{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,16]],"date-time":"2026-10-16T08:38:21Z","timestamp":1792139901360,"version":"4.4.0"},"reference-count":45,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2024,12,7]],"date-time":"2024-12-07T00:00:00Z","timestamp":1733529600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pharmaceutics"],"abstract":"<jats:p>Background: 5-Aminosalicylic acid (5-ASA), the first-line therapy for ulcerative colitis, is a poorly soluble zwitterionic drug. Unformulated 5-ASA is thought to be extensively absorbed in the small intestine. Methods: The pH-dependent solubility of 5-ASA in vitro and the intestinal membrane distribution of 5-ASA and its N-acetyl metabolite (AC-5-ASA) after the oral administration of 5-ASA were examined in fed rats. 5-ASA was administered as a suspension in water, 0.1 M HCl, or 0.1 M NaOH to untreated rats or as a solution in 5% NaHCO3 to lansoprazole-pretreated rats. Results: 5-ASA solubility in vitro was higher at pH &lt; 2 and pH &gt; 7. In rats, the 5-ASA and AC-5-ASA were detected mostly in the small intestine at 3 h and in the colonic region at 8 h after administration. The dosing vehicle (suspension or solution) and lansoprazole pretreatment did not significantly affect the pH of the luminal fluid in rats or the 5-ASA distribution in membranes. Conclusions: The 5-ASA distribution in membranes in the proximal intestine was found to be restricted by the intrinsic regional luminal pH, low solubility, and saturable membrane permeability. Unabsorbed 5-ASA in the proximal intestine was delivered to the distal intestine. The higher the oral dose of 5-ASA, the more 5-ASA may be delivered to the distal intestine due to the restricted absorption in the small intestine.<\/jats:p>","DOI":"10.3390\/pharmaceutics16121567","type":"journal-article","created":{"date-parts":[[2024,12,9]],"date-time":"2024-12-09T04:01:37Z","timestamp":1733716897000},"page":"1567","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["5-Aminosalicylic Acid Distribution into the Intestinal Membrane Along the Gastrointestinal Tract After Oral Administration in Rats"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2273-6222","authenticated-orcid":false,"given":"Yorinobu","family":"Maeda","sequence":"first","affiliation":[{"name":"Laboratory of Drug Information Analytics, Faculty of Pharmacy & Pharmaceutical Sciences, Fukuyama University, Hiroshima 729-0292, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuta","family":"Goto","sequence":"additional","affiliation":[{"name":"Laboratory of Drug Information Analytics, Faculty of Pharmacy & Pharmaceutical Sciences, Fukuyama University, Hiroshima 729-0292, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fumiya","family":"Ohnishi","sequence":"additional","affiliation":[{"name":"Laboratory of Drug Information Analytics, Faculty of Pharmacy & Pharmaceutical Sciences, Fukuyama University, Hiroshima 729-0292, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Syoutarou","family":"Koga","sequence":"additional","affiliation":[{"name":"Laboratory of Drug Information Analytics, Faculty of Pharmacy & Pharmaceutical Sciences, Fukuyama University, Hiroshima 729-0292, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Satoshi","family":"Kawano","sequence":"additional","affiliation":[{"name":"Laboratory of Drug Information Analytics, Faculty of Pharmacy & Pharmaceutical Sciences, Fukuyama University, Hiroshima 729-0292, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuhzo","family":"Hieda","sequence":"additional","affiliation":[{"name":"Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 1 Sanzo, Fukuyama 729-0292, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Takeshi","family":"Goromaru","sequence":"additional","affiliation":[{"name":"Laboratory of Drug Information Analytics, Faculty of Pharmacy & Pharmaceutical Sciences, Fukuyama University, Hiroshima 729-0292, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6982-0822","authenticated-orcid":false,"given":"Teruo","family":"Murakami","sequence":"additional","affiliation":[{"name":"Faculty of Pharmaceutical Sciences, Hiroshima International University, 5-1-1 Hiro-koshingai, Kure 737-0112, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,12,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Rubin, D.C., Shaker, A., and Levin, M.S. 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