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Abstract
Delivery of drugs to the large bowel has been extensively investigated during the
last decade. The aim of this study was to investigate whether enteric-coated tablets
could be made from enteric-coated matrix granules and drug release targeted to the
colon. Whether in vitro drug release rate and in vivo absorption could be delayed
by adding citric acid to the granules and/or to the tablet matrix was also studied.
Ibuprofen was used as model drug because it is absorbed throughout the gastrointestinal
tract. Eudragit S and Aqoat AS-HF were used as enteric polymers. Drug release rates
were studied at different pH levels and drug absorption was studied in bioavailability
tests. The conclusion was that citric acid retarded in vitro drug release when used
in multiple-unit tablets. In vivo absorption of ibuprofen was markedly delayed when
citric acid was included in both granules and tablet matrix. Further studies are needed
to determine the optimal amount of citric acid in formulations.