Lefetamine (N,N-dimethyl-1,2-diphenylethylamine, L-SPA) was marketed as an opioid analgesic in Japan and Italy. After being widely abused, it became a controlled substance. It seems to be a pharmaceutical lead for designer drugs because N-ethyl-1,2-diphenylethylamine (NEDPA) and N-iso-propyl-1,2-diphenylethylamine (NPDPA) were confiscated by the German police. In contrast to these derivatives, metabolism and detectability of lefetamine were not studied yet. Therefore, phase I and II metabolism should be elucidated and correlated to the derivatives. Also the detectability using the authors' standard urine screening approaches (SUSA) needed to be checked. As lefetamine was commercially unavailable, it had to be synthesized first. For metabolism studies, a high dose of lefetamine was administered to rats and the urine samples worked up in different ways. Separation and analysis were achieved by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-high resolution-tandem mass spectrometry (LC-HR-MS/MS). In accordance with NEPDA and NPDPA, the following metabolic steps could be proposed: N-oxidation, N-dealkylation, mono- and bis-hydroxylation of the benzene ring, and hydroxylation of the phenyl ring only after N-dealkylation. The di-hydroxy metabolites were conjugated by methylation of one hydroxy group, and hydroxy metabolites by glucuronidation or sulfation. All initial metabolites could also be detected in human liver preparations. After a therapeutic lefetamine dose, the bis-nor, bis-nor-hydroxy, nor-hydroxy, nor-di-hydroxy metabolites could be detected using the authors' GC-MS SUSA and the nor-hydroxy-glucuronide by the LC-MS(n) SUSA. Thus, an intake of lefetamine should be detectable in human urine assuming similar pharmacokinetics.