Biomedical subjects

João F Pinto

Publications and source records attributed to João F Pinto.

5 recordsLinked to original sources

PubMed2006

Compressed mini-tablets as a biphasic delivery system.

Compressed mini-tablets systems are presented as a biphasic delivery system designed for zero-order sustained drug release. The outer layer that fills the void spaces between the mini-tablets was formulated to release the drug in a very short time (fast release), while the mini-tablets provided a prolonged release. Different composition (HPMC or EC) and number (10 or 21) of mini-tablets were used to obtain different drug release rates. The in vitro performance of these systems showed the desired biphasic behaviour: the drug contained in the fast releasing phase (powder enrobing the mini-tablets) dissolved within the first 2 min, whereas the drug contained in the mini-tablets was released at different rates, depending up on formulation. Based on the release kinetic parameters calculated, it can be concluded that mini-tablets containing HPMC were particularly suitable approaching to zero-order (constant) release over 8h time periods.

Algorithms↗

PubMed2006

Directly compressed mini matrix tablets containing ibuprofen: preparation and evaluation of sustained release.

Directly compressed mini tablets were produced containing either hydroxypropylmethylcellulose (HPMC) or ethylcellulose (EC) as release controlling agent. The dynamics of water uptake and erosion degree of polymer were investigated. By changing the polymer concentration, the ibuprofen release was modified. In identical quantities, EC produced a greater sustaining release effect than HPMC. Different grades of viscosity of HPMC did not modify ibuprofen release. For EC formulations, the contribution of diffusion was predominant in the ibuprofen release process. For HPMC preparations, the drug release approached zero-order during a period of 8 h. For comparative purposes, tablets with 10 mm diameter were produced.

Cellulose↗

PubMed2006

Evaluation of the performance of a new continuous spheronizer.

This study aims to evaluate the performance of a new continuous spheronizer with multiple concentric chambers. The characteristics of the pellets produced in the different chambers (moisture content, mechanical strength, density, sphericity, size, release of a drug) were compared by multivariate analysis of variance (MANOVA), when different times of spheronization and chambers were considered. The statistical analysis has shown that both the diameter of the chambers and the time of spheronization affected the properties of the pellets, and, thus, they must be considered when the spheronizer is used. To minimize these effects all the forming pellets should be processed in all chambers for a defined period of time.

Cellulose↗

PubMed2004

Evaluation of the potential use of poly(ethylene oxide) as tablet- and extrudate-forming material.

The purpose of this study was to assess the potential use of poly(ethylene oxide) (PEO) as matrix-forming material for tablets and extrudates. Raw materials were characterized for size, size distribution, and shape. Tablets with 2- and 10-mm diameter were prepared by direct compression at both 13 and 38 MPa from mixtures with poly(ethylene oxide)s, a model drug (propranolol hydrochloride), and lactose. To these mixtures water was added (16%-43%) prior to extrusion in a ram extruder fit with different dies (1-, 3-, 6-, and 9-mm diameter and 4-mm length). Tablets and extrudates were characterized for work of compression or extrusion, respectively, relaxation, tensile strength, friability, and drug release. Both PEOs produced tablets easily and with different properties. Some relaxation was observed, particularly for tablets with higher amounts of PEOs. Release of the drug occurred after swelling of the matrix, and between 10% and 70% drug released, a quasi zero-order release was observed for large tablets. Extrusion was possible for formulations with PEO only with amounts of water between 16% and 50%. Both radial and axial relaxation of both plugs and extrudates were observed. Moreover, different extrusion profiles reflected the different behaviors of the different formulations. The model drug was released in the same fashion as observed for the tablets. It was possible to produce tablets by direct compression and extrudates or pellets from those extrudates from different formulations with PEO. Tablets and pellets have shown distinct properties depending upon the PEO considered. Extrusion was particularly complex with different formulations with PEO.

Delayed-Action Preparations↗

PubMed2002

Identification of the most relevant factors that affect and reflect the quality of granules by application of canonical and cluster analysis.

The production of granules by wet granulation in a fluidized bed was assessed according to two statistical techniques to identify the most relevant factors that affect the quality of the granules. The statistics used include Canonical Analysis and Cluster Analysis. The factors studied, according to a center of gravity design, included the solubility of a model drug, different grades of polyvinylpirrolidone (PVP), the polarity and the rate of administration of the granulation solution, the atomizing air pressure, the inlet air pressure and rate. The properties of the granules considered were the yield, the assay of the drug, the size, the densities (true, bulk and tapped), the friability, the flowability and one compressibility index. Statistical analysis of the factors evaluated has shown that the solubility of the materials and the pressure of the atomizing air in the nozzle were the most critical parameters affecting the quality of the granules. Less relevant were the granulation solution and the grade of PVP. The properties of the granules that best described their quality were the yield and the densities. From the Cluster Analysis it was possible to divide the granules in two clusters, where cluster 1 was identifiable by the yield, the assay, the flowability, and the friability, whereas cluster 2 was better identified by the size of the granules.

Chemistry, Pharmaceutical↗