{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T15:25:06Z","timestamp":1787585106648,"version":"build-2736575974"},"reference-count":12,"publisher":"Wiley","issue":"7","license":[{"start":{"date-parts":[[2020,4,1]],"date-time":"2020-04-01T00:00:00Z","timestamp":1585699200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["analyticalsciencejournals.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Drug Testing and Analysis"],"published-print":{"date-parts":[[2020,7]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>Paracetamol is used widely as an over\u2010the\u2010counter analgesic and antipyretic medication for humans, but not for Japanese racehorses. Paracetamol can be an environmental substance, and is found together with its two isomers, metacetamol and orthocetamol, in equine urine. However, the sources and routes of paracetamol exposure remain unclear. To control the misuse of paracetamol, it is appropriate to establish residue limits for paracetamol to differentiate the administration of paracetamol from its environmental levels. In this study, we developed and validated a quantitative method for paracetamol, metacetamol, and orthocetamol in equine plasma using liquid chromatography\u2013electrospray ionization\u2013tandem mass spectrometry and applied it to postrace samples from 320 Japanese racehorses for approximately 1 year. In addition, we conducted feed analysis and related pharmacokinetics simulations to evaluate the contributions from exposure via feed. The hydrolyzed plasma concentrations of paracetamol, metacetamol, and orthocetamol ranged from 0.787 to 39.8 ng\/mL (median 5.87 ng\/mL), 0 to 2.13 ng\/mL (0.347 ng\/mL), and 1.98 to 82.8 ng\/mL (16.6 ng\/mL), respectively. Such low concentrations of paracetamol were deemed irrelevant to therapeutic effect. Based on statistical analysis, the preliminary Japanese residue limits of unhydrolyzed and hydrolyzed paracetamol were determined to be 70.5 ng\/mL and 112 ng\/mL, respectively, in plasma, at a risk factor of 1 in 10,000. Furthermore, we detected paracetamol and orthocetamol in feed samples. A pharmacokinetics simulation showed that the presence of orthocetamol is most probably related to daily feed rations. As for paracetamol, feed can be one of the sources and other possible sources require further investigation.<\/jats:p>","DOI":"10.1002\/dta.2792","type":"journal-article","created":{"date-parts":[[2020,3,18]],"date-time":"2020-03-18T17:15:24Z","timestamp":1584551724000},"page":"929-937","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["Investigation of plasma concentrations of paracetamol, metacetamol, and orthocetamol in Japanese racehorses using liquid chromatography\u2013electrospray ionisation\u2013tandem mass spectrometry"],"prefix":"10.1002","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6850-1894","authenticated-orcid":false,"given":"Hideaki","family":"Ishii","sequence":"first","affiliation":[{"name":"Laboratory of Racing Chemistry, Utsunomiya  Tochigi Japan"},{"name":"Tohoku University Hospital, Tohoku University  Sendai Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Taku","family":"Obara","sequence":"additional","affiliation":[{"name":"Tohoku University Hospital, Tohoku University  Sendai Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Isao","family":"Kijima\u2010Suda","sequence":"additional","affiliation":[{"name":"Laboratory of Racing Chemistry, Utsunomiya  Tochigi Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2020,4]]},"reference":[{"key":"e_1_2_7_2_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jchromb.2015.10.013"},{"key":"e_1_2_7_3_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.2042-7158.1963.tb11193.x"},{"key":"e_1_2_7_4_1","unstructured":"deKockSS MandyK MartinovicST JogiP GuthrieAJ.A study of paracetamol orthocetamol and metacetamol in horseracing in Southern Africa. 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