Benzodiazepine poisoning. Clinical and pharmacological considerations and treatment

Probe Electrospray Ionization Tandem Mass Spectrometry for the Detection and Quantification of Benzodiazepines

BACKGROUND

Legally prescribed benzodiazepines (BZDs) and designer BZDs are widely misused and must be determined in multiple contexts (eg, overdose, drug-facilitated sexual assaults, or driving under the influence of drugs). This study aimed to develop a method for measuring serum BZD levels using probe electrospray ionization (PESI) mass spectrometry and an isotope dilution approach.

METHODS

A tandem mass spectrometer equipped with a probe electrospray ionization source in multiple reaction monitoring mode was used. Isotope dilution was applied for quantification using a deuterated internal standard at a fixed concentration for alprazolam, bromazepam, diazepam, nordiazepam, oxazepam, temazepam, zolpidem, and zopiclone. This method included designer BZDs: clonazolam, deschloroetizolam, diclazepam, etizolam, flualprazolam, flubromazepam, flubromazolam, meclonazepam, nifoxipam, and pyrazolam. Sample preparation was done by mixing 10 µL of serum with 500 µL of an ethanol/ammonium formate 0.01 mol/L buffer. Complete validation was performed, and the method was compared with liquid chromatography coupled with mass spectrometry (LC-MS/MS) and immunoassays (IC) by analyzing 40 real samples.

RESULTS

The analysis time for identification and quantification of the 18 molecules was 2.5 minutes. This method was fully validated, and the limits of quantification varied from 5 to 50 mcg/L depending on the molecule. In the 40 real samples, 100% of molecules (n = 89) were detected by both LC-MS/MS and PESI-MS/MS, and regression analysis showed excellent agreement between the 2 methods (r2 = 0.98). On IC, bromazepam and zolpidem were not detected in 2 and 1 cases, respectively.

CONCLUSIONS

PESI-MS/MS allows serum BZD detection and measurement. Given the isotope dilution approach, a calibration curve was not required, and its performance was similar to that of LC-MS/MS, and its specificity was higher than that of IC.

New Perspective for Drug-Drug Interaction in Perioperative Period

In this review, we aim to discuss current information on drug interactions in the perioperative period. During this period, patients receive several drugs that may interact with each other and affect the efficacy and safety of the treatment. There are three types of drug interactions: pharmacodynamic, pharmacokinetic, and pharmaceutical. It is important to recognize that drug interactions may increase the toxicity of the drug or reduce its efficacy, increasing the risk of complications in the perioperative period. This review describes the most commonly used perioperative drugs approved by the FDA and some of the described interactions between them. Thoroughly reviewing a patient's medication list and identifying potential interactions are essential steps in minimizing risks. Additionally, vigilant monitoring of patients during and after surgery plays a pivotal role in early detection of any signs of drug interactions. This article emphasizes the significance of addressing DDIs in the perioperative period to ensure patient well-being and advocates for the implementation of careful monitoring protocols to promptly identify and manage potential interactions.

Predicting benzodiazepine prescriptions: A proof-of-concept machine learning approach

Introduction

Benzodiazepines are the most commonly prescribed psychotropic medications, but they may place users at risk of serious adverse effects. Developing a method to predict benzodiazepine prescriptions could assist in prevention efforts.

Methods

The present study applies machine learning methods to de-identified electronic health record data, in order to develop algorithms for predicting benzodiazepine prescription receipt (yes/no) and number of benzodiazepine prescriptions (0, 1, 2+) at a given encounter. Support-vector machine (SVM) and random forest (RF) approaches were applied to outpatient psychiatry, family medicine, and geriatric medicine data from a large academic medical center. The training sample comprised encounters taking place between January 2020 and December 2021 (N = 204,723 encounters); the testing sample comprised data from encounters taking place between January and March 2022 (N = 28,631 encounters). The following empirically-supported features were evaluated: anxiety and sleep disorders (primary anxiety diagnosis, any anxiety diagnosis, primary sleep diagnosis, any sleep diagnosis), demographic characteristics (age, gender, race), medications (opioid prescription, number of opioid prescriptions, antidepressant prescription, antipsychotic prescription), other clinical variables (mood disorder, psychotic disorder, neurocognitive disorder, prescriber specialty), and insurance status (any insurance, type of insurance). We took a step-wise approach to developing a prediction model, wherein Model 1 included only anxiety and sleep diagnoses, and each subsequent model included an additional group of features.

Results

For predicting benzodiazepine prescription receipt (yes/no), all models showed good to excellent overall accuracy and area under the receiver operating characteristic curve (AUC) for both SVM (Accuracy = 0.868-0.883; AUC = 0.864-0.924) and RF (Accuracy = 0.860-0.887; AUC = 0.877-0.953). Overall accuracy was also high for predicting number of benzodiazepine prescriptions (0, 1, 2+) for both SVM (Accuracy = 0.861-0.877) and RF (Accuracy = 0.846-0.878).

Discussion

Results suggest SVM and RF algorithms can accurately classify individuals who receive a benzodiazepine prescription and can separate patients by the number of benzodiazepine prescriptions received at a given encounter. If replicated, these predictive models could inform system-level interventions to reduce the public health burden of benzodiazepines.

The clinical effect of intravenous lipid emulsion on rabbits medicated with diazepam

Intravenous lipid emulsions (ILE) have been increasingly used to reverse a wide range of lipophilic drug intoxications. However, it is still unknown if these emulsions interfere with other lipophilic drugs routinely used while treating intoxicated patients, such as diazepam, one of the main antiepileptic drugs. Therefore, the objective of the present study was to evaluate whether the administration of a 20% ILE interferes with diazepam's clinical effect. We randomly allocated thirty rabbits to five groups. Three of those groups received diazepam (1.0 mg/kg, IV), one of which did not receive any additional treatment, while the two remaining groups were treated with ILE or lactated ringer solution (1.5 mL/kg followed by 0.25 mL/kg/min for 30 min). The fourth group only received lipid emulsion, and the fifth only lactated ringer. Successive neurological exams at 20 min intervals for a total of 100 min were performed to assess the rabbits' neurological state. We concluded that the ILE did not interfere with diazepam's clinical effect but, although unlikely, the possibility of recurrence of a sedative effect should be considered.

Strategies for the treatment of acute benzodiazepine toxicity in a clinical setting: the role of antidotes

INTRODUCTION

Although not a potentially life-threatening poisoning, benzodiazepine (BZD) intoxication may be life-threatening in special situations/populations or those with background diseases.

AREAS COVERED

The aim of this review is to evaluate all possible treatment options available in the literature for the management of benzodiazepine poisoning with special attention to antidote administration. We conducted a literature search using PubMed, Google Scholar, EMBASE, and Cochrane central register from 1 January 1980 to 10 November 2021 using keywords 'benzodiazepine,' 'poisoning,' 'toxicity,' 'intoxication,' and 'treatment.'

EXPERT OPINION

Careful patient selection, ideally by a clinical toxicologist, may decrease the complications of flumazenil and add to its efficacy. The cost-to-benefit ratio should be considered in every single patient who is a candidate for flumazenil administration. In case a decision has been made to administer flumazenil, careful consideration of the possible contraindications is essential. We recommend slow administration of low doses of flumazenil (0.1 mg/minute) to avoid complications or withhold the administration with development of first signs of adverse effects. The main treatment of benzodiazepine toxicity is conservative with administration of activated charcoal, monitoring of the vital signs, prevention of aspiration and development of deep vein thrombosis due to prolonged immobilization, and respiratory support.

Reactive metabolites of the anticonvulsant drugs and approaches to minimize the adverse drug reaction

Several generations of antiepileptic drugs (AEDs) are available in the market for the treatment of seizures, but these are amalgamated with acute to chronic side effects. The most common side effects of AEDs are dose-related, but some are idiosyncratic adverse drug reactions (ADRs) that transpire due to the formation of reactive metabolite (RM) after the bioactivation process. Because of the adverse reactions patients usually discontinue the medication in between the treatment. The AEDs such as valproic acid, lamotrigine, phenytoin etc., can be categorized under such types because they form the RM which may prevail with life-threatening adverse effects or immune-mediated reactions. Hepatotoxicity, teratogenicity, cutaneous hypersensitivity, dizziness, addiction, serum sickness reaction, renal calculi, metabolic acidosis are associated with the metabolites of drugs such as arene oxide, N-desmethyldiazepam, 2-(1-hydroxyethyl)-2-methylsuccinimide, 2-(sulphamoy1acetyl)-phenol, E-2-en-VPA and 4-en-VPA and carbamazepine-10,11-epoxide, etc. The major toxicities are associated with the moieties that are either capable of forming RM or the functional groups may itself be too reactive prior to the metabolism. These functional groups or fragment structures are typically known as structural alerts or toxicophores. Therefore, minimizing the bioactivation potential of lead structures in the early phases of drug discovery by a modification to low-risk drug molecules is a priority for the pharmaceutical companies. Additionally, excellent potency and pharmacokinetic (PK) behaviour help in ensuring that appropriate (low dose) candidate drugs progress into the development phase. The current review discusses about RMs in the anticonvulsant drugs along with their mechanism vis-a-vis research efforts that have been taken to minimize the toxic effects of AEDs therapy.

Repurposing of escitalopram oxalate and clonazepam in combination with ciprofloxacin and sulfamethoxazole-trimethoprim for treatment of multidrug-resistant microorganisms and evaluation of the cleavage capacity of plasmid DNA

Bacterial resistance has become one of the most serious public health problems, globally, and drug repurposing is being investigated to speed up the identification of effective drugs. The aim of this study was to investigate the repurposing of escitalopram oxalate and clonazepam drugs individually, and in combination with the antibiotics ciprofloxacin and sulfamethoxazole-trimethoprim, to treat multidrug-resistant (MDR) microorganisms and to evaluate the potential chemical nuclease activity. The minimum inhibitory concentration, minimum bactericidal concentration, fractional inhibitory concentration index, and tolerance level were determined for each microorganism tested. In vitro antibacterial activity was evaluated against 47 multidrug-resistant clinical isolates and 11 standard bacterial strains from the American Type Culture Collection. Escitalopram oxalate was mainly active against Gram-positive bacteria, and clonazepam was active against both Gram-positive and Gram-negative bacteria. When associated with the two antibiotics mentioned, they had a significant synergistic effect. Clonazepam cleaved plasmid DNA, and the mechanisms involved were oxidative and hydrolytic. These results indicate the potential for repurposing these non-antibiotic drugs to treat bacterial infections. However, further studies on the mechanism of action of these drugs should be performed to ensure their safe use.

Polysubstance use in the U.S. opioid crisis

Interventions to address the U.S. opioid crisis primarily target opioid use, misuse, and addiction, but because the opioid crisis includes multiple substances, the opioid specificity of interventions may limit their ability to address the broader problem of polysubstance use. Overlap of opioids with other substances ranges from shifts among the substances used across the lifespan to simultaneous co-use of substances that span similar and disparate pharmacological categories. Evidence suggests that nonmedical opioid users quite commonly use other drugs, and this polysubstance use contributes to increasing morbidity and mortality. Reasons for adding other substances to opioids include enhancement of the high (additive or synergistic reward), compensation for undesired effects of one drug by taking another, compensation for negative internal states, or a common predisposition that is related to all substance consumption. But consumption of multiple substances may itself have unique effects. To achieve the maximum benefit, addressing the overlap of opioids with multiple other substances is needed across the spectrum of prevention and treatment interventions, overdose reversal, public health surveillance, and research. By addressing the multiple patterns of consumption and the reasons that people mix opioids with other substances, interventions and research may be enhanced.

A New Tool to Tackle the Opioid Epidemic: Description, Utility, and Results from the Maine Diversion Alert Program

STUDY OBJECTIVE

The opioid epidemic continues to impact the United States, and new strategies are needed to combat this epidemic. The objective of this study was to analyze 2015 drug arrest data from Maine's Diversion Alert (DA) program (diversionalert.org), compare arrest data between the first quarters of 2015 and 2016, and provide an analysis of the sex differences in the arrests as well as information about DA use.

STUDY DESIGN

This was a population-based descriptive study using data from the Maine DA program. The study population consisted of persons arrested for prescription, nonprescription, or illicit drugs.

DATA SOURCE

DA database.

MEASUREMENTS AND MAIN RESULTS

The DA program addresses Maine's prescription drug abuse epidemic with innovative resources that provide access to drug arrest data for health care providers to identify and respond to patients at risk for overdose, those engaged in illegal prescription drug distribution, and those who need treatment. Drug arrest data from 2015 (2723 arrests) and the first quarter of 2016 (788 arrests) were compared and analyzed. The drugs implicated in the arrests were organized by Drug Enforcement Agency (DEA) schedule category and whether they were pharmaceuticals (synthesized and distributed by a pharmaceutical company) or nonpharmaceuticals (grown or synthesized in clandestine laboratories). Most arrests were for possession (64.5%) followed by trafficking (23.8%). Heroin was listed in more than three-quarters (76.4%) of the Schedule I arrests, followed by marijuana (11.7%) and "bath salts" (6.3%). Cocaine and crack cocaine were implicated in almost half (46.7%) of the Schedule II arrests, followed by oxycodone (21.0%) and methamphetamine/amphetamine (15.8%). Buprenorphine was responsible for almost all (96.7%) of the Schedule III arrests. The benzodiazepines alprazolam (34.3%), clonazepam (33.8%), diazepam (11.9%), and lorazepam (8.5%) were listed in the preponderance of the Schedule IV arrests. Arrests increased in 2016 by 49.2% for heroin (p<0.01) and 170.0% for methamphetamine (p≤0.0005) relative to 2015. Arrests for trafficking increased by 42.9% (p<0.05). Males outnumbered females 2:1 in DA. Schedule IV agents accounted for only 6.8% of arrests for males versus 11.5% for females (p≤0.0001). Conversely, Schedule I agents were implicated in 33.0% of arrests for males versus only 27.3% for females (p<0.005).

CONCLUSION

DA is an important tool for providing timely information for health care providers regarding individuals with a history of past misuse of psychotherapeutic agents, particularly opioids and stimulants.

Sedation and Analgesia

Patients in the cardiothoracic intensive care unit (CTICU) are subject to numerous physical and mental stresses. While most of these cannot be completely eliminated, intensivists have many tools in their armamentarium to alleviate patients' pain and suffering. This chapter will consider the importance of analgesia and sedation in the CTICU and the relevant consequences of over- or under-treatment. We will examine the tools available for monitoring and titrating analgesia and sedation in critically ill patients. The major classes of medications available will be reviewed, with particular attention to their clinical effects, metabolism and excretion, and hemodynamic characteristics. Lastly, experimental evidence will be assessed regarding the best strategies for treatment of pain and agitation in the CTICU, including use of non-pharmacologic adjuvants.

Outpatient treatment of acute poisoning by substances of abuse: a prospective observational cohort study

Background

Procedures for the clinical assessment of acute poisoning by substances of abuse should identify patients in need of hospital admission and avoid hazardous discharges, while keeping the observation time short. We assess the safety of a systematic procedure developed at the Oslo Accident and Emergency Outpatient Clinic (OAEOC).

Methods

All patients 12 years and older treated for acute poisoning by substances of abuse at the OAEOC were included consecutively from October 2011 to September 2012. Data were collected on pre-set registration forms. Information on re-presentations to health services nation-wide during the first week following discharge was retrieved from the Norwegian Patient Register and from local electronic medical records. Information on fatalities was obtained from the Norwegian Cause of Death Registry.

Results

There were 2343 cases of acute poisoning by substances of abuse. The main toxic agent was ethanol in 1291 (55 %) cases, opioids in 539 (23 %), benzodiazepines in 194 (8 %), central stimulants in 132 (6 %), and gamma-hydroxybutyrate (GHB) in 105 (4 %). Median observation time was four hours. The patient was hospitalised in 391 (17 %) cases. Two patients died during the first week following discharge, both from a new opioid poisoning. Among 1952 discharges, 375 (19 %) patients re-presented at the OAEOC or a hospital within a week; 13 (0.7 %) with a diagnosis missed at the index episode, 169 (9 %) with a new poisoning, 31 (2 %) for follow-up of concomitant conditions diagnosed at index, and 162 (8 %) for unrelated events. Among the patients with missed diagnoses, five needed further treatment for the same poisoning episode, two were admitted with psychosis, one had hemorrhagic gastritis, another had fractures in need of surgery and four had minor injuries.

Conclusion

The procedure in use at the OAEOC can be considered safe and could be implemented elsewhere. The high re-presentation rate calls for better follow-up.

A Longitudinal Study of Multiple Drug Use and Overdose Among Young People Who Inject Drugs

OBJECTIVES

To determine the association between multiple drug use and nonfatal overdose among young people (younger than 30 years) who inject drugs.

METHODS

We completed a longitudinal study of 173 injection drug users younger than 30 years living in San Francisco, California, between April 2012 and February 2014.

RESULTS

The odds of nonfatal overdose increased significantly as heroin and benzodiazepine pill-taking days increased and when alcohol consumption exceeded 10 drinks per day compared with 0 drinks per day.

CONCLUSIONS

Heroin, benzodiazepine, and alcohol use were independently associated with nonfatal overdose over time among young people who inject drugs. Efforts to address multiple central nervous system depressant use remain an important component of a comprehensive approach to overdose, particularly among young people.

Drug overdose surveillance using hospital discharge data

OBJECTIVES

We compared three methods for identifying drug overdose cases in inpatient hospital discharge data on their ability to classify drug overdoses by intent and drug type(s) involved.

METHODS

We compared three International Classification of Diseases, Ninth Revision, Clinical Modification code-based case definitions using Kentucky hospital discharge data for 2000-2011. The first definition (Definition 1) was based on the external-cause-of-injury (E-code) matrix. The other two definitions were based on the Injury Surveillance Workgroup on Poisoning (ISW7) consensus recommendations for national and state poisoning surveillance using the principal diagnosis or first E-code (Definition 2) or any diagnosis/E-code (Definition 3).

RESULTS

Definition 3 identified almost 50% more drug overdose cases than did Definition 1. The increase was largely due to cases with a first-listed E-code describing a drug overdose but a principal diagnosis that was different from drug overdose (e.g., mental disorders, or respiratory or circulatory system failure). Regardless of the definition, more than 53% of the hospitalizations were self-inflicted drug overdoses; benzodiazepines were involved in about 30% of the hospitalizations. The 2011 age-adjusted drug overdose hospitalization rate in Kentucky was 146/100,000 population using Definition 3 and 107/100,000 population using Definition 1.

CONCLUSION

The ISW7 drug overdose definition using any drug poisoning diagnosis/E-code (Definition 3) is potentially the highest sensitivity definition for counting drug overdose hospitalizations, including by intent and drug type(s) involved. As the states enact policies and plan for adequate treatment resources, standardized drug overdose definitions are critical for accurate reporting, trend analysis, policy evaluation, and state-to-state comparison.

Benzodiazepines

The misuse and abuse of prescription medications in the United States continues to increase despite interventions by health care professionals, regulatory, and law enforcement agencies. Opioid analgesics are the leading class of prescription drugs that have caused unintentional overdose deaths. Benzodiazepines when taken alone are relatively safe agents in overdose. However, a 5-fold increase in deaths attributed to benzodiazepines occurred from 1999 to 2009. Emergency department visits related to opioid analgesics increased by 111% followed by benzodiazepines 89%. During 2003 to 2009, the 2 prescriptions drugs with the highest increase in death rates were oxycodone 264.6% and alprazolam 233.8%. Therefore, benzodiazepines have a significant impact on prescription drug unintentional overdoses second only to the opioid analgesics. The combination prescribing of benzodiazepines and opioid analgesics commonly takes place. The pharmacokinetic drug interactions between benzodiazepines and opioid analgesics are complex. The pharmacodynamic actions of these agents differ as their combined effects produce significant respiratory depression. Physician and pharmacy shopping by patients occurs, and prescription drug-monitoring programs can provide important information on benzodiazepine and opioid analgesic prescribing patterns and patient usage. Health care professionals need to inform patients and work closely with regulatory agencies and legislatures to stem the increasing fatalities from prescription drug unintentional overdoses.

Benzodiazepine-associated atrioventricular block

Dysrhythmias, although common in overdose situations, are not often seen after benzodiazepine exposures. We report two cases of transient atrioventricular block after benzodiazepine misuse. Case 1 is a 4-year-old boy who was found unresponsive after an ingestion of clonazepam. An electrocardiogram (EKG) performed on emergency department presentation demonstrated first-degree atrioventricular block (PR 206 ms). After flumazenil administration, he developed second-degree atrioventricular block (Mobitz Type 1). EKG abnormalities resolved by morning. Serum clonazepam was 478 ng/mL (laboratory clonazepam reference range, 10-75 ng/mL with a dose of up to 6 mg/day) 5 hours after being found unresponsive. Case 2 is a 23-year-old man who presented to the emergency department after ingesting risperidone, combination hydrocodone/acetaminophen, and alprazolam. On arrival, his EKG demonstrated sinus bradycardia with a PR interval of 182 msec. He subsequently developed second-degree atrioventricular block (Mobitz Type I). Sinus bradycardia with resolution of his atrioventricular block (PR 200 ms) was seen on a third EKG performed 5 hours after presentation. These two patients demonstrated transient first- and second-degree atrioventricular block after benzodiazepine exposure. Benzodiazepines have been shown to alter L-type Ca2+ channel function. This alteration in function may account for the dysrhythmias seen in our patients. Together, these cases serve to remind clinicians of this rare but potentially serious complication associated with benzodiazepine exposure.

A sound sleep

Benzodiazepine is a commonly encountered agent of poisoning, which is readily diagnosed by a pertinent history of drug ingestion and the clinical scenario. In the absence of a proper drug history, the diagnosis becomes challenging. Proper clinical assessment, urine assays and imaging play a very important role in reaching the diagnosis. We present a case of acute benzodiazepine poisoning without a history of drug intake. The key pointers toward diagnosis were an unarousable state with obstructive apnea. Magnetic resonance imaging (MRI) of the brain revealed peculiar symmetrical isolated globus pallidus T2 hyperintensity. We believe this to be the first report of isolated bilateral basal ganglia T2-weighted hyperintensity in MRI in the setting of acute benzodiazepine poisoning from India.

Toxicokinetics of a dipyridamole (Persantin) intoxication: Case report

We report a case of a 51-year-old woman who was admitted to the hospital after ingestion of large doses of dipyridamole (12 g), temazepam (1 g) and oxazepam (0.2 g) with suicidal intent. The highest dipyridamole concentration that was measured in serum was 9.2 mg/L, which was paralleled by impaired platelet activation. For temazepam and oxazepam, peak serum concentrations were 8.5 and 1.3 mg/L, respectively. The patient was treated with activated charcoal, magnesium sulfate and aminophylline and could be discharged in good physical condition within 17 hours. This is the first report that provides toxicokinetic data and a corresponding pharmacodynamic effect after an intoxication with dipyridamole.

Benzodiazepine prescription and length of hospital stay at a Japanese university hospital

Background

The relationship between bed days and benzodiazepine prescription (BDZ) in Western countries is inconclusive, and no hospital-based report has documented this phenomenon in Japan. This study was done to assess the association between bed days and BDZ in a Japanese hospital.

Methods

21,489 adult patients (55.1% men, mean age 59.9 years old) hospitalized between April, 2005 and December, 2006 were enrolled in the study. Patient age, sex, ICD-10 diagnosis, prescription profile, and days of hospital stay were assessed in 13 non-psychiatric departments using a computer ordering system. Patients prescribed a benzodiazepine during hospitalization were defined as positive.

Results

Of the total sample, 19.9% were allocated to the benzodiazepine (+) group. Female sex and older age were significant factors associated with benzodiazepine prescription. The median number of bed days was 13, and the likelihood of BDZ significantly increased with the number of bed days, even after controlling for the effects of age, gender, and ICD-10 diagnosis. For example, when the analysis was limited to patients with 50 bed days or longer, the percentage of BDZ (32.7%) was equivalent to that of a report from France.

Conclusion

Irrespective of department or disease, patients prescribed benzodiazepine during their hospital stay tended to have a higher number of bed days in the hospital. The difference in the prevalence of BDZ between this study and previous Western studies might be attributed to the relatively short length of hospital stay in this study. Because BDZs are often reported to be prescribed to hospitalized patients without appropriate documentation for the indications for use, it is important to monitor the rational for prescriptions of benzodiazepine carefully, for both clinical and economical reasons.

G-protein-coupled receptors: from classical modes of modulation to allosteric mechanisms

Heterotrimeric G-protein-coupled receptors (GPCRs) represent a large protein family responsible for mediating extracellular to intracellular signaling within a broad range of physiological contexts. Various conventional models have been used to describe their interactions with ligands and G-proteins. In recent years, however, numerous novel ligand-receptor interactions not adequately addressed by classical receptor theory have been recognized. In addition to traditional orthosteric ligands, many GPCRs can bind allosteric ligands that modulate receptor activity by interacting with distinct or overlapping receptor sites. Such ligands include positive allosteric modulators, which have become the focus of pharmaceutical drug discovery programs and have gained the attention of a growing body of basic and translational researchers within the academic community. Here, we review the fundamental aspects of allosteric GPCR modulation by small-molecule ligands, with particular focus on the emerging position of positive allosteric modulators in modern drug discovery.

Cerebral and plasma kinetics of a high dose of midazolam and correlations with its respiratory effects in rats

Benzodiazepine poisoning causes coma and respiratory depression. Our objective was to determine whether, and to what extent, arterial blood gas disturbances correlated with blood or cerebral kinetics of midazolam. A 160 mgkg(-1) single dose of midazolam was infused intravenously over 20 min in catheterized male Sprague-Dawley rats. Midazolam kinetics was simultaneously determined in plasma and brain using striatal microdialysis. Midazolam concentrations were measured using a high-performance liquid chromatographic assay with ultraviolet detection. Midazolam (160 mgkg(-1)) reproducibly induced deep coma with respiratory acidosis. Plasma midazolam kinetics was well described by a bi-exponential model, with an elimination half-life of 6.4+/-1.8 h. The striatal dialysate concentration peaked at 50.0+/-8.9 min after the end of infusion, with a significant delay to peak concentration compared to plasma. Respiratory depression, assessed by the elevation in PaCO2, was more closely correlated with midazolam striatal dialysate rather than plasma kinetics. These results suggest a central mechanism for midazolam respiratory effects at toxic doses in rats. In conclusion, our study showed a delayed onset in peak PaCO2 and pH effects after the slow infusion of a toxic dose of midazolam in rats. The effects on arterial blood gases were better correlated with midazolam striatal concentrations than with plasma concentrations. This study may contribute to better understanding of benzodiazepine-induced respiratory depression in poisonings.

Pharmacological management of acute agitation

Acute agitation occurs in a variety of medical and psychiatric conditions, and when severe can result in behavioural dyscontrol. Rapid tranquillisation is the assertive use of medication to calm severely agitated patients quickly, decrease dangerous behaviour and allow treatment of the underlying condition. Intramuscular injections of typical antipsychotics and benzodiazepines, given alone or in combination, have been the treatment of choice over the past few decades. Haloperidol and lorazepam are the most widely used agents for acute agitation, are effective in a wide diagnostic arena and can be used in medically compromised patients. Haloperidol can cause significant extrapyramidal symptoms, and has rarely been associated with cardiac arrhythmia and sudden death. Lorazepam can cause ataxia, sedation and has additive effects with other CNS depressant drugs.Recently, two fast-acting preparations of atypical antipsychotics, intramuscular ziprasidone and intramuscular olanzapine, have been developed for treatment of acute agitation. Intramuscular ziprasidone has shown significant calming effects emerging 30 minutes after administration for acutely agitated patients with schizophrenia and other nonspecific psychotic conditions. Intramuscular ziprasidone is well tolerated and has gained widespread use in psychiatric emergency services since its introduction in 2002. In comparison with other atypical antipsychotics, ziprasidone has a relatively greater propensity to increase the corrected QT (QTc) interval and, therefore, should not be used in patients with known QTc interval-associated conditions. Intramuscular olanzapine has shown faster onset of action, greater efficacy and fewer adverse effects than haloperidol or lorazepam in the treatment of acute agitation associated with schizophrenia, schizoaffective disorder, bipolar mania and dementia. Intramuscular olanzapine has been shown to have distinct calming versus nonspecific sedative effects. The recent reports of adverse events (including eight fatalities) associated with intramuscular olanzapine underscores the need to follow strict prescribing guidelines and avoid simultaneous use with other CNS depressants. Both intramuscular ziprasidone and intramuscular olanzapine have shown ease of transition to same-agent oral therapy once the episode of acute agitation has diminished. No randomised, controlled studies have examined either agent in patients with severe agitation, drug-induced states or significant medical comorbidity. Current clinical experience and one naturalistic study with intramuscular ziprasidone suggest that it is efficacious and can be safely used in such populations. These intramuscular atypical antipsychotics may represent a historical advance in the treatment of acute agitation.

Chronic high-dose nitrazepam dependence 123I-IMP SPECT and EEG studies

A patient who took 50-100 mg nitrazepam per day for 25 years is presented. (123)I-IMP SPECT (autoradiography method) and EEG were performed sequentially on the subject during and after the withdrawal syndrome. Severe hypoperfusion of the whole brain on SPECT and diffuse slow activity on EEG were demonstrated during the withdrawal syndrome and subsequently remarkably improved. However, the hypofrontal pattern on both early and delayed images in SPECT was unchanged. The changes observed on SPECT and EEG reflect the pathophysiology of dependence and withdrawal. Additionally, the hypofrontal pattern remained unchanged suggesting that organic brain damage can develop as a result of chronic high-dose benzodiazepine abuse.

Drug Poisoning and Overdose for the Health Professional: Review of Select Over-the-Counter (OTC) and Prescription Medications

Exposure to over-the-counter and prescription medications can pose significant therapeutic and health hazards to patients, and present health care professionals with scenarios that require proper assessment and treatment. Knowing when an exposure to or overdose of a drug requires emergency medical attention is equally as important as to knowing when such assistance is not necessary—that simple treatment measures performed at home will suffice. This current discussion is intended to highlight select principles and clinical information pertaining to common drug exposures and overdoses, but not replace the full spectrum of information that would be available to health care professionals (and the lay public) by contacting their nearest poison control center. Many of the basic principles and concerns that are encountered with exposures to chemicals (i.e., route of exposure, patient medical history, quantity of the substance involved, elapsed time since the initial exposure, etc.) apply equally well to drug exposures. Likewise, evaluating each of these variables will determine which type of treatment approaches are, and are not, considered in situations of drug (or chemical) exposure and overdose.

Acute neurologic complications of drug and alcohol abuse

Recreationally abused substances include both legal and illegal agents, broadly classified as opioids, psychostimulants, sedatives, cannabis (marijuana), hallucinogens, inhalants, dissociative anesthetics (phencyclidine), anticholinergics, ethanol, and tobacco. These substances are associated with an array of neurological emergencies resulting from overdose, withdrawal, and other medical and neurological complications.

A guide to the safety of CNS-active agents during breastfeeding

For most agents with CNS activity, there are limited data regarding their safety in breastfeeding. Any decision to institute treatment for a neurological or psychiatric disorder must weigh the benefits of maternal treatment against the potential harm to the breastfeeding mother of withholding medication which may improve her illness. For the neonate, one must balance the risk of medication exposure against the benefit of receiving breast milk. Most tricyclic antidepressants can be used in lactating women. Because of the limited data, selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors should only be used with due consideration of the potential adverse effects. Breastfeeding is best avoided by women who require lithium therapy, because of both the immature excretory systems in the infant and relatively high doses received by the infant. There is little information about the safety of antipsychotic medications in breastfeeding. Concerns include toxicity and abnormal neurological development in the infant. These agents may be used with caution. Most agents which cause depression of the CNS, including opiates and sedatives, can be used in small doses and for short courses in breastfeeding mothers. Most anticonvulsants can be used in lactating women. Reference texts and consultation with experts are useful adjuncts to discussion of the risks and benefits of therapy with the patient. The scope of this review is limited to drugs with therapeutic uses, thus drugs of abuse are not discussed, nor are caffeine and alcohol (ethanol).

Relative toxicity of benzodiazepines in overdose

OBJECTIVE

To assess the sedative effects in overdose of temazepam and oxazepam compared with other benzodiazepines to determine if this explains reported differences in fatal toxicity.

DESIGN

Cohort study of patients admitted with benzodiazepine poisoning.

SETTING

Newcastle, Australia.

SUBJECTS

303 patients who had ingested benzodiazepine alone or in combination with alcohol and presented to a general hospital which served a well defined geographical area.

MAIN OUTCOME MEASURES

Degree of sedation: Glasgow coma score, McCarron Score, and whether patients were stuporose or comatose.

RESULTS

Oxazepam produced less and temazepam more sedation than other benzodiazepines. Unadjusted odds ratios for coma with oxazepam and temazepam compared with other benzodiazepines were 0.0 (95% confidence interval 0.0 to 0.85) and 1.86 (0.68 to 4.77) respectively, chi 2 = 7.08, 2df, P = 0.03. After adjustment for potentially confounding effects of age, dose ingested, and coingestion of alcohol, the odds ratios were 0.22 (0.0 to 1.43) for oxazepam and 1.94 (0.57 to 6.23) for temazepam. Similar results were obtained for other measures of sedation.

CONCLUSIONS

These results were in accordance with fatal toxicity indices derived from coroners' data on mortality and rates of prescription. The relative safety of benzodiazepines in overdose should be a consideration when they are prescribed.

Benzodiazepines for acute pain in children

When pediatric pain is refractory and unresponsive to appropriate use of analgesic agents, there might be additional physical or psychologic dimensions of the pain that are not addressed by the analgesics. In addition to appropriate analgesic therapy, the psychologic needs of the child should be directly addressed and appropriate adjunctive physical modalities employed. Although benzodiazepines lack direct analgesic effects, they can reduce the distress associated with acute pain states by decreasing anxiety, insomnia, and muscle spasms that can be associated with acute pain. Intermediate or long-acting benzodiazepines in modest doses can be useful adjunctive agents when used short term for the treatment of selected acute pain complaints. In the highly distressed school-age child or adolescent with pain complaints relatively unresponsive to appropriate care, judicious use of benzodiazepines is worthy of consideration.