Biomedical subjects

D Chulia

Publications and source records attributed to D Chulia.

15 recordsLinked to original sources

PubMed2003

Talc functionality as lubricant: texture, mean diameter, and specific surface area influence.

Talc is widely used as a glidant (flow regulator) for powders. This study highlights the characteristics that confer to talcs new end use properties in improving the lubrication function during compression. We studied the contribution of texture, mean diameter (D50), and specific surface area on the residual die pressure, the ejection pressure, the lubrication index, and the tablet hardness. Different textures were studied: microcrystalline, macrocrystalline, and moderately macrocrystalline talc grade. The compression parameters were improved according to the texture. D50 varies from 0.62 to 15 microm. As D50 decreases, the lubrication performance is improved. Finally, the specific surface area of talcs was studied. This last characteristic of talcs was shown as the most relevant parameter in determining lubrication ability.

Excipients↗

PubMed2002

Influence of manufacturing process on tabletting ability of powder: comparison between blending, grinding, and spray drying of two formulations made of theophylline and lactose/cellulose or Cellactose.

Three manufacturing processes were applied to two formulations composed of 20% anhydrous theophylline associated with either 20% microcrystalline cellulose and 60% lactose or 80% Cellactose. The processing method (dry blending, grinding, or spray drying) and the formulation were investigated through the comparison of the physical and flow characteristics and the compactibility of the end products. The results demonstrated that the formulation had a major effect on the mechanical properties, with binary blends exhibiting a higher resistance than ternary ones, whereas flow properties and densification depended on the process. Nevertheless, it was also observed that spray drying decreased the difference between the mechanical properties of the two formulations, probably by modifying the texture of the Cellactose in suspension.

Bronchodilator Agents↗

PubMed2001

About the use of stoichiometric hydroxyapatite in compression - incidence of manufacturing process on compressibility.

Literature concerning calcium phosphates in pharmacy exhibits the chemical diversity of the compounds available. Some excipient manufacturers offer hydroxyapatite as a direct compression excipient, but the chemical analysis of this compound usually shows a variability of the composition: the so-called materials can be hydroxyapatite or other calcium phosphates, uncalcined (i.e. with a low crystallinity) or calcined and well-crystallized hydroxyapatite. This study points out the incidence of the crystallinity of one compound (i.e. hydroxyapatite) on the mechanical properties. Stoichiometric hydroxyapatite is synthesized and compounds differing in their crystallinity, manufacturing process and particle size are manufactured. X-Ray diffraction analysis is used to investigate the chemical nature of the compounds. The mechanical study (study of the compression, diametral compressive strength, Heckel plots) highlights the negative effect of calcination on the mechanical properties. Porosity and specific surface area measurements show the effect of calcination on compaction. Uncalcined materials show bulk and mechanical properties in accordance with their use as direct compression excipients.

Calcium↗

PubMed1999

The use of energy indices in estimating powder compaction functionality of mixtures in pharmaceutical tableting.

A series of binary powder blends comprising of microcrystalline cellulose (Avicel PH101), alpha-lactose monohydrate or theophylline anhydrous were prepared in order to investigate the densification of binary pharmaceutical powder mixes under compaction pressure. It is postulated that the use of derived energy parameters, as well as various evolved indices, calculated from the work expended during the fabrication and/or rupture of a compact can be employed to quantitatively predict the compaction properties of pharmaceutical powder mixes comprised of the same constituents. The relationship between the net work of compression normalized to powder volume and the resulting compact strength for mix constituents can be used to define a pharmaceutical formulation space in which compact mechanical properties can be estimated for other 'virtual mixes' of the same constituents in different proportions. The approach is successfully applied to the prediction of the mechanical properties of a ternary mix of these constituents.

Chemistry, Pharmaceutical↗

PubMed1999

Effects of true density, compacted mass, compression speed, and punch deformation on the mean yield pressure.

Compressibility properties of pharmaceutical materials are widely characterized by measuring the volume reduction of a powder column under pressure. Experimental data are commonly analyzed using the Heckel model from which powder deformation mechanisms are determined using mean yield pressure (Py). Several studies from the literature have shown the effects of operating conditions on the determination of Py and have pointed out the limitations of this model. The Heckel model requires true density and compacted mass values to determine Py from force-displacement data. It is likely that experimental errors will be introduced when measuring the true density and compacted mass. This study investigates the effects of true density and compacted mass on Py. Materials having different particle deformation mechanisms are studied. Punch displacement and applied pressure are measured for each material at two compression speeds. For each material, three different true density and compacted mass values are utilized to evaluate their effect on Py. The calculated variation of Py reaches 20%. This study demonstrates that the errors in measuring true density and compacted mass have a greater effect on Py than the errors incurred from not correcting the displacement measurements due to punch elasticity.

Pressure↗

PubMed1998

The use of particle characteristics to elucidate mix homogeneity in binary powder blends.

A series of binary powder blends comprising microcrystalline cellulose (Avicel PH101), alpha-lactose monohydrate, or anhydrous theophylline were prepared in order to investigate the ability of particle-characteristics measurements to express the homogeneity of the resulting mixture. It is postulated that fundamental physical characteristics, such as particle-specific surface area, true density, and size distribution, can be used to quantitatively ascertain mix homogeneity in routine pharmaceutical blending operations.

Cellulose↗

PubMed1992

[The therapeutic utilization of magnesium: medical consequences].

To optimize a pharmaceutical formulation, one has to take into account physicochemical, biopharmaceutical, therapeutical and technological properties of the active principle. These properties are investigated in the PREFORMULATION phase. The authors envisage dosage form (capsule) of magnesium and describe two aspects of the active principle: therapeutic and biopharmaceutic.

Animals↗

PubMed1991

[The biodisposition of paracetamol. I. The kinetics of disintegration of some dosage forms].

The in vitro properties of twelve brands of paracetamol (nine tablets and three capsules), commercialized in France, are studied. Among the brands tested (tablets), Latepyrine and Gynospasmine are characterized by faster and Panasorb by slower dissolution rate. Total time of dissolution varies between 7 and 60 min. In some brands, paracetamol is liberated from the surface of the disintegrated particles and in others the active principle is released by progressive erosion. The presence of a surface active agent enhances liquid penetration in the case of capsules.

Acetaminophen↗

PubMed1991

[The bioavailability of paracetamol II. The effect of porosity and mechanical properties of the dosage form on solubility].

The authors attempt to explain differences observed in dissolution rate of twelve different brands of paracetamol (nine tablets and three capsules) in terms of pore structure and tensile strength; the pore structure of both tablets and capsules is investigated by mercury porosimetry. Brands (tablets) which liberate paracetamol rapidly are characterized by a higher porosity value. Higher mean pore diameter signifies less t50 and higher porosity. An increase in tensile strength results in an increase in t50 and a decrease in porosity. Porosity alone cannot dictate the dissolution behaviour of capsules.

Acetaminophen↗

PubMed1989