Structure-property relationships on recrystallized ß-cyclodextrin solvates: A focus on X-ray diffractometry, FTIR and thermal analyses.

The goal of the study was to evaluate the influence of the solvent properties on the crystal characteristics of ß-cyclodextrin (ß-CD) recrystallized from alcohol-water solvent mixtures, with possible applications for the preparation, purifying and complexation of ß-CD. For the first time, structure-property relationships (QSPRs) between the hydrophobicity of alcohols or dielectric constant of solvents used for recrystallization of ß-CD and its properties (such as crystallinity index, CI) have been obtained. Recrystallized ß-CD from water and C1-C4 alcohol-water solutions provide ß-CD with higher CI values of 99.4(±5.9)% for ethanol-water (1:4, v/v) as recrystallizing system. This property has a parabolic variation with the logP (octanol/water partition coefficient) of the alcohol (r2 = 0.998). Solvent parameters also influence the ß-CD crystal characteristics, as was demonstrated by X-ray diffractometry refinement, infrared spectroscopy and thermal analyses.

Thermal behaviour of procaine and benzocaine Part II: compatibility study with some pharmaceutical excipients used in solid dosage forms.

BACKGROUND: The compatibility study of active substances with excipients finds an important role in the domain of pharmaceutical research, being known the fact that final formulation is the one administered to the patient. In order to evaluate the compatibility between active substance and excipients, different analytical techniques can be used, based on their accuracy, reproducibility and fastness. RESULTS: Compatibility study of two well-known active substances, procaine and benzocaine, with four commonly used excipients, was carried out employing thermal analysis (TG/DTG/HF) and Fourier Transform Infrared Spectroscopy (UATR-FT-IR). The selected excipients were microcrystalline cellulose, lactose monohydrate, magnesium stearate and talc. Equal proportion of active substance and excipients (w/w) was utilized in the interaction study. The absolute value of the difference between the melting point peak of active substances and the one corresponding for the active substances in the analysed mixture, as well the absolute value of the difference between the enthalpy of the pure active ingredient melting peak and that of its melting peak in the different analysed mixtures were chosen as indexes of the drug-excipient interaction degree. All the results obtained through thermal analysis were also sustained by FT-IR spectroscopy. CONCLUSIONS: The corroboration of data obtained by thermal analysis with the ones from FT-IR spectroscopy indicated that no interaction occurs between procaine and benzocaine, with microcrystalline cellulose and talc, as well for the benzocaine-lactose mixture. Interactions were confirmed between procaine and benzocaine respectively and magnesium stearate, and for procaine and lactose.

Influence of emulsifiers on the characteristics of polyurethane structures used as drug carrier.

BACKGROUND: Emulsifiers have a significant role in the emulsion polymerization by reducing the interfacial tension thus increasing the stability of colloidal dispersions of polymer nanostructures. This study evaluates the impact of four emulsifiers on the characteristics of polyurethane hollow structures used as drug delivery system. RESULTS: Polyurethane (PU) structures with high stability and sizes ranging from nano- to micro-scale were obtained by interfacial polyaddition combined with spontaneous emulsification. The pH of PU aqueous solutions (0.1% w/w) was slightly acidic, which is acceptable for products intended to be used on human skin. Agglomerated structures with irregular shapes were observed by scanning electron microscopy. The synthesized structures have melting points between 245-265°C and reveal promising results in different evaluations (TEWL, mexametry) on murine skin. CONCLUSIONS: In this study hollow PU structures of reduced noxiousness were synthesized, their size and stability being influenced by emulsifiers. Such structures could be used in the pharmaceutical field as future drug delivery systems.

Comparative kinetic analysis on thermal degradation of some cephalosporins using TG and DSC data.

BACKGROUND: The thermal decomposition of cephalexine, cefadroxil and cefoperazone under non-isothermal conditions using the TG, respectively DSC methods, was studied. In case of TG, a hyphenated technique, including EGA, was used. RESULTS: The kinetic analysis was performed using the TG and DSC data in air for the first step of cephalosporin's decomposition at four heating rates. The both TG and DSC data were processed according to an appropriate strategy to the following kinetic methods: Kissinger-Akahira-Sunose, Friedman, and NPK, in order to obtain realistic kinetic parameters, even if the decomposition process is a complex one.The EGA data offer some valuable indications about a possible decomposition mechanism. The obtained data indicate a rather good agreement between the activation energy's values obtained by different methods, whereas the EGA data and the chemical structures give a possible explanation of the observed differences on the thermal stability. A complete kinetic analysis needs a data processing strategy using two or more methods, but the kinetic methods must also be applied to the different types of experimental data (TG and DSC). CONCLUSION: The simultaneous use of DSC and TG data for the kinetic analysis coupled with evolved gas analysis (EGA) provided us a more complete picture of the degradation of the three cephalosporins. It was possible to estimate kinetic parameters by using three different kinetic methods and this allowed us to compare the Ea values obtained from different experimental data, TG and DSC. The thermodegradation being a complex process, the both differential and integral methods based on the single step hypothesis are inadequate for obtaining believable kinetic parameters. Only the modified NPK method allowed an objective separation of the temperature, respective conversion influence on the reaction rate and in the same time to ascertain the existence of two simultaneous steps.

[Thermal stability evaluation of some W/O/W double emulsions containing 1% piroxicam by rheological measurements]. / Evaluarea stabilitatii termice a unor emulsii duble H/L/H cu piroxicam prin determinari reologice.

UNLABELLED: The aim of this work was to evaluate thermal stability of some W/O/W concentrated double emulsions (with 80% dispersed phase) containing 1% piroxicam following their theological behaviour at various temperatures. W/O/W double emulsions containing 1% piroxicam were prepared using the two-step procedure. RESULTS: The variable parameter of formulations was the hydrophilic macromolecule compound dispersed in the internal and external aqueous phases (hydroxyethylcellulose and Carbopol 940). Rheological behaviour and viscosity of the obtained W/O/W double emulsions was measured at 15 degrees C, 20 degrees C, 25 degrees C, 30 degrees C and 35 degrees C respectively, after preparation. The obtained results demonstrated that the studied W1/O/W2 double emulsions containing 1% piroxicam were stable under applied thermal stress, although they exhibited some differences in rheological properties caused by formulation variable.

[Skin toxicity of sodium lauryl sulfate as evidenced in an animal model]. / Toxicitatea cutanata, a lauril sulfatului de sodiu evidentiata pe model animal.

This study presents the toxic effects of a very known and used compound in pharmaceutical products and from cosmetic market, a detergent (surface-active) anionic. The presented data underlined the effects of an ointment base with sodium lauryl sulfate, with various concentrations of this detergent, respectively: 0.5%, 1% and 3%, in a long term utilization of this, on an animal model with Sprague Dawley rats.