Metabolism of levomepromazine in man

The phenothiazine drug, levomepromazine (LM), is used in the treatment of psychiatric disorders and as an analgesic. A single 50 or 100 mg dose of LM was given to healthy male volunteers, and urine samples were collected for 24 h. The urine was treated with beta-glucuronidase, purified by solid-phase extraction, and analyzed on a GC-MS system for identification of LM metabolites. Mass spectra suggesting 14 different LM metabolites were obtained from the samples. Our of these, 13 spectra could be ascribed to specific metabolites, 5 of which have not previously been identified. All these 5 metabolites were hydroxylated at the phenothiazine nucleus. Although the applied method did not determine the positions of hydroxyl groups on phenothiazine nuclei. 3 of the 5 metabolites were identified as O-desmethyl 3-hydroxy LM, O-desmethyl 7-hydroxy LM, and N,O-didesmethyl 7-hydroxy LM, based on their chromatographic properties. In addition two metabolites, one being hydroxylated on the phenothiazine nucleus, and one being O-demethylated and hydroxylated on the nucleus, were found. It is suggested that these were 8-hydroxy LM and O-desmethyl 8-hydroxy LM. The concentrations of 3-hydroxy LM (free+conjugated) appeared to be much higher than the concentrations of any other metabolite in the samples.