Ground Calcium Carbonate as a Low Cost and Biosafety Excipient for Solubility and Dissolution Improvement of Praziquantel

Calcium carbonate is an abundant mineral with several advantages to be a successful carrier to improve oral bioavailability of poorly water-soluble drugs, such as praziquantel. Praziquantel is an antiparasitic drug classified in group II of the Biopharmaceutical Classification System hence characterized by high-permeability and low-solubility. Therefore, the dissolution rate is the limiting factor for the gastrointestinal absorption that contributes to the low bioavailability. Consequently, the therapeutic dose of the praziquantel must be high and big tablets and capsules are required, which are difficult to swallow, especially for pediatric and elderly patients. Mixtures of praziquantel and calcium carbonate using solid-solid physical mixtures and solid dispersions were prepared and characterized using several techniques (X-ray diffraction differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, laser diffraction, Fourier transform infrared and Raman spectroscopies). Solubility of these formulations evidenced that the solubility of praziquantel-calcium carbonate interaction product increased in physiological media. In vitro dissolution tests showed that the interaction product increased the dissolution rate of the drug in acidic medium. Theoretical models were studied to understand this experimental behavior. Cytotoxicity and cell cycle studies were performed, showing that praziquantel-calcium carbonate physical mixture and interaction product were biocompatible with the HTC116 cells, because it did not produce a decrease in cell viability or alterations in the cell cycle.

Photo-Oxidation of Tetracycline Adsorbed in Clayand in Aqueous Suspension

The resistance of some compounds to conventional treatments engenders the search for alternative methods, such as photo-oxidation. Antibiotics and photo-producers are found in the environment, indicating that these compounds are persistent. This work had as its goal to investigate the photo-oxidation of the antibiotic named tetracycline hydrochloride adsorbed in montmorilloniteclay (VHS) and into aqueous suspension. In order to irradiate the interaction products 0,03g were weighed and put in a petri dish to be collected on pre-determined times. The extraction of the drug was made by adding 10 mL of distilled water and put on the ultrasound for 2 hours. The suspensions were prepared by using 200 mL of the concentration from 25mgL-1of tetracycline in 1gL-1g of clay in a borosilicate reactor. This system was stirred in the dark during 1 hour in order to achieve its balance. The samples were radiated by using an Ultra-Vitalux UV lamp, with 300 W for 2 hours. The kinetics were followed through UV-Vis spectroscopy, monitored in 359 nm, in the maximum wavelength of the drug. The suspensions showed a degradation twice as fast when compared to the interaction product, for the rate of degradation of this system was 24%. This decrease on the concentration may have been caused by the hydroxyl radicals generated by the photolysis of the iron hydroxide II. Hence, one concludes that in the case of the system in suspension it was more effective to the photo-oxidation of this antibiotic. Although, there is the need for increasing the exposure time of the interaction product in order to verify possible structural changes of this system by DRX.

Thermal Reaction and Phase Evolution of APP/Al(OH)3/α-SiO2

The thermal reaction and phase evolution of APP/Al (OH)3/α-SiO2 with different mass ratios during heating were studied by TG, FTIR, XRD and SEM, respectively. When the temperature is not higher than 300 oC, mass ratio of mAPP:mAl (OH)3:mSiO2 has no effect on the phase evolution of APP/Al (OH)3/α-SiO2 and the main interaction product is AlNH4HP3O10. APP/Al (OH)3/α-SiO2 with lower content of APP, appears larger weight loss rate due to the thermal decomposition of Al (OH)3. The thermal reaction of APP/Al (OH)3/α-SiO2 is significantly influenced by the APP content as temperature rises to higher than 300 oC. The decomposition products of APP can chemically interact with Al (OH)3 to generate Al2P6O18 and Al (PO3)3 during 600 oC ~900 °C. When the content of APP increases, much more APP can chemically react with Al (OH)3 and also with part of α-SiO2 to generate SiP2O7. SEM shows the relatively dense microstructure due to micro-bridges of liquid phase with phosphate content increasing.

Microstructure and Compound Developed from the Ce-As-Fe at 1173K

In this study, a certain amount of Cerium and Arsenic were closed in the barrel-shaped cylinder machined by H08 steel, heated to 1173 K for 50 h, and the interaction among the cerium, arsenic and iron in the barrel-shaped cylinder was studied by X-ray diffraction, optical microscopy and electronic probe microscopy analysis. The result shows that the gray phase is the ternary compound Ce12Fe57.5As41, and the ternary compound Ce12Fe57.5As41 is the main interaction product when the atomic ratio of Ce to As is 1:3. The eutectic compound Fe2As can be precipitated from ferrite with the temperature decreasing.