Agata Górniak

Thermal, spectroscopic and dissolution studies of lovastatin solid dispersions with acetylsalicylic acid

Lovastatin (LOV) is widely used for the treatment of hypercholesterolemia. The poor water solubility of LOV leads to its poor gastrointestinal absorption and results in poor bioavailability. In this study, a preparation of solid dispersions with acetylsalicylic acid (ASA) was studied to improve the dissolution rate of LOV. Solid dispersions were prepared using various mass ratios of both components through the grinding method. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD) were used to characterize prepared solid dispersions. Their dissolution behaviors were also compared. LOV and ASA formed a simple eutectic phase diagram as indicated by DSC. The results obtained from FTIR spectroscopy and XRPD showed no evidence of drug–drug interaction. The dissolution studies indicated that the in vitro dissolution rate of LOV released from solid dispersions containing 10, 20, 40 and 60 mass% LOV was improved compared with the drug alone.

Thermal stability and decompositions kinetics under non-isothermal conditions of imatinib mesylate α form.

The thermal decomposition and kinetic parameters of synthetized imatinib mesylate α form α form were determined by thermogravimetry (TGA/DTG) under non-isothermal conditions. The experiments were performed at a 25-940°C temperature range at five different heating rates: 2.5Kmin(-1), 5Kmin(-1), 10Kmin(-1), 15Kmin(-1) and 20Kmin(-1) per minute in a nitrogen atmosphere. Imatinib mesylate α form presents one-step mass loss during the degradation process. The thermal stability of the examined material, the melting temperature (Tonset=220.6°C) and ΔH fusion=-95.74Jg(-1) at a heating rate of 10°Cmin(-1) was established. The values of activation energies have been estimated using Kissinger, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods.

Physicochemical characterization and dissolution studies of acyclovir solid dispersions with Pluronic F127 prepared by the kneading method.

Abstract The dissolution rate of anhydrous acyclovir was improved by the preparation of physical mixtures and solid dispersions with the non-ionic polymer Pluronic F127 using the kneading method at different drug-to-polymer ratios. The obtained physical mixtures and solid dispersions were examined in terms of drug content and possible physical and chemical interactions between the drug and polymer using FTIR spectral studies, differential scanning calorimetry and powder X-ray diffraction analysis. The dissolution rate of acyclovir was determined using the rotating disk method. It was found that the minimal content of the polymer within the mixtures needed to increase the dissolution rate of the drug was 50 %.

THE INFLUENCE OF A DENTAL FORMULATION PREPARED WITH CHITOSAN ON THE PHARMACEUTICAL AVAILABILITY OF CLOTRIMAZOLE

The present work involves the development of a dental gel composition obtained on the basis of clotrimazole incorporated into chitosan in order to improve drug solubility. Solid dispersions were prepared by using two methods: grinding and kneading. The solid dispersion varied the ratio of chitosan to drug to increase the volume of the drug; the ratios were 5:5, 3:7, 2:8, 1:9. The mixtures were subjected to the dissolution rate of clotrimazole. The presence of chitosan improved the drug solubility; a better solubility from the solid dispersion prepared by the grinding method was obtained from the ratio of drug to polymer of 1+9. The rate of dissolution of clotrimazole was improved 17 times compared to the pure drug. Fourier transform infrared spectroscopy (both infrared and X-ray diffraction) revealed no new chemical structure of the tested connections and concluded that there was no interaction between the drug and the polymer in the test diffractions. Solid dispersions with the best parameters were used to prepare hydrogels, and the pharmaceutical availability of clotrimazole was analysed. The best properties were characterized by a hydrogel that was composed of the ratio of the amount of drug to polymer 5:5. The study demonstrated the availability of a pharmaceutical drug release at a therapeutic concentration in the first hour of the study. The use of the appropriate balance between clotrimazole and chitosan and the development of the hydrogel composition may affect the improvement of the drug solubility and may create the possibility of obtaining sustained or controlled release of the drug substance. .

PHYSICOCHEMICAL CHARACTERIZATION AND DISSOLUTION STUDIES OF SOLID DISPERSIONS OF CLOTRIMAZOLE WITH CHITOSAN

The aim of the present study was to increase the solubility of clotrimazole. Among the methods to increase the solubility selected solid dispersions of the drug with the polymer. Chitosan was used as the polymer. Clotrimazole was incorporated into the chitosan type 652 with molar masse chitosan Mη = 429 kDa. Solid dispersions were prepared by using different ratios of clotrimazole and chitosan (1:9, 3:7, 5:5, 7:3, 9:1). Formulations were tested dissolution rate of the drug. The highest dissolution of clotrimazole, amounting to 47.95%, was observed after 60 minutes from solid dispersion prepared by grinding method and 42.84% from physical mixtures with drug-polymer weight ratio 1:9 in the presence chitosan. The solubility of the drug improved more than 37-fold. XRPD analysis indicates the presence of the clotrimazole in crystalline form in the solid dispersion obtained by kneading method.

The Electrical Conductivity of Molten (Ag, Cd1/2)Br

Abstract The electrical conductivity of molten (Ag, Cd1/2)Br has been determined as a function of temperature in the whole range of compositions. The resulting activation energy values and the conductivity isotherm at 850 K are compared with those of the system (Ag, Cd1/2)Cl.