanisms and the drug diffusion process through the polymer matrix in vivo, in order to improve the PZQ-NP release profile.