Oxidative behaviour of apomorphine and its metabolites.

The metabolism of apomorphine is quite complex due to interactions with proteins and other tissue components that affect its pharmacokinetic profile. The electrochemical oxidation mechanism of apomorphine and of some synthesised apomorphine derivatives was studied. It was found to be related to the reaction of o-diphenol and tertiary amine groups and strongly dependent on pH.     

Superoxide anion scavenging properties of fluvastatin and its metabolites.

We investigated the in vitro superoxide anion scavenging activities of fluvastatin and its metabolites. Fluvastatin showed dose-dependent superoxide anion scavenging activity in the NADH/phenazine methosulphate (PMS)/nitroblue tetrazolium (NBT) system, and the effect was as potent as the reference antioxidant, trolox, which is a water-soluble alpha-tocopherol derivative. The superoxide anion scavenging activities of the major metabolites of fluvastatin (M2, M3, M4, M7) were also determined in this system. All of these metabolites showed the activity. In particular, M2 and M3, which possess a phenolic hydroxyl group at the 5 or 6-position of the indole moiety, respectively, showed 3 times stronger activities than that of fluvastatin. Further, we also determined the effects of fluvastatin, M2 and M3 on phorbol myristate acetate (PMA)-induced superoxide anion generation in human peripheral blood polymorphonuclear leukocytes (PMN). The compounds tested also showed a depressing effect on the amount of superoxide anion in this system. We suggest that fluvastatin and its metabolites have the potential to protect cells or lipids from oxidative modification mediated by superoxide anion.     

Simultaneous determination of nefiracetam and its metabolites by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic assay was developed to simultaneously quantitate nefiracetam (NEF), a novel nootropic agent, and its three known oxidized metabolites (N-[(2,6-dimethylphenylcarbamoyl)methyl]succinamic acid (5-COOH-NEF), 4-hydroxy-NEF and 5-hydroxy-NEF) in human serum and urine. The quantitative procedure was based on solid-phase extraction with Sep-Pak C18 and ultraviolet detection at 210 nm. The calibration curves of NEF and the metabolites were linear over a wide range of concentrations (0.5-21.5 nmol/ml for NEF and 0.4-9.5 nmol/ml for metabolites in serum and 4-86 nmol/ml for NEF and 8-190 nmol/ml for metabolites in urine). Intra- and inter-day assay coefficients of variation for the compounds were less than 10%. The limit of detection was 0.1 nmol/ml for NEF, 5-COOH-NEF and 4-hydroxy-NEF, and 0.2 nmol/ml for 5-hydroxy-NEF in both serum and urine. This method is applicable for the determination of NEF and its metabolites in human serum and urine with satisfactory accuracy and precision.     

Quantitation of chlordiazepoxide and its metabolites in biological fluids by thin-layer chromatography.

Chlordiazepoxide and its 4 major metabolites were assayed after separation by thin-layer chromatography following extraction from biological fluids. The compounds become intensely fluorescent in the presence of red, fuming nitric acid. The resulting compounds are quantitated with a spectrodensitometer with a fluorescent attachment. The sensitivity varies between 0.05 and 0.1 microgram. The coefficient of variation is 1.4% for assays in urine and 6.4% in serum.     

High-performance liquid chromatography-electrochemical detection of vecuronium and its metabolites in human plasma.

A high-performance liquid chromatographic assay coupled with electrochemical detection has been developed for the determination of vecuronium and its three putative deacetylated metabolites in human plasma. A novel solid-phase extraction procedure allowed good recovery of both vecuronium and its metabolites, together with ease and speed of execution. This method was sensitive, reproducible and accurate over the therapeutic range of concentrations of vecuronium and its metabolites, and was applied successfully to a study of the pharmacokinetics of vecuronium in anaesthetized patients.     

Studies on the determination of chlorotestosterone and its metabolites in bovine urine.

Chlorotestosterone and its metabolites were determined in urine samples from bovine animals treated with chlorotestosterone acetate by oral and intramuscular routes. Sample preparation, involving enzymatic deconjugation and solid-phase extraction, was optimised. The effect of different enzyme preparations, pH, and time of incubation were studied. An extraction/clean-up procedure based on solid-phase extraction (C18 cartridge) and liquid-liquid clean-up was developed. Determination of chlorotestosterone and its metabolites was by enzyme immunoassay and GC-MS. Metabolites were converted into their TMS-enol-TMS-ether and TMS-oxime-TMS-ether forms before GC-MS (EI) analysis.     

Antihormonal agents. Part 1: HPLC of RU 38486 and its metabolites

Procedures are described for the TLC and reverse phase HPLC analysis of the antihormonal steroid RU 38486 and its metabolites. Conditions are developed for the HPLC of the pure drug substance and a tablet formulation, and also for following its pharmacokinetics and metabolism.     

Analysis of methamphetamine and its metabolites in hair

Methamphetamine (MA) is a sympathomimetic amine whose abuse has become a serious problem in Japan, Korea, Taiwan and other Southeast Asian countries. The use of hair for the determination of MA use has become more commonplace. The maximum period in which MA and its main metabolites (amphetamine and p-hydroxymethamphetamine) can be detected in urine is about 10 days after its use. However, proof of MA use is possible in hair even several years after its use if the part of the hair that grew in the period of its use is available. In addition, segmental analysis of hair is capable of clarifying the history of MA abuse. This paper reviews the clean-up, extraction, analytical method and distribution of MA and its metabolites in hair from reports published in the last 20 years.     

Radical scavenging properties of nicotinamide and its metabolites

By means of pulse radiolysis the reactivity of nicotinamide, its metabolites and selected pyridinium salts towards reactive oxygen species was tested and compared with the pharmacological efficacy of this group of compounds. It was found that pyridinium salts are poor radical scavengers but the positive charge distribution enhances their interactions with immobilized heparin. Thus, superior pharmacological efficacy of 1-methylnicotinamide may be related to its ability to interact with biological tissues rather than to its direct anti-oxidant properties.     

Nonaqueous capillary electrophoresis of dextromethorphan and its metabolites

This study deals with the nonaqueous capillary electrophoretic separation of dextromethorphan and its metabolites using a methanolic background electrolyte. The optimization of separation conditions was performed in terms of the resolution of dextromethorphan and dextrorphan and the effect of separation temperature, voltage, and the characteristics of the background electrolyte were studied. Complete separation of all analytes was achieved in 40 mM ammonium acetate dissolved in methanol. Hydrodynamic injection was performed at 3 kPa for 4 s. The separation voltage was 20 kV accompanied by a low electric current. The ultraviolet detection was performed at 214 nm, the temperature of the capillary was 25°C. These conditions enabled the separation of four analytes plus the internal standard within 9 min. Further, the developed method was validated in terms of linearity, sensitivity, and repeatability. Rat liver perfusate samples were subjected to the nonaqueous capillary electrophoretic method to illustrate its applicability.