{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,19]],"date-time":"2026-09-19T21:41:49Z","timestamp":1789854109026,"version":"4.0.1"},"reference-count":18,"publisher":"Oxford University Press (OUP)","issue":"2","license":[{"start":{"date-parts":[[2019,8,2]],"date-time":"2019-08-02T00:00:00Z","timestamp":1564704000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/journals\/pages\/open_access\/funder_policies\/chorus\/standard_publication_model"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2020,3,7]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>Amphetamines, frequently used recreational drugs with high risk of toxicity, are commonly included in urine drug screens. This screening is based on enzyme immunoassay, which is a quick and easy-to-perform technique, but may lack specificity resulting from cross-reactivity with other compounds, causing false positive results. We present two cases of presumed false positive MULTIGENT\u00ae amphetamine\/methamphetamine and MULTIGENT\u00ae ecstasy (Abbott\u00ae) immunoassays with the beta-blocker metoprolol. Both metoprolol-poisoned patients presented positive urine screening despite no history of drug abuse. No confirmation for amphetamine molecular structures was found with gas chromatography\u2013mass spectrometry. The cross-reactivity was further investigated by doping urine samples with metoprolol and its two major phase-I metabolites. Metoprolol showed positive results for both amphetamine and MDMA tests at low concentrations (200 and 150\u00a0\u03bcg\/mL, respectively). Metoprolol metabolites cross-reacted with the amphetamines immunoassay only, but at higher concentrations (i.e., 2000\u00a0\u03bcg\/mL for \u03b1-hydroxymetoprolol and 750\u00a0\u03bcg\/mL for O-demethylmetoprolol). In conclusion, false positive results in amphetamines and MDMA immunoassays are possible in the presence of metoprolol. Toxicologists should be aware of frequent analytical interferences with immunoassays and a detailed medication history should be taken into consideration for interpretation. In vitro investigation of suspected cross-reactivity should include not only the parent drug but also its related metabolites.<\/jats:p>","DOI":"10.1093\/jat\/bkz051","type":"journal-article","created":{"date-parts":[[2019,6,13]],"date-time":"2019-06-13T19:12:34Z","timestamp":1560453154000},"page":"200-205","source":"Crossref","is-referenced-by-count":20,"title":["False positive amphetamines and 3,4-methylenedioxymethamphetamine immunoassays in the presence of metoprolol\u2014two cases reported in clinical toxicology"],"prefix":"10.1093","volume":"44","author":[{"given":"Marion","family":"Leclercq","sequence":"first","affiliation":[{"name":"Service de Toxicologie, H\u00f4pital Lariboisi\u00e8re, AP-HP, 2 Rue Ambroise Par\u00e9, Paris 75010, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marion","family":"Soichot","sequence":"first","affiliation":[{"name":"Service de Toxicologie, H\u00f4pital Lariboisi\u00e8re, AP-HP, 2 Rue Ambroise Par\u00e9, Paris 75010, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Brigitte","family":"Delhotal-Landes","sequence":"first","affiliation":[{"name":"Service de Toxicologie, H\u00f4pital Lariboisi\u00e8re, AP-HP, 2 Rue Ambroise Par\u00e9, Paris 75010, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Emmanuel","family":"Bourgogne","sequence":"first","affiliation":[{"name":"Service de Toxicologie, H\u00f4pital Lariboisi\u00e8re, AP-HP, 2 Rue Ambroise Par\u00e9, Paris 75010, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Herv\u00e9","family":"Gourlain","sequence":"first","affiliation":[{"name":"Service de Toxicologie, H\u00f4pital Lariboisi\u00e8re, AP-HP, 2 Rue Ambroise Par\u00e9, Paris 75010, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bruno","family":"M\u00e9garbane","sequence":"first","affiliation":[{"name":"Service de R\u00e9animation M\u00e9dicale et Toxicologique, H\u00f4pital Lariboisi\u00e8re, AP-HP, 2 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