Compatibility study of tobramycin and pharmaceutical excipients using differential scanning calorimetry,FTIR, DRX,and HPLC

Differential scanning calorimetry (DSC), isothermal stress testing–Fourier transform infrared spectroscopy (IST–FTIR), isothermal stress testing–high-performance liquid chromatography, and powder X-ray diffraction (PDRX) were used as screening techniques for assessing the compatibility of tobramycin with some currently employed ophthalmic excipients. In the first phase of the study, DSC was used as a tool to detect any interaction. The absolute value of the difference between the enthalpy of the pure tobramycin melting peak and that of its melting peak in the different analyzed mixtures was chosen as a parameter of the drug–excipient interaction degree. DSC results demonstrated that benzalkonium chloride, monobasic sodium phosphate, boric acid, edetate disodium, sodium metabisulfite, thimerosal, and potassium sorbate interact with tobramycin. Taking into account these results, it could be suggested that some of the changes observed in the IST–FTIR spectra of binary blends of tobramycin and some of the excipients would account for a possible interaction between the mixture component. In this study, PDRX did not provide much information, since only tobramycin–thimerosal interactions could be detected. DSC and IST–FTIR are suitable and simple methods for the detection of potential incompatibilities between active pharmaceutical ingredient (API) and excipients.

     

Study of lead levels in soils by weathering of metallic Pb bullets used in dove hunting in Córdoba,Argentina

A study of level of Pb in soils of the center‐north of the Province of Córdoba, a worldwide recognized tourist region for dove hunting, was performed in this work. The native forest of the region has a great population of doves associated with the grain‐productive fields of the surrounding. Contamination of soils due to hunting activities is regulated by national and local norms. The Córdoba Environmental Secretary by resolution no. 1115/2011 approved a new regulation that categorizes this activity as generator of Y31 (Pb) industrial waste. Lead from pellets alloy is deposited on the soil of the shooting fields. Samples were taken at depth of 50 mm from 315 pits referenced by GPS in accordance with local environmental authorities as well as the hunting outfitters companies. Sampling sites are distributed between parallels 31 °S (S31) up to 30 °S (S30) and between meridians W64 up to W63. Soils samples were analyzed by X‐ray fluorescence spectroscopy while Pb bullets were analyzed by scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The average concentration obtained for Pb in dry soil sieved (200 mesh) was 80 ppm. Powder XRD patterns of crust material removed from the corroded surface of weathered bullets were obtained. Three Pb mineral compounds were identified by XRD analysis and also studied by optical microscopy and SEM. Copyright © 2014 John Wiley & Sons, Ltd.     

Conformational polymorphism of the antidiabetic drug chlorpropamide

In this paper, the main features of Raman spectroscopy, one of the first choice methods in the study of polymorphism in pharmaceuticals, are presented taking chlorpropamide as a case of study. The antidiabetic drug chlorpropamide (1‐[4‐chlorobenzenesulphonyl]‐3‐propyl urea), which belongs to the sulfonylurea class, is known to exhibit, at least, six polymorphic phases. These forms are characterized not only by variations in their molecular packing but also in their molecular conformation. In this study, the polymorphism of chlorpropamide is discussed on the basis of Raman scattering measurements and quantum mechanical calculations. The main spectroscopic features that fingerprint the crystalline forms are correlated with the corresponding crystalline structures. Using a theoretical approach on the energy dependence of the conformers, simulated molecular torsion angles are plotted versus the formation energy, which provides a satisfactory agreement between the torsion angles at the energy minima and the experimental values observed in the different solid forms of chlorpropamide. Copyright © 2011 John Wiley & Sons, Ltd.     

Rosiglitazone maleate 0.25‐hydrate: a pseudopolymorphic form

The present 0.25‐hydrated form of rosiglitazone maleate [systematic name: (±)‐2‐({2‐[2,4‐dioxo‐1,3‐thiazolidin‐5‐ylmethyl)phenoxy]ethyl}methylamino)pyridinium maleate 0.25‐hydrate], C₁₈H₂₀N₃O₃S⁺·C₄H₃O₄⁻·0.25H₂O, is a racemate with two independent moieties in the unit cell. Although the cation geometry does not differ substantially from that in the previously reported hydrochloride, the packing is quite different, the main feature being the formation of hydrogen‐bonded tetramers, linked head‐to‐tail into weakly interacting chains.