ABSTRACT
Both chlormezanone enantiomers, for the first time obtained by enantiospecific HPLC with a 100% yield, bind to oxidized cytochrome P-450 in rat liver microsomes with a binding curve according to type I, similar to hexobarbital but less pronounced. There are no differences between the binding curves of the two enantiomers. Ethylmorphine N-demethylation, ethoxycoumarin and ethoxyresorufin O-deethylation are inhibited by both chlormezanone enantiomers at 0.1-1 mM concentrations: no differences could be found. Luminol and lucigenin amplified chemiluminescence indicating the formation of reactive oxygen species was not influenced by either enantiomer in concentration ranges between millimolar and micromolar, whereas hydrogen peroxide formation was inhibited. NADPH/Fe stimulated lipid peroxidation was not influenced. Scavenger activity could not be demonstrated: the zymosan stimulated whole blood chemiluminescence was not influenced significantly.
Subject(s)
Chlormezanone/metabolism , Cytochrome P-450 Enzyme System/metabolism , Microsomes, Liver/metabolism , Muscle Relaxants, Central/metabolism , Acridines/chemistry , Analgesics, Opioid/metabolism , Animals , Anticoagulants/metabolism , Chromatography, High Pressure Liquid , Coumarins/metabolism , Ethylmorphine/metabolism , Hydrogen Peroxide/metabolism , Indicators and Reagents/chemistry , Lipid Peroxidation/drug effects , Luminescent Measurements , Luminol/chemistry , Male , Oxazines/metabolism , Protein Binding , Rats , Reactive Oxygen Species/metabolism , Stereoisomerism , Zymosan/chemistryABSTRACT
Chlormezanone binds to oxidized cytochrome P450 in rat liver microsomes with a binding curve according to type I like hexobarbital but less pronounced and with a general shift to the left. Ethylmorphine N-demethylation, ethoxycoumarin and ethoxyresorufin O-deethylation are inhibited by chlormezanone in mM concentrations only whereas pentoxyresorufin O-depentylation is inhibited by about 50% in microM concentrations. Luminol and lucigenin amplified chemiluminescence indicating the formation of reactive oxygen species was not influenced in concentration ranges between mM and microM, whereas NADPH/Fe stimulated lipid peroxidation showed a tendency of inhibition. But scavenger activity could not be demonstrated: the zymosan stimulated chemiluminescence of whole blood was not influenced significantly. The degradation process of chlormezanone was elucidated. The first step involves ring opening by chemical hydrolysis with subsequent formation of an unstable acylhalfaminal which is the source of 4-chlorobenzaldehyde. This aldehyde undergoes enzymatically controlled oxidation to 4-chlorobenzoic acid which is the parent compound of following phase II reactions. The second degradation product is 2-carboxyethane-sulfinic-acid-N-methylamide, which is hydrolyzed very quickly. Neither oxidation of the sulfinic acid or its N-methylamide derivative could be observed nor N-demethylation of chlormezanone.
Subject(s)
Chlormezanone/metabolism , Chlormezanone/pharmacology , Microsomes, Liver/drug effects , Microsomes, Liver/metabolism , Muscle Relaxants, Central/metabolism , Muscle Relaxants, Central/pharmacology , Animals , Biotransformation , Coumarins/metabolism , Cytochrome P-450 Enzyme Inhibitors , Cytochrome P-450 Enzyme System/metabolism , Drug Interactions , Ethylmorphine/metabolism , Lipid Peroxidation/drug effects , Luminescent Measurements , Male , Microsomes, Liver/enzymology , Oxazines/metabolism , Oxygenases/antagonists & inhibitors , Rats , Rats, Wistar , Reactive Oxygen Species/metabolism , Stimulation, Chemical , Zymosan/pharmacologyABSTRACT
The metabolism of chlormezanone (Muskel Trancopal) in man was studied by the aid of gas chromatography/mass spectrometry and high performance liquid chromatography after an oral dose of 400 mg. Six metabolites and/or degradation products were identified in the urine. Some of the metabolites are formed at least partially by nonenzymatic hydrolysis in the stomach. In contrast to previous publications, no unchanged drug was detected in plasma and urine. The main metabolite in plasma is generated by cleavage of the amide bond in the six-membered heterocyclic ring. This derivative is easily formed by in vitro hydrolysis at pH 1, too. It structurally resembles baclofene. About 40% of the dose is excreted with the urine. The major metabolite in urine is 4-chlorohippuric acid. Additionally, 4-chloro-benzoyl-N-methylamide, 4-chlorobenzoic acid, N-methylimino-4-chlorobenzaldehyde, 4-chlorobenzaldehyde, and "hydrolized" chlormezanone were identified.
Subject(s)
Chlormezanone/metabolism , Biotransformation , Chlormezanone/blood , Chlormezanone/urine , Gas Chromatography-Mass Spectrometry , HumansABSTRACT
A sensitive and selective determination method of chlormezanone in plasma has been divised. Chlormezanone in plasma was extracted with toluene at pH 4.5, and converted into p-chlorobenzaldehyde in 0.1 N NaOH. Using p-bromobenzaldehyde as an internal standard, the hydrolysis product and the internal standard were extracted with n-hexane, and the extract was concentrated in vacuo in the presence of isoamyl alcohol to prepare the sample solution. The sample solution was submitted to electron-capture gas chromatography. Chlormezanone was determined by use of the peak height ratio of p-chlorobenzaldehyde against the internal standard. The method was utilized successfully for pharmacokinetic studies of chlormezanone in plasma.
Subject(s)
Chlormezanone/blood , Benzaldehydes/metabolism , Chlormezanone/metabolism , Chlormezanone/pharmacology , Gas Chromatography-Mass Spectrometry/methods , Humans , Male , Time FactorsABSTRACT
1. After oral administration of [14C]chlormezanone, about 74% of the dose was excreted into the urine of rats within 24 h and 21% into urine of mice within 2 h. 2. Biliary excretion of radioactivity was about 10% of the dose in rats. 3. Six metabolites in the urine of rats and mice were identified as p-chlorobenzoic acid, p-chlorohippuric acid, N-methyl-p-chlorobenzamide, 2-[N-methyl-N-(p-chlorobenzoyl)]carbamoylethylsulphonic acid, 3-sulphopropionic acid and the glucuronide of p-chlorobenzoid acid. 4. The effect of combination with aspirin on the metabolic fate of chlormezanone was investigated in rats and mice. Aspirin had no effect on the metabolite pattern in either species but reduced the rate of excretion, particularly in the mouse.
