PubMed · 6697925
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R Heinrich. 1984-02-24. [Swallowed coin].. https://pubmed.ncbi.nlm.nih.gov/6697925/
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Silicone microspheres containing pH-sensitive hydrogels are prepared, characterized and evaluated for their potential pH-controlled gastrointestinal (GI) drug delivery. The pH-sensitive hydrogels are semi-interpenetrating polymer networks (semi-IPN(s)) made of varying proportions of poly(methacrylic acid-co-methylmethacrylate) (Eudragit (EUD) L100 or EUD S100) and crosslinked polyethylene glycol 8000 (P8000C). Up to 35 wt% hydrogel particles of mean volume diameters from 89 to 123 microm, medicated with 15 wt% prednisolone (PDN), are encapsulated, with 100% efficiency, into morphologically acceptable silicone microspheres in the 500-1000 microm size range, by a modified emulsion vulcanization method. Microspheres are eluted for 9 h with isotonic fluids at pH values increasing from 1.2 to 7.4, to simulate transit across the GI regions. PDN release depends on dissolution medium pH and on hydrogel composition, which determines hydrogel pH-sensitivity. With the P8000C-EUD L100 (1:2) semi-IPN, the release shows a marked peak at pH 6.8. The P8000C-EUD S100 (1:2) semi-IPN causes a gastroprotection and an almost uniform distribution of released drug between media at pH 6.8 and 7.4. With the P8000C-EUD S100 (1:1) semi-IPN, the dose fraction released to gastric fluid increases to match the values for the media at pH 6.8 and 7.4. With the pH-insensitive, highly swelling, P8000C, the largest dose fraction is released to the gastric medium and release is of Fickian type. With semi-IPNs, release depends weakly on the buffer molarity of the dissolution medium, a reduction from 0.13 to 0.032 of which renders the release rate to the media at pH 6.8 and 7. 4 more uniform.
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Patients receiving cancer therapy are afflicted with a diversity of side effects. Radiotherapy for cancer affecting the head and neck, oesophagus and pelvis is associated with a marked toxicity, specifically encountered as mucosal toxicity. Pain and diarrhoea as well as nausea and vomiting are the most common symptoms, with subsequent problems such as malnutrition and decreased quality of life. These side effects need to be reduced if we are to optimize radiotherapy and to cure patients. Because there is no straightforward way of obviating these side effects, every effort to prevent aggravation and to induce healing of mucosal changes is of prime importance. Numerous agents including antimicrobials, local and systemic analgesics, anti-inflammatory drugs, anti-diarrhoeal drugs, and mucosal protectors alone or in combination with dietetic care have been used and/or are under evaluation in order to palliate the symptoms and increase the quality of life for the patients subjected to radiotherapy. In this article we summarize some aspects within the field that were discussed at the Annual Meeting of the Swedish Society for Oncology in Gavle, 1997.