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Biomedical subjects

M D Veiga

Publications and source records attributed to M D Veiga.

6 recordsLinked to original sources
PubMed2002

Interactions of oxyphenbutazone with different cyclodextrins in aqueous medium and in the solid state.

The interactions between a nonsteroidal anti-inflammatory drugs, oxyphenbutazone (OPB), with two cyclodextrins, beta-cyclodextrin (beta-CD) and gamma-cyclodextrin (gamma-CD), have been studied in an aqueous medium and in the solid state. Differential scanning calorimetry, hot stage microscopy, thermogravimetric analysis and X-ray diffraction (XRD) powder have been the techniques used to characterize the interactions in the solid state. Although OPB forms inclusion compounds with beta- and gamma-CD in the aqueous medium, only the OPB/gamma-CD inclusion compound was obtained in the solid state by the kneading method. The XRD powder used at different temperatures has proven be a useful tool in characterizing the behaviour of these binary systems.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

[ST elevation and tension pneumothorax].

We present a case of a sixty-nine-year-old male admitted to the hospital because of an acute respiratory failure that needed intubation and mechanical ventilation. Shortly after several attempts of right and left (the last one successful) subclavian vein cannulation (the last one successful) he developed a bilateral tension pneumothorax with important hemodynamic repercussion, a critical hypoxia and an ST elevation in inferior leads. Other more typical electrocardiographic changes could be observed: decrease in QRS amplitude and diminishing of precordial R voltage. After removing the air of the right pleural space, all the electrocardiographic signs disappeared returning to normal without electric or enzymatic assay of myocardial necrosis.

Acute Disease↗
PubMed2000

Influence of surfactants (present in the dissolution media) on the release behaviour of tolbutamide from its inclusion complex with beta-cyclodextrin.

The possible competitive displacement of a drug from its cyclodextrin-based inclusion complex by a third substance was investigated by studying the dissolution behaviour of tolbutamide-beta-cyclodextrin inclusion complex in demineralised water and in aqueous solution of different surfactants. Physical mixtures and kneaded systems were prepared in 1:1 and 1:2 drug-beta-cyclodextrin mol/mol ratios and they were characterised by hot-stage microscopy, differential scanning calorimetry, and X-ray powder diffractometry. The release behaviour of tolbutamide from its inclusion complex was studied by studying the dissolution of the binary systems in water and in aqueous solutions of three surfactants: polysorbate 20, poloxyl 23-lauryl ether, and sodium lauryl sulphate. When demineralised water was used as the dissolution media, the fastest dissolution of tolbutamide was obtained from 1:2 kneaded system followed by 1:1 kneaded system. The presence of poloxyl 23-lauryl ether and sodium lauryl sulphate in the media caused a decrement in the rate and extent of dissolution of the drug from both kneaded systems in comparison with that obtained from the same systems in water. However, the release of tolbutamide from the kneaded systems remains unaffected when polysorbate 20 was present in the dissolution media. Results of this study suggest that the simultaneous presence of beta-cyclodextrin and surfactants of proper molecular structure in a pharmaceutical formulation can give rise to an unexpected dissolution of the drug.

Calorimetry, Differential Scanning↗
PubMed2000

Study of tolbutamide-hydroxypropyl-gamma-cyclodextrin interaction in solution and solid state.

Tolbutamide-hydroxypropyl-gamma-cyclodextrin (TBM-HPGCD) interaction has been investigated in an aqueous environment and in the solid state. The solubility of TBM was increased in accord with the amount of HPGCD added to the aqueous medium forming a soluble inclusion compound. The phase solubility diagram obtained was of A(L) type. Physical mixtures and kneaded systems of the drug and cyclodextrin derivative were prepared in 1:1 and 1:2 drug/cyclodextrin mol/mol ratio. All solid binary systems were characterised by hot-stage microscopy (HSM), differential scanning calorimetry (DSC), thermogravimetry (TG) and X-ray powder diffractometry (XRD). An inclusion complex was formed in both of the kneaded systems. In the 1:2 kneaded system, the entire drug was included in the cyclodextrin cavity, while, in the 1:1 kneaded system only a part of the drug formed an inclusion complex with the cyclodextrin. A significant improvement in the dissolution of the drug was obtained from the kneaded systems in comparison with that of the pure TBM and physical mixtures. However, there was no significant difference between the dissolution profiles of the two kneaded systems. The study suggests that an inclusion complex was obtained both in aqueous solution and in solid state.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed1998

Interactions of griseofulvin with cyclodextrins in solid binary systems.

Griseofulvin/cyclodextrin interactions were investigated in aqueous environment and in solid state. Two cyclodextrin derivatives (beta-cyclodextrin and 2-hydroxypropyl beta-cyclodextrin) were used to prepare different physical mixtures and kneaded systems, and the drug/cyclodextrin ratios were 1:1 and 1:2 mol/mol. Scanning electron microscopy (SEM), hot-stage microscopy (HSM), differential scanning calorimetry (DSC), thermogravimetry (TG), and X-ray powder diffractometry were employed to characterize pure substances and their kneaded counterparts and all of the binary systems. The solubility of griseofulvin was increased in accord with the quantity of cyclodextrin added. HSM examination revealed that 2-hydroxypropyl-beta-cyclodextrin was dissolved in the droplets of melted griseofulvin, but did not show any interactions between melted griseofulvin and beta-cyclodextrin particles. The presence of griseofulvin endothermic peak in the DSC curves of all binary systems suggests the absence of any griseofulvin/cylcodextrin inclusion compound in the solid state. In TG, data of weight loss owing to the dehydration of cyclodextrins was similar for both kneaded systems and physical mixtures. X-ray diffraction patterns exhibited the amorphous nature of 2-hydroxypropyl-beta-cyclodextrin and the crystalline nature of griseofulvin and binary systems. Griseofulvin dissolution profiles from all binary systems showed an improvement in drug dissolution, which indicates that an "in situ" drug/cyclodextrin inclusion compound was formed in the aqueous dissolution medium.

2-Hydroxypropyl-beta-cyclodextrin↗