Biomedical subjects

I Vélaz

Publications and source records attributed to I Vélaz.

4 recordsLinked to original sources

PubMed1999

Evidence for polymorphism in glisentide.

The polymorphism of glisentide has been investigated. Three polymorphs (I, II, III) have been prepared by recrystallization from different solvents and other polymorphic form (IV) was obtained by heating polymorph III at 100 degrees C. In addition, two 1:1 stoichiometric solvates containing carbon tetrachloride and dioxane have been crystallized and finally, an amorphous solid has been obtained. It has been observed that the polarity of the recrystallisation solvent and its ability to form hydrogen bonds have a great influence on the polymorphism of glisentide. The different solid forms of glisentide have been characterized using X-ray diffraction analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), IR spectroscopy and optical microscopy. The recrystallization of polymorph I in melted form II and also the transition of form III-IV have been detected by DSC and X-ray diffraction analysis.

Benzamides↗

PubMedDate not supplied

Inclusion complexes of nabumetone with beta-cyclodextrins: thermodynamics and molecular modelling studies. Influence of sodium perchlorate.

Fluorescence, (1)H-NMR and molecular mechanics have been used to study the inclusion complexes of nabumetone (4,6-methoxy-2-naphthyl-butan-2-one; NAB) with beta-cyclodextrin (beta-CD), randomly methylated-beta (M beta-CD) and hydroxypropyl-beta-cyclodextrins (HP beta-CD). The emission spectrum of NAB shows a maximum whose fluorescence intensity increases with the different beta-CDs growing concentrations. This phenomenon allows calculation of the stability constants at 15, 25, 37 and 45 degrees C. The thermodynamic parameters Delta H degrees and Delta S degrees for the inclusion process were obtained from the temperature dependence of the stability constants. Molecular mechanics calculations, together with proton NMR measurements, for the complex with beta-CD prove that the complex can be formed by penetration through any of the rims, with the naphthalene nucleus included and the substituents outside the cavity. The influence of NaClO(4) in the aforementioned complexes has been analysed by spectrofluorimetric measurements. It has been found that the stability constants for the complexes decrease with the salt concentration; the causes are discussed.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMedDate not supplied

Effect of PEG 4000 on the dissolution rate of naproxen.

Naproxen is a nonsteroidal anti-inflammatory drug characterized by its low wettability and poor water solubility. Solid dispersions naproxen:PEG 4000 have been prepared in order to improve the solubility and dissolution rate of the drug, since these factors can be the limiting steps for absorption and bioavailability of poorly soluble drugs. X-ray diffraction analysis, infrared spectroscopy and differential scanning calorimetry detected no physico-chemical interaction between the drug and the inert carrier PEG 4000. The phase diagram of the naproxen-PEG 4000 system produced by DSC and hot stage microscopy is reported. The intrinsic dissolution rate of naproxen is calculated. The dissolution kinetics of solid dispersions prepared by the solvent and melt methods are compared with those of free drug and physical mixture. The studies were carried out at 37 degrees C and pH 1.2 according to the dispersed amount method. The dissolution profiles obtained indicate that a significant dissolution enhancement occurs with solid dispersions in comparison with the physical mixture. In addition, the physical mixture showed a dissolution rate higher than the free drug. Dissolution rate constants were determined by fitting the experimental data to the cube root function, to get straight line plots.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMedDate not supplied

Dissolution kinetics for coprecipitates of diflunisal with PVP K30.

Diflunisal is a nonsteroidal anti-inflammatory drug that is poorly soluble in water. The present study describes the formulation of solid dispersions of the drug designed to increase its solubility. X-ray diffraction and DSC were used to examine the physico-chemical characteristics of solid dispersions of diflunisal and polyvinylpyrrolidone (PVP) prepared by the solvent method, using percentage proportional compositions ranging from 20:80 to 50:50. X-ray diffraction analysis detected that diflunisal is present in solid dispersions in crystalline or amorphous state depending on the PVP content. The thermal behavior of diflunisal observed in the DSC curves of solid dispersion systems, was attributed to a solid-state interaction. The increased release of the PVP-drug dispersion as compared to the PVP-drug physical mixture was attributed to the formation of a complex resulting from the interaction of the drug and the polymer.

Anti-Inflammatory Agents, Non-Steroidal↗