Impact of rat P450 genetic polymorphism on diazepam metabolism

Pharmacokinetics of Diazepam and Its Metabolites in Urine of Chinese Participants

BACKGROUND

Urine is conventionally used as a specimen to document diazepam-related crimes; however, few reports have described the pharmacokinetics of diazepam and its metabolites in urine.

OBJECTIVE

This study aimed to investigate the pharmacokinetics of diazepam and its metabolites, including glucuronide compounds, in the urine of Chinese participants.

METHODS

A total of 28 volunteers were recruited and each participant ingested 5 mg of diazepam orally. Ten milliliters of urine were collected from each participant at post-consumption timepoints of prior (zero), 1, 2, 4, 8, 12, and 24 h and 2, 3, 6, 12, and 15 days. All samples were extracted by solid-phase extraction and analyzed using high-performance liquid chromatography-tandem mass spectrometry. Diazepam and its main metabolites, except for temazepam, were detected in the urine of volunteers. Pharmacokinetic parameters were analyzed using the pharmacokinetic software DAS according to the non-compartment model.

RESULTS

Urinary diazepam peaked at 2.38 ng/mL (C_max) and 1.93 h (T_max). The urinary metabolite nordiazepam peaked at 1.17 ng/mL and 100.21 h; temazepam glucuronide (TG) peaked at 145.61 ng/mL and 41.14 h; and oxazepam glucuronide (OG) peaked at 101.57 ng/mL and 165.86 h. The elimination half-life (t_½z) and clearance (CLz/F) for diazepam were 119.58 h and 65.77 L/h, respectively. The t_½z of the metabolites nordiazepam, TG, and OG was 310.58 h, 200.17 h, and 536.44 h, respectively. Finally, this study found that both diazepam and its main metabolites in urine were detectable for at least 15 days, although there were individual differences.

CONCLUSION

The results regarding diazepam pharmacokinetics in urine would be of great help in forensic science and drug screening.

Lack of direct involvement of a diazepam long-term treatment in the occurrence of irreversible cognitive impairment: a pre-clinical approach

Several observational studies have found a link between the long-term use of benzodiazepines and dementia, which remains controversial. Our study was designed to assess (i) whether the long-term use of benzodiazepines, at two different doses, has an irreversible effect on cognition, (ii) and whether there is an age-dependent effect. One hundred and five C57Bl/6 male mice were randomly assigned to the 15 mg/kg/day, the 30 mg/kg/day diazepam-supplemented pellets, or the control group. Each group comprised mice aged 6 or 12 months at the beginning of the experiments and treated for 16 weeks. Two sessions of behavioral assessment were conducted: after 8 weeks of treatment and after treatment completion following a 1-week wash-out period. The mid-treatment test battery included the elevated plus maze test, the Y maze spontaneous alternation test, and the open field test. The post-treatment battery was upgraded with three additional tests: the novel object recognition task, the Barnes maze test, and the touchscreen-based paired-associated learning task. At mid-treatment, working memory was impaired in the 15 mg/kg diazepam group compared to the control group (p = 0.005). No age effect was evidenced. The post-treatment assessment of cognitive functions (working memory, visual recognition memory, spatial reference learning and memory, and visuospatial memory) did not significantly differ between groups. Despite a cognitive impact during treatment, the lack of cognitive impairment after long-term treatment discontinuation suggests that benzodiazepines alone do not cause irreversible deleterious effects on cognitive functions and supports the interest of discontinuation in chronically treated patients.

Designer benzodiazepines versus prescription benzodiazepines: can structural relation predict the next step?

Designer benzodiazepines are a part of the recently discovered abuse synthetic drugs called Novel Psychoactive Substances (NPS) which need to be controlled due to their constantly growing market. Most of them are derived from the medically approved benzodiazepines used nowadays yet, may possess stronger effects, more toxicity, and longer durations of action. Some differences have also been observed in their detection and characteristics, in addition to the variations discovered in postmortem redistribution and drug stability. All these major alterations in features can result from only minor structural modifications. For example, a classic benzodiazepine (BZD) like diazepam only lacks one fluorine atom which exists in its derivatized designer drug, diclazepam, making substantial differences in activity. For this reason, it is essential to study the designer drugs in order to identify their dangers and distinguish them thus rule out their abuse and control the spread of such drugs. This review would highlight the distinct characteristics of some of the most commonly abused designer benzodiazepine analogies in relation to their original prescription BZD compounds.

Primary Human Hepatocyte Spheroid Model as a 3D In Vitro Platform for Metabolism Studies

3D cultures of primary human hepatocytes (PHH) are emerging as a more in vivo-like culture system than previously available hepatic models. This work describes the characterisation of drug metabolism in 3D PHH spheroids. Spheroids were formed from three different donors of PHH and the expression and activities of important cytochrome P450 enzymes (CYP1A2, 2B6, 2C9, 2D6, and 3A4) were maintained for up to 21 days after seeding. The activity of CYP2B6 and 3A4 decreased, while the activity of CYP2C9 and 2D6 increased over time (P < 0.05). For six test compounds, that are metabolised by multiple enzymes, intrinsic clearance (CL_int) values were comparable to standard in vitro hepatic models and successfully predicted in vivo CL_int within 3-fold from observed values for low clearance compounds. Remarkably, the metabolic turnover of these low clearance compounds was reproducibly measured using only 1-3 spheroids, each composed of 2000 cells. Importantly, metabolites identified in the spheroid cultures reproduced the major metabolites observed in vivo, both primary and secondary metabolites were captured. In summary, the 3D PHH spheroid model shows promise to be used in drug discovery projects to study drug metabolism, including unknown mechanisms, over an extended period of time.

Inhibitory Effect of Imperatorin on the Pharmacokinetics of Diazepam In Vitro and In Vivo

Background

Diazepam is a benzodiazepine drug used to treat anxiety, insomnia, and muscle spasms. Imperatorin is a phytochemical isolated from medicinal plants and is widely used in herbal medicine. The aim of this study was to investigate the interactions between imperatorin and diazepam in vitro and in vivo and to provide evidence-based guidance for the safe clinical use of the drug.

Methods

In vitro inhibition of imperatorin was assessed by incubating rat liver microsomes with diazepam to determine IC₅₀ values and the type of inhibition. For in vivo assessment, six rats were pretreated with 50 mg/kg imperatorin for two weeks, six were administered saline, and a single dose of 10 mg/kg diazepam was administered orally to both groups 30 min after the administration of imperatorin.

Results

Imperatorin inhibited the in vitro metabolism of diazepam via the competitive mechanism of CYP450. The IC₅₀ values of imperatorin to nordazepam and temazepam were 1.54 μM and 1.80 μM, respectively. The inhibitory constant values for temazepam and nordazepam were 1.24 μM and 1.29 μM, respectively. Long-term administration of imperatorin significantly increased the AUC_(0-12h), AUC_(0-∞), and Cmax of diazepam, while Vz/F and CLz/F were decreased significantly (P < 0.05). In turn, the AUC_(0-12h), AUC_(0-∞), and Cmax of nordazepam and temazepam decreased significantly, and Vz/F and CLz/F increased significantly (P < 0.05).

Conclusions

This study demonstrates that imperatorin inhibits the metabolism of diazepam both in vitro and in vivo. These results indicated that more attention should be paid when taking diazepam together with food or herbs containing IMP, although further investigation is still needed.

Metabolic profile of oxazepam and related benzodiazepines: clinical and forensic aspects

Anxiolytic drugs, namely benzodiazepines, are the most commonly used psychoactive substances since anxiety disorders are prevalent mental disorders particularly in the Western world. Oxazepam is a short-acting benzodiazepine and one of the most frequently prescribed anxiolytic drugs. It is also the active metabolite of a wide range of other benzodiazepines, such as diazepam, ketazolam, temazepam, chlordiazepoxide, demoxazepam, halazepam, medazepam, prazepam, pinazepam, and chlorazepate. Therefore, relevant clinical and forensic outocomes may arise, namely those related to interference in driving performance. It is clinically available as a racemic formulation, with S-enantiomer being more active than R-enantiomer. In humans, it is mainly polimorphically metabolized by glucuronide conjugation at the 3-carbon hydroxyl group, yielding stable diastereomeric glucuronides (R- and S-oxazepam glucuronide). Relevant metabolic and stereoselective interspecies differences have been reported. In this work, the pharmacokinetics of oxazepam with particular focus on metabolic pathways is fully reviewed. Moreover, the metabolic profile of other prescribed benzodiazepines that produce oxazepam as a metabolite is also discussed. It is aimed that knowing the metabolism of oxazepam and related benzodiazepines may lead to the development of new analytical strategies for its early detection and help in further toxicological and clinical interpretations.

Pharmacodynamic and pharmacokinetic interactions between simvastatin and diazepam in rats

BACKGROUND

Statins and benzodiazepines are widely used drugs, especially in ischemic heart disease, where exacerbation caused by anxiety can even lead to cardiac death. There have not been any reports of statin drug interaction with anxiolytics so far, but it is possible that these drugs interact with each other. We examined the effect of chronic oral administration of simvastatin on the anxiolytic activity and pharmacokinetics of diazepam in rats.

METHODS

Studies were conducted on male Wistar Han rats treated with simvastatin (2.5, 5, 10, 20mg/kg) for 4-6 weeks, and/or diazepam (2.5, 5, 10mg/kg) administered once on the day of the study. Evaluation of potential pharmacodynamic interaction was based on the behavioral tests: elevated plus maze (EPM) test and the Vogel conflict test (VCT). The assessment of the potential pharmacokinetic interaction was based on measurements of concentrations of diazepam and its metabolites in the blood of animals.

RESULTS

Diazepam 5 and 10mg/kg given together with simvastatin 10 and 20mg/kg showed no anxiolytic effect in the EPM test. In the VCT diazepam combinations with simvastatin did not produce any anxiolytic effect either, with an exception of the co-administration of diazepam 10mg/kg and simvastatin 10mg/kg. Simvastatin (20mg/kg) significantly reduced the area under curve (AUC) of diazepam by 51.6% and temazepam by 54.6%.

CONCLUSIONS

Abolition of diazepam anxiolytic effect during concomitant use of simvastatin is probably caused by diminished bioavailability of diazepam, although pharmacodynamic interaction between these drugs cannot be excluded.

The impact of solute carrier (SLC) drug uptake transporter loss in human and rat cryopreserved hepatocytes on clearance predictions

Cryopreserved hepatocytes are often used as a convenient tool in studies of hepatic drug metabolism and disposition. In this study, the expression and activity of drug transporters in human and rat fresh and cryopreserved hepatocytes was investigated. In human cryopreserved hepatocytes, Western blot analysis indicated that protein expression of the drug uptake transporters [human Na(+)-taurocholate cotransporting polypeptide (NTCP), human organic anion transporting polypeptides (OATPs), human organic anion transporters, and human organic cation transporters (OCTs)] was considerably reduced compared with liver tissue. In rat cryopreserved cells, the same trend was observed but to a lesser extent. Several rat transporters were reduced as a result of both isolation and cryopreservation procedures. Immunofluorescence showed that a large portion of remaining human OATP1B1 and OATP1B3 transporters were internalized in human cryopreserved hepatocytes. Measuring uptake activity using known substrates of OATPs, OCTs, and NTCP showed decreased activity in cryopreserved as compared with fresh hepatocytes in both species. The reduced uptake in cryopreserved hepatocytes limited the in vitro metabolism of several AstraZeneca compounds. A retrospective analysis of clearance predictions of AstraZeneca compounds suggested systematic lower clearance predicted using metabolic stability data from human cryopreserved hepatocytes compared with human liver microsomes. This observation is consistent with a loss of drug uptake transporters in cryopreserved hepatocytes. In contrast, the predicted metabolic clearance from fresh rat hepatocytes was consistently higher than those predicted from liver microsomes, consistent with retention of uptake transporters. The uptake transporters, which are decreased in cryopreserved hepatocytes, may be rate-limiting for the metabolism of the compounds and thus be one explanation for underpredictions of in vivo metabolic clearance from cryopreserved hepatocytes.