[Pharmaceutical contribution to the non specific challenge in bronchial provocation tests]. / Contribution pharmaceutique a l'exploration de l'hyperréactivité bronchique non spécifique.

Aerosols of methacholine chloride are used in inhalation tests to measure non-specific bronchial responsiveness. Inhalation challenge solutions are not commercially available neither by pharmaceutical industry nor in France by the PCH-APHP. To reply to doctor's request, dilute concentrations of methacholine must be prepared properly in order to protect the patient and to assure doctor of test reproductibility. Osmolarity, pH and degradation of different dilute concentration of methacholine chloride have been compared with two diluents. This study allowed us to validate our preparation of solutions.

Determination of homocysteine in plasma by liquid chromatography with fluorescence detection.

A liquid chromatographic (LC) method to assay homocysteine in plasma at micro-molar levels is described. The procedure consists of protein precipitation with trichloroacetic acid and a centrifugation step. The supernatant is then derivatized with a thiol-specific fluorochromophore and LC assayed with fluorescence detection at 385 nm excitation and 515 nm detection. LC analysis is performed by isocratic elution using an acetate buffer (0.05 M, pH 4) as a mobile phase and an alphaBond column. Recoveries based on a five-point standard curve calculation ranged from 96 to 112%. The limits of detection and quantification reached were 0.8 and 1.57 micromol/L, respectively.

Compression behavior of orthorhombic paracetamol.

PURPOSE: Orthorhombic crystals of paracetamol exhibit good technological properties during compression. The purpose of this study was to investigate the compression behavior of this substance and to compare it to that of monoclinic paracetamol. From the crystal structure, it could be hypothesized that sliding planes are present in the orthorhombic form, and could be responsible for an increase in crystal plasticity. METHODS: Compression of pure orthorhombic or monoclinic paracetamol tablets was carried out on a fully instrumented single punch machine. Data was used to establish Heckel's profiles. Images of compressed crystals were obtained by scanning electron microscopy. RESULTS: Tabletability of the orthorhombic crystals was far better than that of the monoclinic ones, and capping was not observed even at high compression pressure. Compared to the monoclinic form, orthorhombic paracetamol exhibited greater fragmentation at low pressure, increased plastic deformation at higher pressure, and lower elastic recovery during decompression. Plastic behavior was confirmed by SEM - micrographs showing that crystals folded under pressure. A compactibility study showed that the nature of interparticle bonds was similar for both polymorphs, the number of bonds being greater for orthorhombic paracetamol. CONCLUSIONS: Unlike the monoclinic form, orthorhombic paracetamol is suitable for the direct compression process. The crystalline structure accounts for its better compression behavior, because of the presence of sliding planes.