Vitae (Impact Factor: 0.26). 01/2007;
Source: OAI


Ampicilina, propiedades fundamentales, propiedades derivadas, perfiles de disolución, factor de similitud, concentración mínima inhibitoria.

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Available from: Oscar Florez, Oct 08, 2015
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    ABSTRACT: Incorporation of water molecules in the crystal structure of an organic compound has strong effects on its physical and chemical properties. Therefore, the study on stability of water-incorporated pharmaceutical compounds and mechanisms of hydration and dehydration is very important for the pharmaceutical industries. The main goals of the present research project were quantitative description of the crystallization and solid-state transformations of pseudopolymorphs of sodium naproxen in order to provide fundamental information concerning stability of the pseudopolymorphic forms. Furthermore, macroscopic phenomena of size reduction and anisotropic water-removal by dehydration were rationalized by microscopic aspects of crystal lattice structures. The heats of solution for each pseudopolymorph were estimated by fitting the solubility data with the vant Hoff equation, and their use was extended by the thermodynamic cycle developed in the present study. According to the thermodynamic cycle, for an enantiotropic system, a form with a lower degree of hydration always has the lower heat of solution than a form with a higher degree of hydration, implying that a form with a lower degree of hydration is more stable. The relative stabilities of the dihydrated, the monohydrated, and the anhydrous sodium naproxen at 0% relative humidity were investigated by dehydration of the dihydrated form and powder X-ray diffraction. The monohydrate is more stable than the dihydrate and the result was supported by isothermal TGA experiments. This research explained why powder-like crystals of the anhydrous sodium naproxen were produced by dehydration of hydrated forms. The surfaces of the dehydrated crystals displayed cracks aligned along the b-axis of the monohydrate. These cracks made the anhydrous crystals, which were produced from the monohydrated species, very brittle and, eventually, such crystals were disrupted into much smaller entities. In addition, the existence of water channels in the unit cells of the monohydrate facilitates the dehydration in a direction more rapidly, especially, along the b-axis of the monohydrate. Rapid removal of water in a specific direction caused anisotropic dehydration. Ph.D. Committee Chair: Rousseau, Ronald; Committee Member: Deng, Yulin; Committee Member: Ludovice, Pete; Committee Member: Teja, Amyn; Committee Member: Wilkinson, Angus; Committee Member: Zumstein, Ronald
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    ABSTRACT: The dehydration of ampicillin trihydrate (C16H19N3O4S·3H2O) was studied by both conventional differential scanning calorimetry (DSC) and by pressure differential scanning calorimetry (PDSC). The solid state of the anhydrous phase formed was influenced by the DSC conditions. At ambient pressure, dehydration resulted in the formation of X-ray amorphous anhydrous ampicillin, while at elevated pressures a crystalline anhydrate was obtained. These conclusions were based on variable temperature X-ray powder diffractometry (VTXRD) which was used as a complementary technique. PDSC was a reliable technique to quantify the relative amounts of ampicillin trihydrate and anhydrous ampicillin when they occur as a mixture. Grinding-induced alterations in the degree of crystallinity of ampicillin trihydrate were also quantified by PDSC. The changes in crystallinity induced after milling for just 1 min were detected and quantified with a high degree of precision. PDSC appears to be an excellent technique not only for the characterization but also for obtaining quantitative information about the solid state of pharmaceutical hydrates.
    International Journal of Pharmaceutics 08/1998; 170(1-170):63-72. DOI:10.1016/S0378-5173(98)00123-9 · 3.65 Impact Factor
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    ABSTRACT: Minimum inhibitory concentrations (MICs) are defined as the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation, and minimum bactericidal concentrations (MBCs) as the lowest concentration of antimicrobial that will prevent the growth of an organism after subculture on to antibiotic-free media. MICs are used by diagnostic laboratories mainly to confirm resistance, but most often as a research tool to determine the in vitro activity of new antimicrobials, and data from such studies have been used to determine MIC breakpoints. MBC determinations are undertaken less frequently and their major use has been reserved for isolates from the blood of patients with endocarditis. Standardized methods for determining MICs and MBCs are described in this paper. Like all standardized procedures, the method must be adhered to and may not be adapted by the user. The method gives information on the storage of standard antibiotic powder, preparation of stock antibiotic solutions, media, preparation of inocula, incubation conditions, and reading and interpretation of results. Tables giving expected MIC ranges for control NCTC and ATCC strains are also supplied.
    Journal of Antimicrobial Chemotherapy 08/2001; 48 Suppl 1(suppl 1):5-16. DOI:10.1093/jac/dkf083 · 5.31 Impact Factor
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