Improved high-performance liquid chromatographic method for the determination of ethylmorphine and its metabolites in microsomal incubations and cell culture media

Synthesis, characterization, method development, and validation of nor-ethylmorphine hydrochloride reference material using established analytical techniques for dope control analysis

Ethylmorphine is permitted internationally for therapeutic purposes where morphine is not indicated across the globe. Nor-ethylmorphine a major metabolite of ethylmorphine. To differentiate the intake of morphine from ethylmorphine, nor-ethylmorphine stable reference material is desirable. There is no available commercial source and no data for reference material context for this substance. Therefore, nor-ethylmorphine HCl was synthesized and characterized, and purity and potency were assessed using nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TGA), and high-performance liquid chromatography (HPLC). Purity and potency were found to be 98.29% and 96.40%, respectively, providing a fit for purpose reference material for doping control analysis in sports.

Highly Miniaturized Formats for In Vitro Drug Metabolism Assays Using Vivid® Fluorescent Substrates and Recombinant Human Cytochrome P450 Enzymes

Highly miniaturized P450 screening assays designed to enable facile analysis of P450 drug interactions in a 1536-well plate format with the principal human cytochrome P450 enzymes (CYP3A4, 2D6, 2C9, 2C19, and 1A2) and Vivid® fluorogenic substrates were developed. The detailed characterization of the assays included stability, homogeneity, and reproducibility of the recombinant P450 enzymes and the kinetic parameters of their reactions with Vivid® fluorogenic substrates, with a focus on the specific characteristics of each component that enable screening in a low-volume 1536-well plate assay format. The screening assays were applied for the assessment of individual cytochrome P450 inhibition profiles with a panel of selected assay modifiers, including isozyme-specific substrates and inhibitors. IC50values obtained for the modifiers in 96- and 1536-well plate formats were similar and comparable with values obtained in assays with conventional substrates. An overall examination of the 1536-well assay statistics, such as signal-to-background ratio and Z′ factor, demonstrated that these assays are a robust, successful, and reliable tool to screen for cytochrome P450 metabolism and inhibition in an ultra-high-throughput screening format. ( Journal of Biomolecular Screening 2005:56-66)

Determination of 6-monoacetylmorphine and morphine in plasma, whole blood and urine using high-performance liquid chromatography with electrochemical detection

6-Monoacetylmorphine and morphine were determined simultaneously in plasma, whole blood and urine, after solid-phase extraction, by high-performance liquid chromatography using amperometric detection at 600 mV oxidation potential. The recoveries ranged from 92 to 99%. The reproducibility study indicated that the coefficients of variation were less than 11% for morphine and 12.4% for 6-monoacetylmorphine. The determination limits were 1 ng/ml for morphine and 4 ng/ml for 6-monoacetylmorphine. The method had a good selectivity towards opiate and nonopiate analgesics and other drugs. The stability of the analytes in methanol (standard solutions), in samples (plasma, whole blood and urine) at -20 degrees C and at 20 degrees C, and in samples after enzymatic hydrolysis at 37 degrees C, was also studied. For sample containing 6-monoacetylmorphine, inadequate storage or hydrolysis could lead to overestimation of morphine or its conjugates. The technique described can be applied for the study of the pharmacokinetics of heroin; it is also available for forensic toxicology to distinguish heroin use from medical prescription of morphine and other opiate drugs.

Applicability of cultured hepatocytes derived from goat, sheep and cattle in comparative drug metabolism studies

1. Using trimethoprim (TMP), scoparone (SCOP), ethylmorphine (EtM), 1-naphthol (1-N) and phenol red (PhR) as test substrates, biotransformation activities were investigated in cultured hepatocytes from male and female rat, male and female goat, and female sheep and cattle. 2. As compared with rat hepatocytes, the total culture cytochrome P450 content was relatively well maintained in ruminant hepatocytes. In 72 h, it decreased to approximately half the initial content, whereas in rat hepatocytes only 30% was maintained. In ruminant hepatocytes, sulphation of 1-N remained fairly stable, glucuronidation of PhR decreased gradually, and glucuronidation of 1-N increased during the 72-h culture period. 3. Oxidative metabolism of TMP was rapid in goat and sheep hepatocytes, as compared with rat hepatocytes, reflecting species differences in TMP pharmacokinetics in vivo. In contrast with rat hepatocytes, 6-O-demethylation was by far the major pathway of scoparone metabolism in ruminant hepatocytes. The glucuronidation and sulphation activities were similar among the species. 4. In goat liver cells, sex differences in some oxidative biotransformations were observed, females being more active than males. In rat hepatocytes, a reverse sex difference was observed. 5. In conclusion, cultured hepatocytes from agricultural target species appear a useful in vitro model to study comparative metabolism of veterinary drugs and other xenobiotics. Comparing rat and ruminant, sex and species differences and similarities in drug metabolism can be observed that reflect the in vivo situation.

Cytochrome P450 induction and metabolism of alkoxyresorufins, ethylmorphine and testosterone in cultured hepatocytes from goats, sheep and cattle

Very little is known of cytochrome P450 (P450) patterns and enzyme characteristics in food-producing animal species. Oxidative metabolism of alkoxyresorufins, ethylmorphine (EtM) and testosterone (TST) was used to monitor the effects of the P450 inducers phenobarbital (PB), beta-naphthoflavone (BNF), dexamethasone (DEX) and triacetyloleandomycin (TAO) in primary cultured hepatocytes from goats, sheep and cattle. BNF effectively and specifically induced ethoxyresorufin deethylase (> 20-fold), indicating the presence of an inducible P450 1A form, and down-regulated EtM demethylation and most selected TST hydroxylations. In non-induced hepatocyte cultures, TST was metabolized to 6 beta-, 2 beta-, 12 beta-, and 11 alpha-hydroxy-TST (OHT). PB and, to a lesser extent, DEX non-specifically induced all OHT formations, and EtM demethylation. TAO almost completely inhibited OHT formation and EtM demethylation. These results indicate the involvement of principally one P450 form, or a restricted number of related P450 forms, presumably belonging to the P450 3A subfamily. In western blot analysis, cross reactivity was found with rat anti-P450 3A1 and anti-sheep P450 3A. A more specific PB effect was observed for 16 alpha-OHT, which may be formed though a ruminant P450 2B form. None of the inducers influenced pentoxyresorufin depentylase (PROD) or EtM O-deethylation. Metabolite patterns and inducibility of selected activities in ruminant hepatocytes are in accordance with previous findings in goats in vivo. Cytochrome P450 characteristics in ruminants appear to differ from those in rats whereas similarities to the situation in humans appear to exist.

Hepatic cytochrome P450 induction in goats. Effects of model inducers on the metabolism of alkoxyresorufins, testosterone and ethylmorphine, and on apoprotein and mRNA levels

Male and female African dwarf goats were treated orally with phenobarbital (PB) or triacetyloleandomycin (TAO), or subcutaneously with beta-naphthoflavone (BNF). Hepatic microsomal cytochrome P450 content was increased by PB and TAO, but not by BNF. PB effects on P450 activities were non-selective: ethoxyresorufin deethylase (EROD) and pentoxyresorufin depentylase (PROD), hydroxylation of testosterone (TST) and demethylation of ethylmorphine (ETM) were all induced by a factor of 2-3. A similar non-selective induction was observed with TAO, except for EROD and PROD (no effects). After PB and TAO treatment, increased levels of a protein cross-reactive with anti-sheep P450 3A and 2B were found. Thus, in dwarf goats, both PB and TAO appeared to be P450 3A inducers. Selective PB effects related to a P450 2B form on PROD are lacking but 16 alpha-hydroxylation of TST was induced markedly. At the mRNA level, PB induced an mRNA that showed good sequence homology with a human P450 3A4 cDNA probe, rather than with a rat 3A1 probe. BNF selectively induced EROD, whereas TST hydroxylation and ETM dealkylation were inhibited. With BNF-treated animals, increased concentrations of a protein cross-reactive with anti-rat P450 1A1/1A2 and of an mRNA that showed homology with a human 1A1 cDNA probe, but not with a mouse 1A1/1A2 probe, were observed.