Oxazepam metabolite

The stability of diazepam and its metabolites (oxazepam, temazepam, and demeth-yldiazepam) when present in liver of treated bulls has been studied (108). Following boiling in water for 1 h, the oxazepam metabolite was the most unstable of the compounds studied, being degraded to an extent of approximately 50%. The parent drug and the other metabolites were more stable they were all present, after treatment, at levels corresponding to 79-89% of the initial concentrations. 

Signs and symptoms of BZ withdrawal are similar to those of alcohol withdrawal, including muscle pain, anxiety, restlessness, confusion, irritability, hallucinations, delirium, seizures, and cardiovascular collapse. Withdrawal from short-acting BZs (e.g., oxazepam, lorazepani, alprazolam) has an onset within 12 to 24 hours of the last dose. Diazepam, chlordiazep-oxide, and clorazepate have elimination half-lives (or active metabolites with elimination half-lives) of 24 to greater than 100 hours. So, withdrawal may be delayed for several days after their discontinuation. 

For plasma and blood experiments, LC effluent was directed to waste for the first 1 min. Conventional blood analysis by drawing 1 mL samples from the saphenous catheter was used to validate SPME results. These samples were subjected to PPT with acetonitrile and the supernatant from centrifugation was analyzed. The SPME probes were also evaluated for pharmacokinetic analysis of diazepam and its metabolites, oxazepam and nordiazepam. Good correlation was obtained for conventional blood drawn from saphenous and cephalic sites of the animals, as shown in Figure 1.48. Although the analytical parameters for the automated study need improvement, the authors cite the study as a first demonstration of SPME technology for in vivo analysis. 

Diazepam and its nordiazepam, oxazepam, and temazepam metabolites are well retained by the MIP, while they are much less retained on NIP, also exhibiting large RSD. Other benzodiazepines of similar structures (Figure 1.50) were well retained on the MIP, showing that this template can be used for the general class of benzodiazepines. Two benzodiazepines studied, chlordiazepoxide and flunitrazepam, were poorly retained, indicating poor fit of these structures into the templated MIP. 

While comparatively few dihydrodiols have been observed in the metabolism of phenyl-containing drugs, the examples above are far from unique. Thus, oxazepam incubated in rat, mouse, and human microsomes did yield a dihydrodiol besides the para-phenol [82], A more-recent example is that of rofecoxib (10.22), a potent and selective cyclooxygenase-2 (COX-2) inhibitor. In rats and dogs, phenyl oxidation produced 4 -hydroxyrofecoxib and rof-ecoxib-3, 4 -dihydrodiol as urinary metabolites of intermediate quantitative importance [83]. 

In the presence of cirrhosis or other liver impairment, lorazepam or oxazepam should be utilized for detoxification. These two benzodiazepines have no active hepatic metabolites and are generally considered safer choices for patients with liver damage. Once the starting point for the taper is determined, the dose is decreased by 10-20% per day. It is important to note that this rate of taper is much faster than that used for patients treated chronically with benzodiazepines who are discontinuing their anxiolytic in order to determine if it is still needed for control of symptoms. In that case, the rate of decrease is 10-20% per week. Should the patient display... 

By virtue of their long half-lives, diazepam (ti/2 - 32 h) and, still more so, its metabolite, nordazepam (ti/2 50-90 h), are eliminated slowly and accumulate during repeated intake. Oxazepam undergoes conjugation to glucuronic acid via its hydroxyl group (ti/2 = 8 h) and renal excretion (A). 

Diazepam, oxazepam, and N-desmethyldiazepam have been determined under isocratic conditions (342) a somewhat more sensitive assay for diazepam and N-methyldiazepam has been reported (545). The closely related compounds, chlordiazepoxide and its N-demethyl metabolite, have also been determined (344). Analysis of the antidepressant amitriptyline, its metabolites and related drugs have been carried out using a four-component solvent (345, 346) and also aqueous acetonitrile (547). 

Eight BDZs among the most frequently encountered in forensic toxicology (clonazepam, desal-kylflurazepam, diazepam, flunitrazepam, lorazepam, midazolam, nordiazepam and oxazepam) were determined in whole blood after solvent extraction with butyl chloride and fast isocratic separation using a C18 (100 x 4.6 mm x 5 (tm) column [61]. The mobile phase was composed of phosphate buffer (35mM, pH 2.1) and acetonitrile (70 30, v/v) and the flow rate was 2mL/min. Within less than 4 min of analysis time, the analytes could be successfully determined starting from therapeutic concentrations. Using HPLC coupled with APCI-MS-MS, Rivera et al. [62] set up a method for the detection of 18 BDZ and metabolites after butyl chloride extraction at alkaline pH in 0.5mL... 

Discontinuation of a hypnotic after a month of continued use can cause a rebound of REM (rapid eye movement) sleep. The duration of action of a hypnotic is determined not only by the half-life of the mother substance but especially by their biological half-life determined by the half-life of the mother substance and the biological active metabolites. On this basis the benzodiazepines can be divided in four different groups ultra short-acting with a half-life < 6 hours such as midazolam and triazolam, short-acting with half-lives between 6 and 12 hours like lormetazepam, loprazolam, oxazepam and temazepam. Alprazolam, bromazepam... 

The metabolism of some benzodiazepines. In some cases, several active metabolites are formed. A result Is very long apparent half-lives. In many cases, the ultimate product is oxazepam. Active metabolic product. 

Knowing the structure of a particular BZ drug can help predict the metabolic pathway for that drug. For example, oxazepam, lorazepam, and temazepam are all 3-OH BZs and are directly conjugated (Chouinard et ah, 1999). Temazepam is partly demethylated to oxazepam, but otherwise these drugs have no active metabolites (Bellantuono et ah, 1980). 

Unlike oxidized BZDs, conjugated BZDs (e.g., lorazepam, lormetazepam, oxazepam, and temazepam) do not have active metabolites. Only the parent compounds account for clinical activity. 

Benzodiazepines undergo extensive and complex metabolism. They are excreted mainly in the urine, largely in the form of several metabolites. Biotransformation processes include mainly hydroxylation and A-dealkylation reactions, whereas the end-products include both free and conjugated compounds (116). Chlordiazepoxide, for example, is metabolized to oxazepam and other metabolites and, depending on its dosage, urine may contain significant concentrations of oxazepam (117). 

Polarographic methods have been extremely useful for the determination of the urinary excretion of the 1,4-benzodiazepines. An assay that employs selective solvent extraction and acid hydrolysis of diazepam and its major metabolites, iV-desmethyldiazepam and oxazepam, to their respective benzophe-nones has been employed to measure the urinary excretion of diazepam [183]. A pulse polarographic assay has been reported that will measure the urinary excretion of bromazepam following a single 12-mg dose [184]. The assay employs selective extraction of bromazepam and the 2-amino-5-bromobenzoyl-pyridine metabolite from the deconjugated metabolites, 3-hydroxybromazepam and 2-amino-3-hydroxy-5-bromobenzoylpyridine, into separate diethyl ether fractions. The residues of the respective extracts are dissolved in phosphate buffer (pH 5.4) and analyzed by pulse polarography, which yields two distinct... 

Diazepam undergoes N- de me thy 1 ation to an active metabolite, nordiazepam. Both of these compounds are then hydroxylated to temazepam and oxazepam, respectively. These metabolites are also active, but are usually rapidly excreted and do not accumulate in plasma. Only small... 

The rates of oral absorption of benzodiazepines differ depending on a number of factors, including lipophilicity. Oral absorption of triazolam is extremely rapid, and that of diazepam and the active metabolite of clorazepate is more rapid than other commonly used benzodiazepines. Clorazepate is converted to its active form, desmethyldiazepam (nordiazepam), by acid hydrolysis in the stomach. Oxazepam, lorazepam, and temazepam are absorbed from the gut at slower rates than other benzodiazepines. The bioavailability of several benzodiazepines, including chlordiazepoxide and diazepam, may be unreliable after intramuscular injection. Most of the barbiturates and other older sedative-hypnotics are absorbed rapidly into the blood following their oral administration. 

The formation of active metabolites has complicated studies on the pharmacokinetics of the benzodiazepines in humans because the elimination half-life of the parent drug may have little relationship to the time course of pharmacologic effects. Those benzodiazepines for which the parent drug or active metabolites have long half-lives are more likely to cause cumulative effects with multiple doses. Cumulative and residual effects such as excessive drowsiness appear to be less of a problem with such drugs as estazolam, oxazepam, and lorazepam, which have shorter half-lives and are metabolized directly to inactive glucuronides. Some pharmacokinetic properties of selected benzodiazepines are listed in Table 22-1. 

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