The pharmacokinetic profile of oxazepam

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.

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.

Sudden death and benzodiazepines

A study of 16 deaths associated with toxic concentrations of benzodiazepines during the period of 5 years leading up to July 1994 is presented. Cases where other drugs, including ethanol, had contributed to the death were excluded. All cases were subject to a full macroscopic and microscopic examination by pathologists, and all cases were subject to a full toxicological work-up. Preexisting natural disease was a feature of 11 cases. In the remaining five cases, death was caused solely by benzodiazepines. There were 14 suicides. Nitrazepam and temazepam were the most prevalent drugs detected, followed by oxazepam and flunitrazepam. Minimum toxic femoral blood concentrations of 7-aminonitrazepam, 7-aminoflunitrazepam, and oxazepam were estimated as 0.5, 0.2, and 2 mg/L, respectively. Relating these deaths to prescription rates in Victoria suggest that flunitrazepam may be inherently more toxic if misused than other benzodiazepines currently available on the Australian market.

Pharmacokinetics of benzodiazepines: metabolic pathways and plasma level profiles

Large differences exist among the various benzodiazepines with regard to their pharmacokinetic properties and metabolism in man. Some are eliminated from the body at a relatively slow rate, e.g. desmethyldiazepam, and others are metabolized rapidly, e.g. midazolam, triazolam. Several benzodiazepines have major active metabolites that are slowly eliminated, e.g. medazepam, halazepam , quazepam and, consequently, should be considered as potentially long-acting. Such differences may be very important clinically because pharmacokinetic data will help to optimize drug therapy with respect to the choice of the proper drug and drug preparation, as well as with the choice of a proper dose and dosage regimen. The therapeutic objectives of drug therapy differ quite considerably for the various clinical indications of benzodiazepines. In anti-anxiety and anti-epileptic therapy, prolonged or continuous treatment is pursued, so that compounds with relatively long or intermediate elimination half-lives of parent drug or active metabolites are of advantage. In hypnotic treatment, on the other hand, the duration of drug action should be restricted to the duration of the night, hence a compound with a short elimination half-life may be preferred. An overview is given of the pharmacokinetics of the major benzodiazepines currently available and of some interesting new ones that are still in the development stage.

Intravenous benzodiazepines as anaesthetic agents: pharmacokinetics and clinical consequences

Despite extensive and numerous pharmacokinetic studies on benzodiazepines, the published pharmacokinetic data do not adequately explain the clinical differences found between different benzodiazepine derivatives after intravenous administration. Especially, correlations between initial drug responses and distributional changes of the benzodiazepines are limited. However, during the elimination phase some relationships exist between the kinetic and dynamic phenomena. Age, sex, diseases and concomitantly given drugs cause clinically important alterations in the pharmacokinetics of benzodiazepines. Generally these anxiolytics and sedatives should be considered as adjuvants to general anaesthesia, but not primarily as routine induction agents. The major reasons for this limitation are a high variability in drug response, a relatively slow onset of action and long-lasting residual effects. However, benzodiazepines have many important advantages (see Table 5) when used as intravenous inducing agents of general anaesthesia.