Optimized hydration dynamics in mucoadhesive xanthan-based trilayer vaginal films for the controlled release of tenofovir.

Karaya gum, pectin and xanthan gum have been tested as candidates for manufacturing mucoadhesive trilayer films containing ethylcellulose and chitosan for the vaginal administration of the antiviral Tenofovir (TFV). The swelling profile correlated with the amount of mobile dipoles determined by impedance spectroscopy allows the determination of the hydration dynamics of these films. The fast water penetration has been demonstrated to favor the formation of polyelectrolyte complexes (PEC) via hydrogen or ionic bonds which would favor a controlled release. The incorporation of an inorganic drug release regulator induces the weakness of the polymeric chains thus enhancing the ionic mobility via the formation of low molecular weight PECs in films manufactured with karaya gum. Due to the different mechanical properties of the individual components, pectin-based films failed for a potential pharmaceutical formulation. However, mucoadhesive trilayer films produced with xanthan gum have demonstrated a moderate swelling, improved wettability and a controlled release of TFV.

Robust and versatile pectin-based drug delivery systems.

Pectin-based resistant, interactive and versatile hydrogel vehicles for oral administration have been prepared. These systems are thought to be versatile enough to allow the inclusion of substances (such as the surfactants tested: Pluronic, Tween, Na Lauryl sulphate) that may contribute to tailor the drug release patterns. Tolbutamide, that shows a discrete and pH-dependent solubility in water, has been employed as a model drug to test the capability of these matrices to overcome such drug-imposed restraints. The incorporation of different surfactants produced pectin-based hydrogels of difficult manipulation. In order to improve this drawback, two different strategies have been developed: blending with agarose or freeze-drying. The presence of agarose yields robust systems that can be handled and tested as prepared, in the fresh state. Freeze-drying not only allows to shape pure pectin and blend systems, but also generates a porous structure whose microstructure, determined by the different components included, influences on the drug release behavior. Tolbutamide release kinetics from freshly prepared matrices can be fitted to the Higuchi model while the freeze-dried ones adjust to the Korsmeyer-Peppas model; hence the hydrogel chains rearrangement processes rule the release during the rehydration process.

Agarose drug delivery systems upgraded by surfactants inclusion: critical role of the pore architecture.

Anionic or non-ionic surfactants have been introduced in agarose-based hydrogels aiming to tailor the release of drugs with different solubility. The release of a hydrophilic model drug, Theophylline, shows the predictable release enhancement that varies depending on the surfactant. However, when the hydrophobic Tolbutamide is considered, an unexpected retarded release is observed. This effect can be explained not only considering the interactions established between the drug loaded micelles and agarose but also to the alteration of the freeze-dried hydrogels microstructure. It has been observed that the modification of the porosity percentage as well as the pore size distribution during the lyophilization plays a critical role in the different phenomena that take place as soon as desiccated hydrogel is rehydrated. The possibility of tailoring the pore architecture as a function of the surfactant nature and percentage can be applied from drug control release to the widespread and growing applications of materials based on hydrogel matrices.

[Bronchial nodules produced by Strongyloides stercoralis as the cause of bronchial obstruction]. / Nódulos bronquiales producidos por Strongyloides stercoralis como causa de obstrucción bronquial.

Infection by Strongyloides stercoralis can cause asthma-like symptoms through mechanisms that have not yet been clarified. A 55-year-old male farm worker with a 2-year history of illness diagnosed as asthma and treated unsuccessfully with bronchodilators and corticosteroids was referred to our hospital with severe dyspnea. The initial chest radiograph showed mild air trapping, and pulmonary function tests detected airway obstruction that did not respond to salbutamol. Bronchoscopy revealed multiple nodules protruding into the airway lumen. S. stercoralis larvae were detected in bronchoalveolar lavage fluid and stool samples. Although treatment with albendazole was initiated, the patient's condition worsened over the next 3 days, hemoptysis presented, and the process ended in death. Autopsy demonstrated Strongyloides larvae in the bronchial nodules. Infection by S. stercoralis should be considered in the differential diagnosis of asthmatic-like symptoms refractory to treatment. In such cases nodules may be responsible for obstruction.