PubMed · 11398795
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A Anthony. 2001. Why the mesenteric margin?. https://doi.org/10.1053/gast.2001.25310
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An experimental design methodology has been applied to the enantioseparation of a new synthesized aryl propionic acid of pharmaceutical interest, namely 2-[(4'-benzoyloxy-2'-hydroxy)phenyl-propionic acid] (DF-1770y) by chiral capillary zone electrophoresis (CCZE). The chiral separation of the studied compound has been achieved employing vancomycin as the chiral selector. The partial filling-counter current method has been used in order to avoid the presence of the absorbing chiral selector in the path length of the detector and to increase the method sensitivity. A central composite design has been employed to optimize the experimental conditions for a fast separation of the enantiomers of the new synthesized aryl propionic acid. Critical parameters such as chiral selector concentration, pH and temperature have been studied to evaluate how they affected responses such as resolution and migration times. The desirability function approach has been employed in order to find the best compromise between the different experimental responses. The proposed CCZE method provided the baseline enantioseparation of the investigated drug. A Britton-Robinson buffer at pH 6.4 supplemented with 7 mM of vancomycin at 22 degrees C and -20 kV were the optimum experimental conditions allowing to achieve the highest enantioresolution of DF-1770y in less than 8.5 min.
Ground mixtures of naproxen with amorphous beta-cyclodextrin-epichlorohydrin soluble (betaCd-EPS) or insoluble cross-linked (betaCd-EPI) polymers were investigated for both solid phase characterization (Differential Scanning Calorimetry, powder X-ray Diffractometry) and dissolution properties (dispersed amount method). The effect of different grinding conditions and of drug-to-carrier ratio was also evaluated. Co-grinding induced a decrease in drug crystallinity to an extent which depended on the grinding time, and was most pronounced for the cross-linked insoluble polymer, particularly in combinations at the lowest drug content. Both cyclodextrin polymers were more effective in improving the naproxen dissolution properties, not only than the parent betaCd but also than hydroxyalkyl-derivatives, and their performance was almost comparable to that of methyl-derivatives, previously found as the best carriers for naproxen. Dissolution efficiencies of naproxen from physical mixtures with betaCd-EPS, thanks to the high water solubility of this Cd-derivative, were up to three times higher than those from the corresponding products with betaCd-EPI. However this difference in their performance became much less evident in co-ground products and tended to progressively diminish with increasing the polymer content in the mixture, according to the better amorphizing power shown by betaCd-EPI during the co-grinding process. The 10/90 (w/w) drug-carrier co-ground products exhibited the best dissolution properties, giving dissolution efficiencies about 30 times higher than that of naproxen alone.
The purpose of this study was to prepare amorphous precipitates of the binary system of cimetidine (CIM) and diflunisal (DIF) and to investigate the physicochemical properties of the precipitates. To achieve this, the interaction between CIM and DIF molecules was studied by means of nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) measurements. The binary system of CIM and DIF was found to become amorphous upon precipitation from ethanol solution, without heating or melting. In the thermal analysis by TG-DTA equipped with a mass spectrometer, decarboxylation of DIF was found to occur below its melting temperature. In NMR studies, the chemical shifts of a proton in the imidazole ring of CIM and the carbon to which the DIF carboxyl group is bound were found to change depending on the composition of the binary system. The change in NMR chemical shifts suggested that a salt was formed between CIM and DIF. The precipitates had higher solubility than intact drugs due to this salt formation. The results suggest that CIM may be useful as an amorphous carrier, without requiring heating or melting, due to the formation of a salt with acidic drugs.