Published: Journal of Analytical Toxicology, ISSN 0146-4760, Volume 25, Number 5, July/August, pp. 333-338

The Antispasmodic Drug Mebeverine Leads to Positive Amphetamine Results by Fluorescence Polarization Immunoassay (FPIA)—Studies on the Toxicological Analysis of Urine by FPIA and GC–MS
Thomas Kraemer, Robert Wennig, and Hans H. Maurer
1Department of Toxicology, Institute of Pharmacology and Toxicology, University of Saarland, D-66421 Homburg (Saar), Germany and 2Laboratoire National de Santé, Toxicology Division, Centre Universitaire, L-1511 Luxembourg

Mebeverine (Duspatal®, MB), an antispasmodic drug, is the veratric acid ester of 4-{ethyl-[2-(4-methoxyphenyl)-1-methylethyl]amino}butan-1-ol (MB-OH), which is a N-substituted ethylamphetamine derivative. MB is metabolized via ester hydrolysis to MB alcohol (MB-OH) and veratric acid. N-Dehydroxybutylation leads to methoxyethylamphetamine (MO-EA) and, after O-demethylation, to hydroxy EA (HO-EA). N-Bisdealkylation leads to p-methoxyamphetamine (PMA). MO-EA and PMA are also known as designer drugs. Fluorescence polarization immunoassay (FPIA) and gas chromatographic–mass spectrometric studies on the toxicological analysis of MB after ingestion of a single 405-mg oral dose of MB were performed. We could show that intake of MB leads to positive FPIA results for amphetamine. The N-dehydroxybutyl metabolites of MB, MO-EA, HO-EA, and the bis-dealkyl metabolite PMA should be responsible for the positive immunoassay results. Using our systematic toxicological analysis procedure, every positive amphetamine immunoassay could be explained by detection of MO-EA, HO-EA, and/or PMA. Misinterpretation of the origin of MO-EA, HO-EA, or PMA can be avoided by detecting the specific (non-dehydroxybutylated) metabolites of MB, which are excreted for a much longer time after ingestion.

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