Biomedical subjects

Roch Thibert

Publications and source records attributed to Roch Thibert.

3 recordsLinked to original sources

PubMed2003

Physicochemical evaluation of carbamazepine microparticles produced by the rapid expansion of supercritical solutions and by spray-drying.

PURPOSE: To compare the physical and physicochemical characteristics of carbamazepine microparticles prepared using two different methods: (1) the rapid expansion of supercritical solutions (RESS) and (2) the spray-drying process. METHODS: For both processes, microparticles were produced over a range of different temperatures (35 to 100 degrees C). For the RESS method, carbon dioxide was the solvent used over a pressure range of 2500 to 3500 psi. As for the spray-drying method, different organic solvents were used at atmospheric pressure. Comparison was based on morphology, crystalline structure, mean particle size, and size distribution of processed particles. The influence of process parameters on microparticles' characteristics was also investigated. Particles were analyzed using scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), thermogravimetric analyzer (TGA), and differential scanning calorimetry (DSC). RESULTS: The carbamazepine particles used as unprocessed starting material had a mean diameter of approximately 85 microm with a size distribution range between 15 and 336 microm. Microparticles produced by either the RESS or spray-drying method had a mean diameter smaller than 2 microm and a narrower size distribution range between 0.25 and 2.5 microm. SEM photomicrographs, X-ray diffractograms, and DSC spectra revealed that modification of crystal morphology was dependent on the operating conditions. CONCLUSIONS: Significant reduction in mean particle size and size distribution range of carbamazepine particles was observed by RESS and spray-drying methods. The results also demonstrate that the crystalline nature of carbamazepine particles depends on the method of production and on the operating parameters of pressure and temperature.

Carbamazepine↗

PubMed2002

Clickhaler dry powder inhaler: focussed in vitro proof of principle evaluation of a new chemical entity for asthma.

A new chemical entity (NCE) was evaluated in the Clickhaler (Innovata Biomed Ltd.) dry powder inhaler, a reservoir-based multidose delivery system. The standard device metering system was modified to handle higher doses (nominally 20 mm(3) of lactose based blend). The micronized drug was formulated at 12.5% w/w in lactose monohydrate (Pharmatose 325M, DMV) equivalent to a nominal dose of approximately 1 mg. Delivered shot weight (mg of blend) and emitted dose (microg drug) averaged 7.4 mg and 905 microg, respectively, and were consistent (within +/-20 to 25% of mean) through the life of the inhaler. The fine particle fraction (FPF) (Andersen cascade impactor) was typically 60%. A short stability study (i.e. 3 months at room temperature, 53 or 75% RH, unpacked) showed that the in vitro performance was maintained. The results of these studies provide in vitro proof of principle for this novel drug/device combination.

Anti-Asthmatic Agents↗

PubMed2002

New methods characterizing avalanche behavior to determine powder flow.

PURPOSE: To characterize the avalanche behavior of different powders and to compare the results of the strange-attractor and novel characterization approaches. METHODS: The following nine different materials were tested: three lactoses, maltodextrin, two microcrystalline celluloses, sodium chloride, sucrose, and glass beads. Morphology, size, and size distribution, true density, bulk and tap density, angle of repose, flow index, and avalanching behavior were quantified for each excipient by scanning electron microscopy, laser time-of-flight analysis, helium pycnometer, graduated cylinder, fixed-height funnel, Flodex (Hanson Research Corp., Chatsworth, California) method, and AeroFlow (TSI, Inc., St. Paul, Minnesota), respectively. Environmental factors were controlled, and the avalanches were studied at various speeds. RESULTS: The strange-attractor graph obtained at 1 rotation per 120 s showed that it was difficult to appreciate the flowability differences among 3-mm glass beads, lactose 100, and lactose 325. However, plotting the raw data as a relationship of the time between each avalanche and the inverse of speed revealed a characteristic linear slope for each sample. Furthermore, a new flowability index based on the SD calculated from the raw data gave results that were consistent with Carr's index. A cohesive index also can be determined by avalanche behavior, and it reflects the stability of the rapid particular rearrangements of powder. CONCLUSION: A novel method of evaluating avalanche measurements makes it possible to better characterize powder flowability and to predict powder behavior under working conditions.

Lactose↗