Understanding the pharmacokinetics of anxiolytic drugs

Characterization of Extended-Release Lorazepam: Pharmacokinetic Results Across Phase 1 Clinical Studies

PURPOSE/BACKGROUND

Once-daily extended-release (ER) lorazepam was developed to reduce fluctuations in plasma levels compared with lorazepam immediate-release (IR) for short-term anxiety relief. Here we report a series of phase 1 randomized, open-label, multiperiod crossover studies characterizing ER lorazepam pharmacokinetics and safety in healthy adults.

METHODS/PROCEDURES

These phase 1 studies assessed the pharmacokinetics of ER lorazepam administered: (study 1) 3 mg once daily versus IR lorazepam 1 mg 3 times a day (TID; every 8 hours), (study 2) with or without food, and (study 3) intact versus sprinkled onto food. Study 3 further evaluated the proportionality of 1 × 4- versus 4 × 1-mg doses. Safety was also monitored.

FINDINGS/RESULTS

There were 43, 27, and 29 subjects who completed studies 1, 2, and 3, respectively. The 90% confidence intervals for Cmax,SS, Cmin, and AUCTAU,SS of once-daily ER lorazepam compared with IR given TID were within 80% to 125% limits establishing steady-state bioequivalence. Maximum mean lorazepam concentrations were achieved at 11 hours compared with 1 hour after dosing for ER versus IR lorazepam, respectively. Pharmacokinetic parameters (Cmax, AUClast or AUC0-t, AUCinf or AUC0-inf) of ER lorazepam were bioequivalent whether taken with or without food, administered intact or sprinkled onto food, or administered as intact 1 × 4- versus 4 × 1-mg capsules. No serious safety concerns were found.

IMPLICATIONS/CONCLUSIONS

Once-daily ER lorazepam provided a pharmacokinetic profile bioequivalent to IR lorazepam given TID and was well tolerated in healthy adults across all phase 1 studies. These data suggest that ER lorazepam could be an alternative for patients currently treated with IR lorazepam.

G protein-coupled receptors in neurodegenerative diseases and psychiatric disorders

Neuropsychiatric disorders are multifactorial disorders with diverse aetiological factors. Identifying treatment targets is challenging because the diseases are resulting from heterogeneous biological, genetic, and environmental factors. Nevertheless, the increasing understanding of G protein-coupled receptor (GPCR) opens a new possibility in drug discovery. Harnessing our knowledge of molecular mechanisms and structural information of GPCRs will be advantageous for developing effective drugs. This review provides an overview of the role of GPCRs in various neurodegenerative and psychiatric diseases. Besides, we highlight the emerging opportunities of novel GPCR targets and address recent progress in GPCR drug development.

Etizolam and Its Major Metabolites: A Short Review

Etizolam is a benzodiazepine (BZD). Etizolam is structurally different from BZDs as a thiophene replaces the benzene ring and a triazole ring is fused to the diazepine ring, but etizolam's pharmacological profile is similar. Etizolam has been used to treat anxiety and panic disorders, to reduce depressive and somatization symptoms and to induce muscle relaxation. Etizolam is used recreationally due to its reinforcing and sedative effects. Etizolam is available in tablet or powder form or administered on blotter paper that can be placed on the tongue for oral absorption. Etizolam metabolizes into two major metabolites: α-hydroxyetizolam and 8-hydroxyetizolam, and all three compounds can be detected in different biological specimens using various common analytical techniques such as immunoassay, chromatography and mass spectrometry. Etizolam is a controlled drug in many countries around the globe but is approved for medical use in some countries, such as Japan, South Korea and Italy. This work is a collation and review of available literature on etizolam to help improve the fundamental understanding of its toxicology, outline best analytical practice, and aid interpretation of toxicology results.

Treatment of concurrent etizolam and tianeptine withdrawal following accidental overdose

Background

The availability of nonapproved psychoactive substances with addiction potential from internet sources poses a significant threat to public health. Polysubstance abuse or inadvertent contamination of preparations may result in clinically challenging intoxication and withdrawal syndromes.

Case Report

We report a case of a 32-year-old male with an approximate 2-year history of taking internet-obtained etizolam and tianeptine who presented to the hospital following an overdose. He experienced subsequent withdrawal symptoms consistent with benzodiazepine and opioid withdrawal. Initial attempts at managing symptoms with chlordiazepoxide 25 mg every 6 hours did not relieve his symptoms. On day 3 of admission, addiction medicine was consulted and his regimen was changed to diazepam 80 mg daily with additional as-needed diazepam based on etizolam equivalence. He also received a 5-day methadone taper with plans to transition to buprenorphine in the outpatient setting. Upon discharge he was referred to an addiction medicine specialist who was willing to continue a slow diazepam taper and initiate medications for opioid use disorder to manage both substance use disorders.

Discussion

This case report demonstrates the effectiveness of diazepam in managing benzodiazepine withdrawal from etizolam while concurrently using methadone to manage opioid withdrawal symptoms from tianeptine in a hospitalized patient following overdose. We highlight the importance of a warm handoff in considering the outpatient discharge plan.

Combretum lanceolatum extract reverses anxiety and seizure behavior in adult zebrafish through GABAergic neurotransmission: an in vivo and in silico study

Combretaceae are reported in the literature for presenting neuroprotective and anxiolytic effects in animal models. Combretum lanceolatum Pohl. has few scientific reports on its pharmacological effects. The aim of this study was to evaluate the anxiolytic and anticonvulsant effects of the ethanol extract from the leaves of C. lanceolatum Pohl. (EtFoCl) and its possible mechanism of GABAergic action in adult zebrafish. EtFoCl was subjected to determination of the total phenol concentration, identification of phytochemical flavonoids by HPLC and in vitro antioxidant activity test, open field test and 96-hour acute toxicity in zebrafish. Anxiolytic doses were tested for pentylenetetrazole-induced seizures in adult zebrafish. To study the mechanisms of action, molecular docking simulations were performed between the main phytochemicals and the GABAA receptor (anxiolytic activity) and carbonic anhydrase II (anticonvulsant). The non-toxic doses that caused motor impairment were assessed in acute and chronic anxiety using the light and dark test. EtFoCl had altered the animals' locomotion, presenting an effect similar to the anxiolytic and anticonvulsant. These effects were prevented with flumazenil (GABAA antagonist). The phytochemicals homoorientin and quercetin-3-O-galactoside coupling in a region close to that of the inhibitor diazepam (GABAA receptor). Regarding the anticonvulsant mechanism, Homoorientina and Isovitexina were identified as the most favorable for the complex form with the carbonic anhydrase enzyme. C. lanceolatum has pharmacological potential for the treatment of acute and chronic anxiety and seizures, which can be partially explained by an interaction with the GABAA receptor.Communicated by Ramaswamy H. Sarma.

A bibliometric analysis of the recent advances in diazepam from 2012 to 2021

Background: Diazepam is a classic benzodiazepine drug that has been widely used for disorders such as anxiety, sleep disorders, and epilepsy, over the past 59 years. The study of diazepam has always been an important research topic. However, there are few bibliometric analyses or systematic studies in this field. This study undertook bibliometric and visual analysis to ascertain the current status of diazepam research, and to identify research hotspots and trends in the past 10 years, to better understand future developments in basic and clinical research.

Methods: Articles and reviews of diazepam were retrieved from the Web of Science core collection. Using CiteSpace, VOSviewer, and Scimago Graphica software, countries, institutions, authors, journals, references, and keywords in the field were visually analyzed.

Results: A total of 3,870 publications were included. Diazepam-related literature had high volumes of publications and citations. The majority of publications were from the USA and China. The highest number of publications and co-citations, among the authors, was by James M Cook. Epilepsia and the Latin American Journal of Pharmacy were the journals with the most publications on diazepam and Epilepsia was the most frequently cited journal. Through a comprehensive analysis of keywords and references, we found that current research on diazepam has focused on its mechanism of action, application in disease, pharmacokinetics, risk, assessment, and management of use, status epilepticus, gamma-aminobutyric acid receptors (GABAR), intranasal formulation, gephyrin, and that ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) is the current research hotspot.

Conclusion: Research on diazepam is flourishing. We identified research hotspots and trends in diazepam research using bibliometric and visual analytic methods. The clinical applications, mechanisms of action, pharmacokinetics, and assessment and management of the use of diazepam are the focus of current research and the development trend of future research.

Voltage-clamp evidence of GABAA receptor subunit-specific effects: pharmacodynamic fingerprint of chlornordiazepam, the major active metabolite of mexazolam, as compared to alprazolam, bromazepam, and zolpidem

BACKGROUND

Anxiolytic benzodiazepines, due to their clinical effectiveness, are one of the most prescribed drugs worldwide, despite being associated with sedative effects and impaired psychomotor and cognitive performance. Not every GABA_A receptor functions in the same manner. Those containing α1 subunits are associated with sleep regulation and have a greater effect on the sedative-hypnotic benzodiazepines, whereas those containing α2 and/or α3 subunits are associated with anxiety phenomena and have a greater effect on the anxiolytic benzodiazepines. Therefore, characterization of the selectivity profile of anxiolytic drugs could translate into a significant clinical impact.

METHODS

The present study pharmacodynamically evaluated chlornordiazepam, the main active metabolite of mexazolam, upon GABA_A receptors containing α2 and/or α3, anxiety-related, and those containing an α1 subunit, associated with sleep modulation.

RESULTS

As shown by whole-cell patch-clamp data, chlornordiazepam potentiated GABA-evoked current amplitude in α2 and α3 containing receptors without changing the current amplitude in α1 containing receptors. However, current decay time increased, particularly in GABA_A receptors containing α1 subunits. In contrast, other anxiolytic benzodiazepines such as alprazolam, bromazepam, and zolpidem, all increased currents associated with GABA_A receptors containing the α1 subunit.

CONCLUSIONS

This novel evidence demonstrates that mexazolam (through its main metabolite chlornordiazepam) has a "pharmacodynamic fingerprint" that correlates better with an anxiolytic profile and fewer sedative effects, when compared to alprazolam, bromazepam and zolpidem, explaining clinical trial outcomes with these drugs. This also highlights the relevance of the pharmacological selectivity over GABA_A receptor subtypes in the selection of benzodiazepines, in addition to their clinical performance and pharmacokinetic characteristics.

The pharmacological treatment of acute vestibular syndrome

Acute vestibular syndrome (AVS) represents a clinical picture that involves urgent management due to the important procession of symptoms accompanying the event, which can be positively or negatively influenced by therapeutic choices and intervention timing. This forces a differential diagnosis and therapeutic choices to be made in conditions that are not always favorable and often not in the specialist field. In this work, we will examine in detail the pharmacological therapeutic possibilities, correlating them to the differential and, as far as possible, to the etiological diagnosis. In particular, the pharmacological possibilities for the two main conditions we can face will be investigated, namely, vestibular neuritis and posterior circulation stroke.

Pharmacogenetic profiling and individualised therapy in the treatment of degenerative spinal conditions

Patients presenting with degenerative spinal changes are often poor surgical candidates due to associated co-morbidities, frailty, or sarcopenia. Additionally, surgeries of a degenerative spine can prove difficult due to the distortion of normal surgical anatomy. Therefore, many patients are managed conservatively with a variety of modalities, including over-the-counter and prescription medications. Nevertheless, several patients do not experience adequate relief from pain with analgesic medications, precipitating multiple hospital visits, and usage of resources. As a result, back pain is regarded as a major economic burden, with total costs of associated treatment exceeding $100 billion annually. Pharmacogenetics is a relatively novel method of evaluating an individual's response to analgesic medications, through analysis of germline polymorphisms. It entails obtaining a genetic sample, often via buccal swab or peripheral blood sample, and genetic analysis achieved through either polymerase chain reaction +/- Sanger sequencing, microassays, restriction length fragment polymorphism analysis, or genetic library preparation and next generation sequencing. The potential efficacy of pharmacogenetic analysis has been highlighted across several specialities to date. However, a paucity of evidence exists regarding spine surgery populations. Nevertheless, regular prospective pharmacogenetic analysis may ultimately prove beneficial when concerning degenerative spinal cohorts due to aforementioned surgical and economic considerations. The purpose of this narrative review is to outline how metaboliser profile variants affect the pharmacokinetics of specific analgesia used to treat back pain, and to discuss the current potential and limitations of employing regular pharmacogenetic analysis for spine surgery populations with degenerative conditions.

A Retrospective Study of the Adjunctive Use of Gabapentin With Benzodiazepines for the Treatment of Benzodiazepine Withdrawal

Benzodiazepine withdrawal is a widespread problem with potentially severe and deadly consequences. Currently, the only medications available for treating benzodiazepine withdrawal are short-acting and long-acting benzodiazepines. Identifying other drugs to help in treating benzodiazepine withdrawal is necessary. Gabapentin, an anxiolytic drug that is also used off-label to treat alcohol withdrawal, is a potential candidate for modulating benzodiazepine withdrawal. Using electronic records from a large inpatient psychiatric facility, a retrospective study of 172 patients presenting with benzodiazepine withdrawal was conducted to determine if the coincidental use of gabapentin for other medical conditions was associated with better outcomes of benzodiazepine withdrawal (N=57 gabapentin, N=115 no gabapentin). The primary outcomes were hospital length of stay and total amount of benzodiazepines given (lorazepam milligram equivalent). In this retrospective analysis of electronic medical record data, the patients experiencing benzodiazepine withdrawal who received gabapentin as an adjunct to the use of benzodiazepines were administered a smaller amount of benzodiazepines and had a shorter length of hospital stay relative to the comparison group who did not receive adjunctive gabapentin. These results suggest the potential use of gabapentin as an adjunct to the use of benzodiazepines for treating benzodiazepine withdrawal. The limitations of this study included a small sample size and variability in medication management strategies across the sample.

Excitement-Induced Cutaneous Bleeding (Haematidrosis-like) in a Dog

A 15-month-old intact female Pitbull was referred because of recurrent, episodic, self-limiting, excitement-induced bleeding from nontraumatised skin. No abnormalities were detected upon physical examination. Subsequently, the dog went for a walk under the direct supervision of one of the authors, became overexcited and, after approximately five minutes, bloody liquid, with a patchy distribution, appeared along the hair shafts of the face and neck. The affected skin was congested, partially blanching on diascopy and bloody liquid was oozing from the follicular openings. Urticaria, dermographism and hypertension were excluded, the complete blood count and coagulation profile were within the reference ranges and an analysis of the bloody exudate confirmed its blood components. The cutaneous bleeding of the dog followed a self-limited course, with no episodes during the last two years. Clinical and laboratory findings and the long-term evolution of this dog bear striking similarities to haematidrosis, a rare human disease of multifactorial aetiology and equivocal pathogenesis.

Drug-Drug Interactions in Vestibular Diseases, Clinical Problems, and Medico-Legal Implications

Peripheral vestibular disease can be treated with several approaches (e.g., maneuvers, surgery, or medical approach). Comorbidity is common in elderly patients, so polytherapy is used, but it can generate the development of drug-drug interactions (DDIs) that play a role in both adverse drug reactions and reduced adherence. For this reason, they need a complex kind of approach, considering all their individual characteristics. Physicians must be able to prescribe and deprescribe drugs based on a solid knowledge of pharmacokinetics, pharmacodynamics, and clinical indications. Moreover, full information is required to reach a real therapeutic alliance, to improve the safety of care and reduce possible malpractice claims related to drug-drug interactions. In this review, using PubMed, Embase, and Cochrane library, we searched articles published until 30 August 2021, and described both pharmacokinetic and pharmacodynamic DDIs in patients with vestibular disorders, focusing the interest on their clinical implications and on risk management strategies.

Drug Repositioning With an Anticancer Effect: Contributions to Reduced Cancer Incidence in Susceptible Individuals

Certain diseases and age groups are associated with a higher incidence of cancer. Cancer prevention can be achieved using repositioned drugs that have anticancer ability, thereby reducing the incidence of cancer in susceptible individuals. This implies that the selection of repositioned drugs can have dual benefits: controlling pre-existing diseases and facilitating cancer prevention. This report outlines the rationale underlying drug repositioning for medications with an anticancer effect and discusses its advantages. We discuss repositioned drugs with anticancer effects that may contribute to cancer prevention in susceptible individuals and the general population with temporary, treatable conditions. The discussion of drug repositioning in this review should facilitate the initiation of clinical trials and lead to therapeutic application of such drugs to reduce the incidence of cancer in susceptible individuals.

First screening of biocides, persistent organic pollutants, pharmaceutical and personal care products in Antarctic phytoplankton from Deception Island by FT-ICR-MS

In recent years, the Antarctic territory has seen a rise in the number of tourists and scientists. This has led to an increase in the anthropogenic footprint in Antarctic ecosystems, namely in terms of emerging contaminants, such as Biocides, Persistent Organic Pollutants (POPs) as well as Pharmaceutical and Personal Care Products (PPCPs). Yet scarce information on the presence of these emerging contaminants is available for trophic compartments, especially the phytoplankton community. Using high resolution Fourier-transform ion cyclotron-resonance mass spectrometry (FT-ICR-MS), an untargeted screening of the metabolome of the phytoplankton community was performed. Seventy different contaminant compounds were found to be present in phytoplankton collected at two sites in Port Foster Bay at Deception Island. These emerging contaminants included 1 polycyclic aromatic hydrocarbon (PAH), 10 biocides (acaricides, fungicides, herbicides, insecticides and nematicides), 11 POPs (flame retardants, paints and dyes, polychlorinated biphenyl (PCB), phthalates and plastic components), 5 PCPs (cosmetic, detergents and dietary compounds), 40 pharmaceutical compounds and 3 illicit drugs. Pharmaceutical compounds were, by far, the largest group of emerging contaminants found in phytoplankton cells (anticonvulsants, antihypertensives and beta-blockers, antibiotics, analgesic and anti-inflammatory drugs). The detection of several of these potentially toxic compounds at the basis of the marine food web has potentially severe impacts for the whole ecosystem trophic structure. Additionally, the present findings also point out that the guidelines proposed by the Antarctic Treaty and Protocol on Environmental Protection to the Antarctic Treaty should be revisited to avoid the proliferation of these and other PPCPs in such sensitive environments.

Metabolic diversity as a reason for unsuccessful detoxification from benzodiazepines: the rationale for serum BZD concentration monitoring

PURPOSE

Many harms secondary to benzodiazepine (BZD) dependence force users towards detoxification treatment. However, even strongly motivated patients tolerate the process badly or experience early relapse. The detoxification procedure has not yet been standardized. The objective of this paper is to examine the hypothesis that faulty detoxification routines may have caused some failures.

METHODS

The detoxification approaches found in the literature were compared stage by stage. The review was used to identify possible common, across-the-board systematic errors.

RESULTS

The presented literature review confirms that the widespread divergence in the BZD metabolism rate is effectively neglected during detoxification routines. Without laboratory measurements, these differences, additionally interfered with by auxiliary drugs, undermine not only the scheduled but even the symptom-driven procedures. An initial substitution with a long-acting BZD, although recommended, may lead to over-accumulation. This excess, varying between patients and incompatible with the current tapering stage, may lead to repeated overestimation of the patient's adjustments to reduced doses. Consequently, the patient's good clinical presentation at withdrawal, resulting in a conclusion of detoxification, may actually reflect a persistently high serum BZD concentration. The low-concentration stage, if shifted past the end of treatment, exposes patients to unexpected, unassisted withdrawal crises. With laboratory feedback, these crises, unlike the symptoms related to deficient re-adaptation mechanisms, could be prevented. Moreover, by minimizing the high-concentration phase, time can be saved for properly assisted low-concentration challenges.

CONCLUSION

A customized detoxification procedure driven not only by the intensity of withdrawal symptoms but also by serum BZD monitoring may prevent some failures. As the standard regimen, it would make detoxification from BZDs more reliable and effective.

Enantiomeric Resolution and Absolute Configuration of a Chiral δ-Lactam, Useful Intermediate for the Synthesis of Bioactive Compounds

During the past several years, the frequency of discovery of new molecular entities based on γ- or δ-lactam scaffolds has increased continuously. Most of them are characterized by the presence of at least one chiral center. Herein, we present the preparation, isolation and the absolute configuration assignment of enantiomeric 2-(4-bromophenyl)-1-isobutyl-6-oxopiperidin-3-carboxylic acid (trans-1). For the preparation of racemic trans-1, the Castagnoli-Cushman reaction was employed. (Semi)-preparative enantioselective HPLC allowed to obtain enantiomerically pure trans-1 whose absolute configuration was assigned by X-ray diffractometry. Compound (+)-(2R,3R)-1 represents a reference compound for the configurational study of structurally related lactams.

Benzodiazepine-Related Cognitive Impairment or Dementia: A Signal Detection Study Using a Case/Non-Case Approach

OBJECTIVE

The association between benzodiazepine use and the risk of cognitive impairment or dementia has been controversial. Our study aims to detect this association through a case/non-case method using the Korea Institute of Drug Safety & Risk Management-Korea adverse event reporting system database (KIDS-KD) between 2007 and 2016.

METHODS

Cases were adverse event (AE)-pairs with suspected cognitive impairment or dementia. 10 non-cases were matched to each case on age and sex. Exposure was defined as use of benzodiazepines, including long-, intermediate-, and short-acting benzodiazepine. We conducted multivariable logistic regression analyses to estimate reporting odds ratios (ROR) and 95% confidence intervals (CI).

RESULTS

Of the 1,086,584 AE-pairs, 887 cases were suspected AE-pairs of cognitive impairment or dementia, and 775,444 non-cases were selected. Benzodiazepine use was associated with increased AE-pairs of cognitive impairment or dementia when assessed using those with certain, probable, and/or possible in causality assessments (ROR=2.69, 95% CI=1.66-4.38). Higher ROR estimates were shown in female (2.33, 1.48-3.67) and in those with polypharmacy (2.20, 1.35-3.57). Dementia safety profiles were inconsistent across individual benzodiazepine components.

CONCLUSION

These results suggest the potentially increased association between benzodiazepine use and cognitive impairment or dementia in female and those with polypharmacy. Inconsistent safety profiles of benzodiazepine components should be further investigated.

Risk factors for severe opioid-induced respiratory depression in hospitalized adults: A case-control study

Background: Opioids are commonly prescribed to hospitalized adults to promote adequate pain relief, yet they can cause potentially fatal respiratory depression.

Aim: The aim of this study was to examine the risk factors for the development of severe opioid-induced respiratory depression (OIRD) in hospitalized adults to ensure adequate monitoring of high-risk patients.

Methods: A retrospective case–control study was conducted using data from the medical records of a university-affiliated hospital in Canada. Cases were eligible if they were adults (≥18 years old) and received opioid analgesia within 24 h of naloxone administration for respiratory depression. Controls had the same eligibility criteria, except for respiratory depression and naloxone administration. The case–control ratio was 1:1, and they were matched based on sex, type of unit, opioid molecule and the presence/absence of medication errors.

Results: A total of 133 cases and 133 controls were included. Following cumulative risk factor analysis, renal failure (odds ratio [OR] = 2.176, 95% confidence interval [CI], 1.021–4.640, P = 0.044), the first 24 h of opioid administration (OR = 1.899, 95% CI, 1.090–3.309, P = 0.024), concomitant central nervous system (CNS) depressants (OR = 1.785, 95% CI, 1.023–3.113, P = 0.041), and increasing age (OR = 1.019, 95% CI, 1.002–1.035, P = 0.028) were positively associated with severe OIRD.

Conclusions: Some adult hospitalized patients were at higher risk of experiencing severe OIRD, such as those with renal failure, those in their first 24 h of opioid administration, those receiving CNS depressants in addition to opioids, and those with an advanced age. These results will assist with the screening of patients at higher risk for severe OIRD, which is key to implementing appropriate monitoring and enhancing the safety of opioid use in hospital settings.

High-Dose Dependence and Cognitive Side Effects to Medical Prescription of Etizolam

Introduction: The use of novel designer drugs has increased worldwide over the years. Etizolam is a designer benzodiazepine (BZD) that has raised concern because of its growing non-medical use, liability to tolerance and dependence, and related harms. Studies exploring the abuse liability and cognitive effects of etizolam outside the therapeutic doses are lacking. Aims: To explore the abuse liability of etizolam and the characteristics of patients affected by etizolam high-dose dependence in a nationwide tertiary referral addiction unit. To document the cognitive changes to etizolam high-dose use. Design and Methods: Sociodemographic and clinical data on subjects with etizolam high-dose use were retrospectively collected from a database of 1,293 patients consecutively admitted to the Addiction Medicine Unit, Verona University Hospital, Italy for detoxification from high-dose BZDs or Z-drugs dependence. Thorough neuropsychological testing explored the cognitive side effects of high-dose etizolam use. Results: We found eleven etizolam high-dose users, of which eight used etizolam only, and three used etizolam with other BZDs/zolpidem. All the patients were prescribed etizolam for medical reasons, i.e., anxiety and/or insomnia. Neuropsychological evaluation showed deficits of working memory, visuospatial memory and executive function in a 27-year-old woman who used etizolam 15 mg daily. Discussion: Our findings suggest that abuse and dependence liability of etizolam should be considered a public health and social problem. They offer preliminary evidence on the cognitive side effects of etizolam high-dose use. Conclusions: This report offers new information on the potential harms of etizolam in patients who are prescribed this drug for medical reasons.

Development of 1,3-thiazole analogues of imidazopyridines as potent positive allosteric modulators of GABAA receptors

Structure-activity relationship studies were conducted in the search for 1,3-thiazole isosteric analogs of imidazopyridine drugs (Zolpidem, Alpidem). Three series of novel γ-aminobutyric acid receptor (GABA_AR) ligands belonging to imidazo[2,1-b]thiazoles, imidazo[2,1-b][1,3,4]thiadiazoles, and benzo[d]imidazo[2,1-b]thiazoles were synthesized and characterized as active agents against GABA_AR benzodiazepine-binding site. In each of these series, potent compounds were discovered using a radioligand competition binding assay. The functional properties of highest-affinity compounds 28 and 37 as GABA_AR positive allosteric modulators (PAMs) were determined by electrophysiological measurements. In vivo studies on zebrafish demonstrated their potential for the further development of anxiolytics. Using the OECD "Fish, Acute Toxicity Test" active compounds were found safe and non-toxic. Structural bases for activity of benzo[d]imidazo[2,1-b]thiazoles were proposed using molecular docking studies. The isosteric replacement of the pyridine nuclei by 1,3-thiazole, 1,3,4-thiadiazole, or 1,3-benzothiazole in the ring-fused imidazole class of GABA_AR PAMs was shown to be promising for the development of novel hypnotics, anxiolytics, anticonvulsants, and sedatives drug-candidates.

Psychopharmacology and Cardiovascular Disease

This review discusses common mental health disorders and their associations with cardiovascular disease risks. Commonly found mental health disorders include depression, anxiety, and personality types. The link between depression and cardiovascular disease mortality has been established. Depression is also common in patients with heart failure. In addition to discussing psychological disorders, a review of psychotropic drugs is also included. Drugs are described for therapy for depression and anxiety, as well as associations with cardiovascular drug-drug interactions. Drug-drug interactions are more common and potentially dangerous in elderly patients, in whom the conditions often coexist. The most common drug-drug interactions involve the P450 system of enzymes.

Is etizolam a safe medication? Effects on psychomotor perfomance at therapeutic dosages of a newly abused psychoactive substance

Etizolam is a drug from the thienotriazoldiazepine class, widely prescribed as anxiolytic due to its apparently secure toxicological profile. Nevertheless, some recent cases of etizolam dependence, intoxications and fatalities associated to its abuse have been reported in the international literature. For this reason, the drug listed as new psychoactive substance (NPS) by the World Health Organization (WHO) since 2015. Euphoric effect at high dosage is the first cause of its recreational use that has determined a wider distribution in the illicit market. An experimental study was performed to obtain evidence that etizolam at low therapeutic dosages is a drug with negligible influence on the psychomotor performances involved in driving. The psychomotor performance was assessed by performing different tests, such as critical tracking task (CTT), critical flicker fusion (CFF), choice reaction time (CRT), visual vigilance task (VVT), response competition test (RCT) in a group of 16 healthy volunteers after a single administration of etizolam at two different dosages (0.25 mg or 1.00 mg) in comparison to placebo. The test results showed that etizolam at 0.25 mg and 1.00 mg had no significant effect on vigilance, short term memory, psychomotor coordination or speed in decision making. Differently, abuse of etizolam to obtain the euphoric effects at presumably high dosages or in combination with other psychoactive substances could be fatal. The negligible side effects on mental and behavioral function demonstrated by this study, could represent an incitement to abuse, which can be strongly discouraged with correct information on differences between its correct use and its misuse.

First evaluation of the possibility of testing for drugged driving using exhaled breath sampling

Objective: Driving under the influence of psychoactive drugs causes an increased risk for accidents. In combating this, sobriety tests at the roadside are common practice in most countries. Sampling of blood and urine for forensic investigation cannot be done at the roadside and poses practical problems associated with costs and time. An alternative specimen for roadside testing is therefore warranted and the aerosol particles in exhaled breath are one such alternative. Methods: The present study investigated how the exhaled breath sample compared with the routine legal investigations of blood and urine collected from suspects of drugged driving at 2 locations in Sweden. Exhaled breath was collected using a simple filter collection device and analyzed with state-of-the-art mass spectrometry technique. Results: The total number of cases used for this investigation was 67. In 54 of these cases (81%) the results regarding a positive or negative drug test result agreed and in 13 they disagreed. Out of these, the report from the forensic investigation of blood/urine was negative in 21 cases. In 6 of these, analytical findings were made in exhaled breath and these cases were dominated by the detection of amphetamine. In 7 cases a positive drug test from the forensic investigation was not observed in the breath sample and these cases were dominated by detection of tetrahydrocannabinol in blood. In total, 45 samples were positive with breath testing and the number of positives with established forensic methods was 46. Conclusion: The promising results from this study provide support to exhaled breath as a viable specimen for testing of drugged driving. The rapid, easy, and convenient sampling procedure offers the possibility to collect a drug test specimen at the roadside. The analytical investigation must be done in a laboratory at present because of the need for a highly sensitive instrument, which is already in use in forensic laboratories. The analytical work is not more challenging than for blood or oral fluid and should not cause an increase in cost. However, more studies need to be done before exhaled breath drug testing can be applied routinely for drugged driving investigation.

Gabapentin and pregabalin to treat aggressivity in dementia: a systematic review and illustrative case report

AIMS

The prevalence of dementia is rising as life expectancy increases globally. Behavioural and psychological symptoms of dementia (BPSD), including agitation and aggression, are common, presenting a challenge to clinicians and caregivers.

METHODS

Following PRISMA guidelines, we systematically reviewed evidence for gabapentin and pregabalin against BPSD symptoms of agitation or aggression in any dementia, using six databases (Pubmed, CINHL, PsychINFO, HealthStar, Embase, and Web of Science). Complementing this formal systematic review, an illustrative case of a patient with BPSD in mixed Alzheimer's/vascular dementia, who appeared to derive benefits in terms of symptom control and functioning from the introduction of gabapentin titrated up to 3600 mg day^-1 alongside other interventions, is presented.

RESULTS

Twenty-four relevant articles were identified in the systematic review. There were no randomized trials. Fifteen papers were original case series/case reports of patients treated with these compounds, encompassing 87 patients given gabapentin and six given pregabalin. In 12 of 15 papers, drug treatment was effective in the majority of cases. The remaining nine papers were solely reviews, of which two were described as systematic but predated PRISMA guidelines. Preliminary low-grade evidence based on case series and case reviews suggests possible benefit of gabapentin and pregabalin in patients with BPSD in Alzheimer's disease. These benefits cannot be confirmed until well-powered randomized controlled trials are undertaken. Evidence in frontotemporal dementia is lacking.

CONCLUSION

Gabapentin and pregabalin could be considered for BPSD when medications having stronger evidence bases (risperidone, other antipsychotics, carbamazepine and citalopram) have been ineffective or present unacceptable risks of adverse outcomes.

Lorazepam as a Cause of Drug-Induced Liver Injury

Lorazepam is a benzodiazepine derivative that is globally used for the therapy of anxiety and insomnia. A 51-year-old Japanese man with yellowish discoloration of the eyes and skin and pruritus was admitted due to liver dysfunction. He had taken lorazepam approximately 5 months prior to this admission. The clinical presentation and pathologic findings in the liver were consistent with drug-induced liver injury. After cessation of lorazepam, treatment with Stronger neo-minophagen C and ursodeoxycholic acid was started, and his liver injury resolved after 59 days. This case must serve as a warning to physicians to be aware of the possibility of unexpected liver injury caused by lorazepam.

Challenges and common weaknesses in case-control studies on drug use and road traffic injury based on drug testing of biological samples

PURPOSE

To determine and discuss common weaknesses and errors in case-control studies on the association between drug use and road traffic crash injury among drivers and recommend improvements for future studies.

METHODS

A search for case-control studies published between 2000 and 2016 was performed using PubMed and other databases in addition to manual search. The used methodologies were compared with requirements and recommendations for case-control studies as well as current knowledge on the interpretation of drug concentrations in biological samples.

RESULTS

Seventeen studies were identified. The major difficulties in the studies were related to likely selection bias, information bias, and confounding. In some studies, the definition of drug exposure was different for controls than for cases, generating potentially serious errors in the odds ratio estimations. Other weaknesses include lacking explanation of the assessment of drug exposure, missing covariates, lacking description of statistical methods, and lack of discussion of bias and confounding.

CONCLUSIONS

Many of the observed challenges and weaknesses can be overcome or reduced. Recommendations for future studies are presented.

Diazepam fails to alter anxiety-like responses but affects motor function in a white-black test paradigm in larval zebrafish (Danio rerio)

The growing popularity of zebrafish in psychopharmacology and behavioral brain research is partly due to the practicality and simplicity of drug administration in this species. Several drugs may be administered to zebrafish by immersing the fish in the drug solution. Furthermore, numerous drugs developed for mammals, including humans, have been found to show a similar effect profile in the zebrafish. Thus, the zebrafish has been suggested as a potentially useful animal screening tool. Despite decades of drug development, anxiety still represents a major unmet medical need, and the search for anxiolytic compounds is continuing. The zebrafish has been proposed for high throughput screens for anxiolytic compounds, and the effects of anxiolytic compounds on the behavior of zebrafish have started to be explored. Diazepam (Valium®) is a frequently prescribed human anxiolytic, a GABA_A receptor agonist, has also started to be tested in zebrafish, but with occasional contradicting results. Here, we investigate the effects of diazepam in larval (6-day post-fertilization old) zebrafish in a black-white preference paradigm. We found significant white preference and thigmotaxis (edge preference) in our control fish, anxiety-like responses that habituated over time. However, unexpectedly, we observed no anxiolytic effects of diazepam on these behaviors, and only detected significant motor activity reducing effect of the drug. We discuss the complex interpretation of light/dark tests in zebrafish, and also speculate about the possibility of differential GABAergic mechanisms that diazepam affects in larval vs adult zebrafish.

Conversion factors for assessment of driving impairment after exposure to multiple benzodiazepines/z-hypnotics or opioids

AIMS

Norway has introduced legal concentration limits in blood for 28 non-alcohol drugs in driving under the influence cases. As of 2016 this legislation also regulates the assessment of combined effects of multiple benzodiazepines and opioids. We herein describe the employed methodology for the equivalence tables for concentrations of benzodiazepines/z-hypnotics and opioids implemented in the Norwegian Road Traffic Act.

METHODS

Legislative limits corresponding to impairment at blood alcohol concentrations (BAC) of 0.02%, 0.05% and 0.12% were established for 15 different benzodiazepines and opioids. This was based on a concept of a linear relationship between blood drug concentration and impairment in drug naïve users. Concentration ratios between these drugs were used to establish conversion factors and calculate net impairment using diazepam and morphine equivalents.

RESULTS

Conversion factors were established for 14 benzodiazepines/z-hypnotics (alprazolam, bromazepam, clobazam, clonazepam, etizolam, flunitrazepam, lorazepam, nitrazepam, nordiazepam, oxazepam, phenazepam, temazepam, zolpidem and zopiclone) and two opioids (methadone and oxycodone).

CONCLUSIONS

Conversion factors to calculate diazepam and morphine equivalents for benzodiazepines/z-hypnotics and selected opioids, respectively, have been operative in the Norwegian Road Traffic Act as of February 2016. Calculated equivalents can be applied by the courts to meter out sanctions.

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.

Time-dependent interacting effects of caffeine, diazepam, and ethanol on zebrafish behaviour

Zebrafish have become a popular animal model for behavioural pharmacology due to their small size, rapid development, and amenability to high throughput behavioural drug screens. Furthermore, water-soluble compounds can be administered via immersion of the fish in the drug solution, which provides a non-invasive drug delivery method. Numerous studies have demonstrated stimulant effects of alcohol. Diazepam and caffeine, on the other hand have been found to have inhibitory effect on locomotor activity in zebrafish. However, the time-dependent changes induced by these psychoactive drugs are rarely reported, and potential drug interactions have not been examined in zebrafish, despite the translational relevance of this question. In the current study, we examine time- and dose-dependent changes in zebrafish following exposure to caffeine, diazepam, and ethanol quantifying four different behavioural parameters over a 30min recording session. We subsequently analyze potential drug-drug interactions by co-administering the three drugs in different combinations. Our time-course and dose-response analyses for each of the three drugs represent so far the most detailed studies available serving as a foundation for future psychopharmacology experiments with zebrafish. Furthermore, we report significant interactions between the three drugs corroborating findings obtained with rodent models as well as in humans, providing translational relevance for the zebrafish model.

Effects of 25 mg oxazepam on emotional mimicry and empathy for pain: a randomized controlled experiment

Emotional mimicry and empathy are mechanisms underlying social interaction. Benzodiazepines have been proposed to inhibit empathy and promote antisocial behaviour. First, we aimed to investigate the effects of oxazepam on emotional mimicry and empathy for pain, and second, we aimed to investigate the association of personality traits to emotional mimicry and empathy. Participants (n=76) were randomized to 25 mg oxazepam or placebo. Emotional mimicry was examined using video clips with emotional expressions. Empathy was investigated by pain stimulating the participant and a confederate. We recorded self-rated experience, activity in major zygomatic and superciliary corrugator muscles, skin conductance, and heart rate. In the mimicry experiment, oxazepam inhibited corrugator activity. In the empathy experiment, oxazepam caused increased self-rated unpleasantness and skin conductance. However, oxazepam specifically inhibited neither emotional mimicry nor empathy for pain. Responses in both experiments were associated with self-rated empathic, psychopathic and alexithymic traits. The present results do not support a specific effect of 25 mg oxazepam on emotional mimicry or empathy.

Effects of 25 mg oxazepam on emotional mimicry and empathy for pain: a randomized controlled experiment

Emotional mimicry and empathy are mechanisms underlying social interaction. Benzodiazepines have been proposed to inhibit empathy and promote antisocial behaviour. First, we aimed to investigate the effects of oxazepam on emotional mimicry and empathy for pain, and second, we aimed to investigate the association of personality traits to emotional mimicry and empathy. Participants (n=76) were randomized to 25 mg oxazepam or placebo. Emotional mimicry was examined using video clips with emotional expressions. Empathy was investigated by pain stimulating the participant and a confederate. We recorded self-rated experience, activity in major zygomatic and superciliary corrugator muscles, skin conductance, and heart rate. In the mimicry experiment, oxazepam inhibited corrugator activity. In the empathy experiment, oxazepam caused increased self-rated unpleasantness and skin conductance. However, oxazepam specifically inhibited neither emotional mimicry nor empathy for pain. Responses in both experiments were associated with self-rated empathic, psychopathic and alexithymic traits. The present results do not support a specific effect of 25 mg oxazepam on emotional mimicry or empathy.

Benzodiazepine Use During Hospitalization: Automated Identification of Potential Medication Errors and Systematic Assessment of Preventable Adverse Events

Objective

Benzodiazepines and “Z-drug” GABA-receptor modulators (BDZ) are among the most frequently used drugs in hospitals. Adverse drug events (ADE) associated with BDZ can be the result of preventable medication errors (ME) related to dosing, drug interactions and comorbidities. The present study evaluated inpatient use of BDZ and related ME and ADE.

Methods

We conducted an observational study within a pharmacoepidemiological database derived from the clinical information system of a tertiary care hospital. We developed algorithms that identified dosing errors and interacting comedication for all administered BDZ. Associated ADE and risk factors were validated in medical records.

Results

Among 53,081 patients contributing 495,813 patient-days BDZ were administered to 25,626 patients (48.3%) on 115,150 patient-days (23.2%). We identified 3,372 patient-days (2.9%) with comedication that inhibits BDZ metabolism, and 1,197 (1.0%) with lorazepam administration in severe renal impairment. After validation we classified 134, 56, 12, and 3 cases involving lorazepam, zolpidem, midazolam and triazolam, respectively, as clinically relevant ME. Among those there were 23 cases with associated adverse drug events, including severe CNS-depression, falls with subsequent injuries and severe dyspnea. Causality for BDZ was formally assessed as ‘possible’ or ‘probable’ in 20 of those cases. Four cases with ME and associated severe ADE required administration of the BDZ antagonist flumazenil.

Conclusions

BDZ use was remarkably high in the studied setting, frequently involved potential ME related to dosing, co-medication and comorbidities, and rarely cases with associated ADE. We propose the implementation of automated ME screening and validation for the prevention of BDZ-related ADE.

Effects of Prereactivation Propranolol on Cocaine Craving Elicited by Imagery Script/Cue Sets in Opioid-dependent Polydrug Users: A Randomized Study

OBJECTIVES

Relapse to drug misuse may follow exposure to drug cues that elicit craving. The learned associations, or "emotional memories," that underlie responses to cues may be attenuated or erased by the β-adrenergic antagonist propranolol during a "reconsolidation window" shortly after the memories are reactivated by cues.

METHODS

We evaluated the effects of propranolol on cue-induced drug cravings in healthy opioid-dependent individuals who used cocaine while receiving methadone maintenance (n = 33). Participants were asked to recall specific cocaine use and neutral events in an interview; these events were used to develop personalized auditory script/cue sets. Approximately 1 week later, propranolol (40 mg) or placebo (random assignment, double blind) was administered orally before presentation of the script/cue sets; the presentation of the script/cue sets were tested 1 week and 5 weeks after the propranolol/placebo session. Ongoing drug use was monitored via urine screens and self-report in twice-weekly visits.

RESULTS

Cue reactivity, as assessed by craving scales and physiological responses, was unexpectedly greater in the propranolol group than in the placebo group. This counterhypothesized group difference was present acutely during propranolol administration and seemed to persist (without reaching statistical significance) during the subsequent test sessions.

CONCLUSIONS

Our results do not support the use of propranolol for cue-induced cocaine craving in opioid-maintained patients.

A pilot study of serotonin-1A receptor genotypes and rapid eye movement sleep sensitivity to serotonergic/cholinergic imbalance in humans: a pharmacological model of depression

RATIONALE

The serotonergic and cholinergic systems are jointly involved in regulating sleep but this system is theorized to be disturbed in depressed individuals. We previously reported that cholinergic and serotonergic agents induce sleep changes partially consistent with monoamine models of sleep disturbances in depression. One potential cause of disturbed neurotransmission is genetic predisposition. The G(-1019) allele of the serotonin-1A (5-HT1A) receptor promoter region predicts an increased risk for depression compared to the wild-type C(-1019) allele.

OBJECTIVE

The goal of this study was to investigate how serotonin-1A receptor genotypes mediate sleep sensitivity to pharmacological probes modeling the serotonergic/cholinergic imbalance of depression.

METHODS

Seventeen healthy female participants homozygous for either C (n=11) or G (n=6) alleles aged 18-27 years were tested on four nonconsecutive nights. Participants were given galantamine (an anti-acetylcholinesterase), buspirone (a serotonergic agonist), both drugs together, or placebos before sleeping.

RESULTS

As reported previously, buspirone significantly increased rapid eye movement (REM) latency (P<0.001), as well as awakenings, percentage of time spent awake, and percentage of time asleep spent in stage N1 (P<0.019). Galantamine increased awakenings, percentage of time spent awake, percentage of time asleep spent in stage N1, and percentage of time asleep spent in REM, and decreased REM latency and percentage of time asleep spent in stage N3 (P<0.019). Galantamine plus buspirone given together disrupted sleep more than either drug alone, lowering sleep efficiency and percentage of time asleep spent in stage N3 and increasing awakenings, percentage of time spent awake, and percentage of time asleep spent in stage N1 (P<0.019). There was no main effect of genotype nor was there a significant multivariate interaction between genotype and drug condition.

CONCLUSION

These findings are partially consistent with the literature about sleep in depression, notably short REM latency, higher percentage of total sleep time spent in REM, lower percentage of time asleep spent in stage N3, and increased sleep fragmentation. The C/G mutation in the serotonin-1A receptor promoter region does not appear to cause noticeable differences in the sleep patterns of a relatively small sample of healthy young females. Future studies with larger sample sizes are required.

The effects of galantamine and buspirone on sleep structure: Implications for understanding sleep abnormalities in major depression

RATIONALE

The serotonergic and cholinergic systems are jointly involved in regulating sleep, but this balance is theorized to be disturbed in depressed individuals.

OBJECTIVE

The goal of this study was to use biological probes in healthy participants, to model the serotonergic/cholinergic imbalance of depression and its associated abnormalities in sleep structure.

METHODS

We tested 20 healthy female participants 18-30 years of age on four non-consecutive nights. Participants were given galantamine (a cholinergic agent), buspirone (a serotonergic agonist), both drugs together, or placebo before sleeping.

RESULTS

Buspirone suppressed tonic rapid eye movement (REM): There was a significant increase in REM latency (p < 0.001). Galantamine increased tonic REM sleep, leading to more time spent in REM (p < 0.001) and shorter REM latency (p < 0.01). Galantamine and buspirone given together were not significantly different from the placebo night by REM sleep measures, but disrupted sleep more than either drug alone.

CONCLUSIONS

These findings are partially consistent with the cholinergic literature about sleep in depression, notably short REM latency, higher percentage of total sleep time spent in REM and increased sleep fragmentation. The prolonged REM latency and reduced percentage of REM with buspirone resembled the effect of selective serotonin reuptake inhibitor antidepressants on REM sleep.

Prototypical anxiolytics do not reduce anxiety-like behavior in the open field in C57BL/6J mice

Understanding and effectively treating anxiety disorders are a challenge for both scientists and clinicians. Despite a variety of available therapies, the efficacy of current treatments is still not optimal and adverse side effects can result in non-compliance. Animal models have been useful for studying the underlying biology of anxiety and assessing the anxiolytic properties of potential therapeutics. The open field (OF) is a commonly used assay of anxiety-like behavior. The OF was developed and validated in rats and then transferred to use in the mouse with only limited validation. The present study tests the efficacy of prototypical benzodiazepine anxiolytics, chlordiazepoxide (CDP) and diazepam (DZ), for increasing center time in the OF in C57BL/6J (B6) mice. Multiple doses of CDP and DZ did not change time spent in the center of the OF. Increasing illumination in the OF did not alter these results. The non-benzodiazepine anxiolytic, buspirone (BUSP) also failed to increase center time in the OF while the anxiogenic meta-chlorophenylpiperazine (mCPP) increased center time. Additional inbred mouse strains, BALB/cJ (BALB) and DBA/2J (D2) did not show any change in center time in response to CDP. Moreover, evaluation of CDP in B6 mice in the elevated plus maze (EPM), elevated zero maze (EZM) and light dark assay (LD) did not reveal changes in anxiety-like behavior while stress-induced hyperthermia (SIH) was decreased by DZ. Pharmacokinetic (PK) studies suggest that adequate CDP is present to induce anxiolysis. We conclude that the measure of center time in the OF does not show predictive validity for anxiolysis in these inbred mouse strains.

Sensitization of neurons in the central nucleus of the amygdala via the decreased GABAergic inhibition contributes to the development of neuropathic pain-related anxiety-like behaviors in rats

BACKGROUND

Despite high prevalence of anxiety accompanying with chronic pain, the mechanisms underlying pain-related anxiety are largely unknown. With its well-documented role in pain and emotion processing, the amygdala may act as a key player in pathogenesis of neuropathic pain-related anxiety. Pain-related plasticity and sensitization of CeA (central nucleus of the amygdala) neurons have been shown in several models of chronic pain. In addition, firing pattern of neurons with spike output can powerfully affect functional output of the brain nucleus, and GABAergic neurons are crucial in the modulation of neuronal excitability. In this study, we first investigated whether pain-related plasticity (e.g. alteration of neuronal firing patterns) and sensitization of CeA neurons contribute to nerve injury-evoked anxiety in neuropathic rats. Furthermore, we explored whether GABAergic disinhibition is responsible for regulating firing patterns and intrinsic excitabilities of CeA neurons as well as for pain-related anxiety in neuropathic rats.

RESULTS

We discovered that spinal nerve ligation (SNL) produced neuropathic pain-related anxiety-like behaviors in rats, which could be specifically inhibited by intra-CeA administration of anti-anxiety drug diazepam. Moreover, we found potentiated plasticity and sensitization of CeA neurons in SNL-induced anxiety rats, of which including: 1) increased burst firing pattern and early-adapting firing pattern; 2) increased spike frequency and intrinsic excitability; 3) increased amplitude of both after-depolarized-potential (ADP) and sub-threshold membrane potential oscillation. In addition, we observed a remarkable reduction of GABAergic inhibition in CeA neurons in SNL-induced anxiety rats, which was proved to be important for altered firing patterns and hyperexcitability of CeA neurons, thereby greatly contributing to the development of neuropathic pain-related anxiety. Accordantly, activation of GABAergic inhibition by intra-CeA administration of muscimol, a selective GABAA receptors agonist, could inhibit SNL-induced anxiety-like behaviors in neuropathic rats. By contrast, suppression of GABAergic inhibition by intra-CeA administration of bicuculline, a selective GABAA receptors antagonist, produced anxiety-like behavior in normal rats.

CONCLUSIONS

This study suggests that reduction of GABAergic inhibition may be responsible for potentiated plasticity and sensitization of CeA neurons, which likely underlie the enhanced output of amygdala and neuropathic pain-related anxiety in SNL rats.

Influence of aripiprazole, risperidone, and amisulpride on sensory and sensorimotor gating in healthy 'low and high gating' humans and relation to psychometry

Despite advances in the treatment of schizophrenia spectrum disorders with atypical antipsychotics (AAPs), there is still need for compounds with improved efficacy/side-effect ratios. Evidence from challenge studies suggests that the assessment of gating functions in humans and rodents with naturally low-gating levels might be a useful model to screen for novel compounds with antipsychotic properties. To further evaluate and extend this translational approach, three AAPs were examined. Compounds without antipsychotic properties served as negative control treatments. In a placebo-controlled, within-subject design, healthy males received either single doses of aripiprazole and risperidone (n=28), amisulpride and lorazepam (n=30), or modafinil and valproate (n=30), and placebo. Prepulse inhibiton (PPI) and P50 suppression were assessed. Clinically associated symptoms were evaluated using the SCL-90-R. Aripiprazole, risperidone, and amisulpride increased P50 suppression in low P50 gaters. Lorazepam, modafinil, and valproate did not influence P50 suppression in low gaters. Furthermore, low P50 gaters scored significantly higher on the SCL-90-R than high P50 gaters. Aripiprazole increased PPI in low PPI gaters, whereas modafinil and lorazepam attenuated PPI in both groups. Risperidone, amisulpride, and valproate did not influence PPI. P50 suppression in low gaters appears to be an antipsychotic-sensitive neurophysiologic marker. This conclusion is supported by the association of low P50 suppression and higher clinically associated scores. Furthermore, PPI might be sensitive for atypical mechanisms of antipsychotic medication. The translational model investigating differential effects of AAPs on gating in healthy subjects with naturally low gating can be beneficial for phase II/III development plans by providing additional information for critical decision making.