PubMed · 12984692
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J KWOCZEK, W VON MOERS-MESSMER. 1952-05-01. [Dermatological study on sorbit].. https://pubmed.ncbi.nlm.nih.gov/12984692/
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Counterfeit and illegally manufactured drugs become a very important problem all over the world, hence, a search for new fast, easy, reliable and not expensive methods of drugs screening is essential. We describe the use of X-ray powder diffraction method for the fast screening of tablets for counterfeit medicines identification. The original Viagra tablets and some counterfeit and/or imitations of Viagra were used as example. We demonstrate the application of diffraction method for discrimination of tablets coatings and for identification of differences in drug composition. The X-ray diffraction method turns out to be very fast and reliable for detecting counterfeits and imitation, and it correctly predicts the presence or absence of active substance and/or particular excipients.
Uniform polymers are characterised by a narrow molecular weight distribution (MWD). Uniformity is also defined by chemical structure in respect of (1) monomer orientation, sequence and stereo-regularity, (2) polymer shape and morphology and (3) chemical functionality. The function of natural polymers such as polypeptides and polynucleotides is related to their conformational structure (e.g. folded tertiary structure). This is only possible because of their high degree of uniformity. While completely uniform synthetic polymers are rare, polymers with broad structure and MWD are widely used in medicine and the biomedical sciences. They are integral components in final dosage forms, drug delivery systems (DDS) and in implantable devices. Increasingly uniform polymers are being used to develop more complex medicines (e.g. delivery of biopharmaceuticals, enhanced formulations or DDS's for existing actives). In addition to the function imparted by any new polymer it will be required to meet stringent specifications in terms of cost containment, scalability, biocompatibility and performance. Synthetic polymers with therapeutic activity are also being developed to exploit their polyvalent properties, which is not possible with low molecular weight molecules. There is need to utilise uniform polymers for applications where the polymer may interact with the systemic circulation, tissues or cellular environment. There are also potential applications (e.g. stimuli responsive coatings) where uniform polymers may be used for their more defined property profile. While it is not yet practical to prepare synthetic polymers to the same high degree of uniformity as proteins, nature also effectively utilises many polymers with lower degrees of uniformity (e.g. polysaccharides, poly(amino acids), polyhydroxyalkanoates). In recent years it has become possible to prepare with practical experimental protocols sufficient quantities of polymers that display many aspects of uniformity. This review describes practical strategies for polymer synthesis focusing on addition processes that have been developed that allow narrow MWD polymers to be prepared. Also described are some examples where aspects of polymer uniformity in terms of molecular weight and/or chemical constitution are exploited for their unique properties.
The purpose of this study is to investigate the water granulation mechanism of the hydrophilic matrix polymer HPMC in a high shear mixer and to relate the properties of the granules and tablets to the molecular weight and the degree of substitution for eight HPMC grades. Although the hydrophilic matrix system is a well known drug delivery one, there is a difficulty in that the desirable water granulation technique often causes problems in the presence of relatively large amounts of HPMC due to its hydrophilicity. The results of this study show that the properties of the granules and the tablets fall into two groups according to whether the molecular weight of the polymer is high or low. The granules of low molecular weight were smaller and more compact, with better flow properties but with less tensile strength of the compacts, whereas the opposite was valid for granules of high molecular weight. The explanation for these differences is linked to the proposed granulation mechanism of HPMC, in which the properties of the gel layer are important. The dominant factors governing the properties are the molecular weight and, to lesser extent, the degree of substitution.