Clinical pharmacokinetics of benzodiazipines

Prescription patterns of benzodiazepines in the Lebanese adult population: a cross-sectional study

This study assessed the profile of benzodiazepine (BDZ) users in Lebanon. Adult patients visiting the pharmacies with prescriptions of BDZs were included in the study. Seven hundred and eighty-six current BDZ users were included, of whom 54.2% were females. Twenty-three percent reported being alcohol consumers and were mostly males. The two most commonly used BDZs were alprazolam (34.6%) and bromazepam (33.6%). The indication for use was mainly anxiety (44.4%), insomnia (22.5%), and depression (15.9%). The prescribing physicians were primarily psychiatrists (43.2%), followed by general practitioners (29.7%). Forty percent had been taking the drug for more than a year. Among those using BDZs for at least 1 month, 35.5% increased the dose with time. Thirty-three percent reported having experienced side effects. Eighteen patients (2.3%) reported taking more than one BDZ concomitantly, while 18.3% were taking drugs that should not be prescribed along with BDZs. In conclusion, the use of BDZs is highest among females, especially for the treatment of anxiety. Moreover, continuous use of the drugs for more than a year as well as significant potential drug interactions was identified.

The behavioral pharmacology of zolpidem: evidence for the functional significance of α1-containing GABA(A) receptors

RATIONALE

Zolpidem is a positive allosteric modulator of γ-aminobutyric acid (GABA) with preferential binding affinity and efficacy for α1-subunit containing GABA(A) receptors (α1-GABA(A)Rs). Over the last three decades, a variety of animal models and experimental procedures have been used in an attempt to relate the behavioral profile of zolpidem and classic benzodiazepines (BZs) to their interaction with α1-GABA(A)Rs.

OBJECTIVES

This paper reviews the results of rodent and non-human primate studies that have evaluated the effects of zolpidem on motor behaviors, anxiety, memory, food and fluid intake, and electroencephalogram (EEG) sleep patterns. Also included are studies that examined zolpidem's discriminative, reinforcing, and anticonvulsant effects as well as behavioral signs of tolerance and withdrawal.

RESULTS

The literature reviewed indicates that α1-GABA(A)Rs play a principle role in mediating the hypothermic, ataxic-like, locomotor- and memory-impairing effects of zolpidem and BZs. Evidence also suggests that α1-GABA(A)Rs play partial roles in the hypnotic, EEG sleep, anticonvulsant effects, and anxiolytic-like of zolpidem and diazepam. These studies also indicate that α1-GABA(A)Rs play a more prominent role in mediating the discriminative stimulus, reinforcing, hyperphagic, and withdrawal effects of zolpidem and BZs in primates than in rodents.

CONCLUSIONS

The psychopharmacological data from both rodents and non-human primates suggest that zolpidem has a unique pharmacological profile when compared with classic BZs. The literature reviewed here provides an important framework for studying the role of different GABA(A)R subtypes in the behavioral effects of BZ-type drugs and helps guide the development of new pharmaceutical agents for disorders currently treated with BZ-type drugs.

Pharmacokinetic evaluation of intranasally administered vinyl polymer-coated lorazepam microparticles in rabbits

The intranasal (IN) administration of lorazepam is desirable in order to maximize speed of onset and minimise carry-over sedation; however, this benzodiazepine is prone to chemical hydrolysis and poor airway retention, and thus, innovative epithelial presentation is required. The aim of this study was to understand how the in situ self-assembly of a mucoretentive delivery system, formed by the dissolution of vinyl polymer-coated microparticles in the nasal mucosa, would influence lorazepam pharmacokinetics (PK). IN administration of the uncoated lorazepam powder (particle size, 6.7 ± 0.1 μm) generated a biphasic PK profile, which was indicative of sequential intranasal and oral absorption (n = 6; dose, 5 mg/kg). Coating the drug with the vinyl polymer, MP1 (9.9 ± 0.5 μm with 38.8 ± 14.0%, w/w lorazepam) and MP2 (10.7 ± 0.1 μm with 47.0 ± 1.0%, w/w lorazepam), allowed rapid systemic absorption (MP1, T (max) 14.2 ± 4.9 min; MP2, T (max) 9.3 ± 3.8 min) in rabbits and modified the PK profiles in a manner that suggested successful nasal retention. The poly(vinyl pyrrolidone)-rich MP2 system provided the best comparative bioavailability, it prolonged the early-phase nasal drug absorption and minimised drug mucociliary clearance, which correlated well with the intermolecular hydrogen-bond-driven vinyl polymer interactions observed in vitro.

Sedation and analgesia usage in severe pandemic H1N1 (2009) infection: a comparison to respiratory failure secondary to other infectious pneumonias

BACKGROUND

During the 2009 H1N1 pandemic (pH1N1), patients requiring mechanical ventilation for respiratory failure received high doses of sedation and analgesia.

OBJECTIVE

To examine sedation and analgesia use among patients with respiratory failure due to severe pH1N1 infection compared to other infectious pneumonias.

METHODS

In this observational cohort study of intensive care unit (ICU) patients with respiratory failure, we compared doses of sedatives and analgesics administered to patients with pH1N1, non-pH1N1 viral pneumonia, and adult respiratory distress syndrome (ARDS) secondary to bacterial pneumonia, on days 1, 3, 7, 14, and 28 of ICU admission. Cumulative drug use, daily drug use, and weight-adjusted medication doses were examined.

RESULTS

The study population consisted of 37 patients with pH1N1 infection, 22 patients with non-pH1N1 viral pneumonia, and 46 patients with ARDS secondary to bacterial pneumonia. To achieve similar levels of sedation using the Richmond Agitation Sedation Scale, patients with pH1N1 were administered the highest cumulative median doses of fentanyl (11,230 μg; interquartile range [IQR] 3240-21,000), compared to 2400 μg (IQR 130-7130) in viral pneumonia and 2880 μg (IQR 600-6950) in ARDS (p < 0.001). Patients with pH1N1 were also administered the highest cumulative median doses of midazolam at 820 mg (IQR 330-1160), compared to 160 mg (IQR 20-390) in viral pneumonia and 160 mg (IQR 20-480 mg) in ARDS (p < 0.001). The pH1N1 group received the highest median daily fentanyl and midazolam doses on all study days. The pH1N1 group did not differ significantly in cumulative propofol dose compared with the other 2 study groups.

CONCLUSIONS

Sedative and analgesic use may be uniquely higher in critically ill patients with pH1N1 infection compared to patients with other infectious pneumonias. This finding may be important for resource planning in future pandemics. Further study is required to explore the underlying mechanisms for potentially higher sedative and analgesic requirements in this patient population.

Alprazolam prescribing in Tasmania: a two-fold intervention designed to reduce inappropriate prescribing and concomitant opiate prescription

OBJECTIVE

The population rate of alprazolam prescribing in Tasmania has been more than double that of national rates. Serious adverse events have been observed through co-administration of opioid medications with alprazolam. A two-fold intervention, comprising GP education coupled with changes to prescribing regulations, was designed with the intention to decrease inappropriate prescribing of alprazolam and thereby reduce adverse outcomes. The aim of this study was to assess the impact of the intervention on prescribing rates.

METHOD

We measured the number of alprazolam prescriptions for the years prior to and the year following the intervention. Health Insurance Commission data were utilized to enable comparison of subsidized prescription rates for alprazolam in Tasmania, and compared with national data. Participants were registered medical practitioners in Tasmania who were potential prescribers of alprazolam. The interventions were three GP Education Meetings during June 2007, one in each of the major regions of Tasmania, regarding evidence-based interventions for panic disorder. Changes to regulatory procedures to minimize co-prescription of alprazolam with opioids was implemented in September 2007.

RESULTS

A reduction in alprazolam prescribing in Tasmania occurred after the interventions.

CONCLUSION

Education can be an effective strategy to influence prescribing behaviour of doctors. It is likely that this effect can be augmented by adoption of more stringent regulatory requirements.

A rapid fluorimetric screening method for the 1,4-benzodiazepines: Determination of their metabolite oxazepam in urine

Oxazepam is the major metabolite screened in urine samples for the evidence of the use of benzodiazepine drugs. The methods currently used, however, are laborious and time consuming. This paper proposes an oxazepam detection method based on its hydrolysis and cyclization--a reaction catalysed by cerium (IV) in an ortho-phosphoric acid-containing medium--to form 2-chloro-9(10H)-acridinone, a strongly fluorescent molecule. The variables involved in the hydrolysis and cyclization stages were optimised. Oxazepam was detectable in the 5-900 ng mL(-1) range, with a detection limit of 4.15 ng mL(-1) for k=3. The method was successfully used for the determination of oxazepam in urine samples collected at different times after the oral administration of Valium and Tranxilium.

Effect of sleep apnea on cognition and mood

Obstructive sleep apnea syndrome (OSAS) is a common disorder in adults and children, which is characterized by repetitive transient reversible upper airway obstructions during sleep. Due to disrupted sleep architecture and intermittent hypoxemia, OSAS leads to impaired daytime functioning in various neuropsychological and affective domains. The most common abnormalities are executive dysfunction, impaired vigilance, depression, and possibly anxiety and, in children, hyperactivity. Optimal treatment of OSAS with continuous positive airway pressure may reverse the cognitive and affective dysfunction, however, in some patients a residual impairment persists. This persistent deficit, despite effective treatment, raises the possibility of a remaining subtle structural brain damage; such damage has been demonstrated through the use of sensitive functional and other neuroimaging techniques. Prefrontal cortical damage may underlie the cognitive dysfunction in OSAS. Early recognition and treatment may prevent this untoward effect of OSAS.

The condition of insomnia: etiopathogenetic considerations and their impact on treatment practices

Insomnia is conceived as the subjective complaint of reduced sleep quantity and/or quality, even in the absence of objective verification of sleep loss; it is the outcome of the interplay of many environmental, biological, and psychological factors, which can be distinguished into predisposing, precipitating and perpetuating. Predisposing and precipitating factors include various demographic characteristics and the occurrence of psychiatric or somatic illnesses as well as other stressful life events. The perpetuating factors, responsible for the development of chronicity of the complaint of insomnia, mainly involve a 24-hour state of hyperarousal and a vicious cycle of sleeplessness causing fear of sleeplessness which in turn leads to further hyperarousal and more sleeplessness. Particular psychological characteristics, including excessive use of denial and repression as well as a strong propensity for internalisation of emotions, are also among the main factors contributing to the psychophysiological activation and state of hyper-arousability commonly encountered among insomniac patients. The treatment should not only focus on ameliorating sleeplessness, it should also address all those factors that cause and maintain insomnia. An integrative management of insomnia includes education on sleep hygiene measures, behavioural, cognitive and psychodynamic psychotherapies, and the utilization of sleep-promoting drugs. Among the latter, only for the use of benzodiazepine or benzodiazepine-like hypnotics exists sufficient evidence for efficacy as well as adequate information on their side-effect profiles. Thus, these compounds are considered as the drugs of choice for the treatment of insomnia. It is recommended that the use of hypnotic drugs is restricted to the initial period of treatment; they should be rationally utilized within the context of a broad therapeutic program, which is based on a sound doctor-patient relationship and includes sleep hygiene education and the application of certain psychotherapeutic techniques in an individualized manner.

Postural Instability and Consequent Falls and Hip Fractures Associated with Use of Hypnotics in the Elderly

The aim of this review is to establish the relationship between treatment with hypnotics and the risk of postural instability and as a consequence, falls and hip fractures, in the elderly. A review of the literature was performed through a search of the MEDLINE, Ingenta and PASCAL databases from 1975 to 2005. We considered as hypnotics only those drugs approved for treating insomnia, i.e. some benzodiazepines and the more recently launched 'Z'-compounds, i.e. zopiclone, zolpidem and zaleplon. Large-scale surveys consistently report increases in the frequency of falls and hip fractures when hypnotics are used in the elderly (2-fold risk). Benzodiazepines are the major class of hypnotics involved in this context; falls and fractures in patients taking Z-compounds are less frequently reported, and in this respect, zolpidem is considered as at risk in only one study. It is important to note, however, that drug adverse effect relationships are difficult to establish with this type of epidemiological data-mining. On the other hand, data obtained in laboratory settings, where confounding factors can be eliminated, prove that benzodiazepines are the most deleterious hypnotics at least in terms of their effects on body sway. Z-compounds are considered safer, probably because of their pharmacokinetic properties as well as their selective pharmacological activities at benzodiazepine-1 (BZ(1)) receptors. The effects of hypnotics on balance, gait and equilibrium are the consequence of differential negative impacts on vigilance and cognitive functions, and are highly dose- and time-dependent. Z-compounds have short half-lives and have less cognitive and residual effects than older medications. Some practical rules need to be followed when prescribing hypnotics in order to prevent falls and hip fractures as much as possible in elderly insomniacs, whether institutionalised or not. These are: (i) establish a clear diagnosis of the sleep disorder; (ii) take into account chronic conditions leading to balance and gait difficulties (motor and cognitive status); (iii) search for concomitant prescription of psychotropics and sedatives; (iv) use half the recommended adult dosage; and (v) declare any adverse effect to pharmacovigilance centres. Comparative pharmacovigilance studies focused on the impact of hypnotics on postural stability are very much needed.

Pharmacology and pharmacokinetics of sedatives and analgesics

The agents used for sedation and analgesia during endoscopy have complex pharmacokinetic and pharmacodynamic properties. Knowledge of these characteristics is necessary for determining the proper agent and dose for specific patient needs. Short-acting agents, such as fentanyl, midazolam, and propofol, provide rapid sedation with a short duration of action that allows patients to return to normal functioning rapidly. When designing a dosing regimen with these agents, age and organ (liver, kidney) function of patients and concomitant medications that may interfere with metabolic and elimination pathways must be considered.

Consensus on Drug Treatment, Definition and Diagnosis for Insomnia

Thirty-four experts and a literature supervisor got together in order to reach a 'consensus' regarding the definition, diagnosis and pharmacological treatment of insomnia. Insomnia is a subjective perception of dissatisfaction with the amount and/or quality of sleep. It includes difficulty in initiating or maintaining sleep or early awakening with inability to fall asleep again. It is associated with complaints of non-restorative sleep and dysfunction of diurnal alertness, energy, cognitive function, behaviour or emotional state, with a decrease in quality of life. The diagnosis is based on clinical and sleep history, physical examination and additional tests, although polysomnography is not routinely indicated. Therapy should include treatment of the underlying causes, cognitive and behavioural measures and drug treatment. Hypnotic therapy can be prescribed from the onset of insomnia and non-benzodiazepine selective agonists of the GABA-A receptor complex are the drugs of first choice. It is recommended that hypnotic treatment be maintained in cases where withdrawal impairs the patient's quality of life and when all other therapeutic measures have failed. Experience suggests that intermittent treatment is better than continuous therapy. The available data do not confirm safety of hypnotics in pregnancy, lactation and childhood insomnia. Benzodiazepines are not indicated in decompensated chronic pulmonary disease but no significant adverse effects on respiratory function have been reported with zolpidem and zopiclone in stable mild to moderate chronic obstructive pulmonary disease and in treated obstructive sleep apnoea syndrome. Data for zaleplon are inconclusive. If the patient recovers subjective control over the sleep process, gradual discontinuation of hypnotic treatment can be considered.