The effects of single dose anxiolytic medication on the CO2 models of anxiety: differentiation of subjective and objective measures

The Use of β-Adrenergic Receptor Antagonists in Psychiatry: A Review

BACKGROUND

β-Blockers (BBs) are a widely used class of medications with a number of medical indications. Their ability to suppress the adrenergic response has made them a target of investigation for treating a variety of psychiatric symptoms.

OBJECTIVE

The aim of this review is to identify evidence regarding the use of BBs for various psychiatric disorders including anxiety disorders, mood disorders, psychosis, and posttraumatic stress disorder. We also review the evidence for use for aggression and agitation and for extrapyramidal side effects of psychiatric medications.

METHODS

A search of PubMed and Google Scholar was conducted with search terms relevant to the use of BBs for psychiatric conditions. Studies were selected based on relevance to the review objective, focusing on systematic reviews and meta-analyses. Case reports were included and are clearly identified when referenced in this review.

RESULTS

A total of 44 publications were included that examined the use of BBs as treatment for the following psychiatric symptoms and conditions: anxiety disorders, depression and mood disorders, acute stress disorder and postraumatic stress disorder, psychotic disorders and extrapyramidal symptoms, as well as aggression and agitation. Additionally, adverse effects and drug-drug interactions were reviewed.

CONCLUSION

Well-characterized psychiatric uses of BBs include treating symptoms of performance anxiety and akathisia. Some positive evidence exists for BB therapy in other disorders such as specific phobia, panic disorder, and for aggression in patients with psychosis, acquired brain injury, or intellectual disability. Most of the evidence on the role of BBs in psychiatry is as adjunctive treatment for management of somatic symptoms rather than as monotherapy. Outside of performance anxiety and akathisia, the role of BBs in psychiatry has not been subjected to careful study, and further investigative trials are needed.

Multiple-dose clinical pharmacology of the selective orexin-1 receptor antagonist ACT-539313

AIMS

Compounds that selectively target orexin-1 receptors may be beneficial for the treatment of various disorders. The role of selective orexin-1 receptor antagonists (1-SORAs) in addictive behavior and stress/anxiety-related disturbances has been demonstrated in animals. ACT-539313, an orally active, potent 1-SORA, has been assessed in a clinical single-ascending dose study and exhibited good safety and tolerability. In the two reported studies on ACT-539313, multiple-dose pharmacokinetics (PK), pharmacodynamics (PD), safety, and tolerability were investigated and in a proof-of-mechanism study a CO₂ challenge was applied as pharmacological model for induction of anxiety and panic symptoms (sequential inhalation of air, 7.5% CO₂, and 35% CO₂).

METHODS

Two double-blind, placebo-controlled, randomized, multiple-dose studies included 58 healthy male and female subjects. In Study 1, multiple-ascending oral doses of 30, 100, and 200 mg twice daily (b.i.d.) ACT-539313 were investigated in 3 dose groups of 8 or 12 subjects (of whom 2 received placebo per dose group). Study 2 was conducted as a randomized two-way crossover design, enrolling 21 male and 9 female subjects who received 200 mg ACT-539313 or matching placebo b.i.d. for 2.5 days followed by a CO₂ challenge, with a washout period in between. PK, PD (objective and subjective measures of sedation, alertness, effects on central nervous system (CNS), and anxiety/panic symptoms), safety, and tolerability were assessed.

RESULTS

At steady state, ACT-539313 was rapidly absorbed with a median time to maximum plasma concentration of 1.8-2.3 h and eliminated with a mean half-life of 3.8-6.5 h. Overall exposure increased dose-proportionally. In Study 1, PD effects confirmed activity of ACT-539313 on the CNS, without consistent or marked effects of sedation, reduced alertness or visuo-motor impairment. In the CO₂ challenge, cortisol concentrations were lower during initial air inhalation after treatment with ACT-539313 compared to placebo, while no difference was detected after CO₂ inhalation. Trends for lower scores in subjective anxiety assessments were observed for ACT-539313. Besides reports of stress related to the challenge, the most frequently reported adverse events were somnolence and headache. No clinically relevant effects in other safety assessments were observed.

CONCLUSIONS

Multiple-dose administration of ACT-539313 was safe and well tolerated up to multiple doses of 200 mg b.i.d. The drug's PK properties as well as the pattern of a decrease in stress-related symptoms after the CO₂ challenge support further investigations of ACT-539313.

Modeling anxiety in healthy humans: a key intermediate bridge between basic and clinical sciences

Animal models of anxiety disorders are important for elucidating neurobiological defense mechanisms. However, animal models are limited when it comes to understanding the more complex processes of anxiety that are unique to humans (e.g., worry) and to screen new treatments. In this review, we outline how the Experimental Psychopathology approach, based on experimental models of anxiety in healthy subjects, can mitigate these limitations and complement research in animals. Experimental psychopathology can bridge basic research in animals and clinical studies, as well as guide and constrain hypotheses about the nature of psychopathology, treatment mechanisms, and treatment targets. This review begins with a brief review of the strengths and limitations of animal models before discussing the need for human models of anxiety, which are especially necessary to probe higher-order cognitive processes. This can be accomplished by combining anxiety-induction procedures with tasks that probe clinically relevant processes to identify neurocircuits that are potentially altered by anxiety. The review then discusses the validity of experimental psychopathology and introduces a methodological approach consisting of five steps: (1) select anxiety-relevant cognitive or behavioral operations and associated tasks, (2) identify the underlying neurocircuits supporting these operations in healthy controls, 3) examine the impact of experimental anxiety on the targeted operations in healthy controls, (4) utilize findings from step 3 to generate hypotheses about neurocircuit dysfunction in anxious patients, and 5) evaluate treatment mechanisms and screen novel treatments. This is followed by two concrete illustrations of this approach and suggestions for future studies.

The role of beta-adrenolytic drugs in treating anxiety disorders

Introduction: Beta blockers are mainly used in treating cardiovascular diseases. However, it has been observed that these drugs have also an anxiolytic potential. Over the years, a number of clinical trials have been conducted aimed at determining the effectiveness of beta blockers in treating anxiety disorders.

The aim of the article: The main objective of the article is to present the significance and position of adrenolytic drugs in the pharmacotherapy of anxiety disorders on the basis of available literature. Moreover, the authors also decided to take into account the data from current research results, considering the problem of side effects of using adrenolytic drugs - especially the controversial reports on their effect on the development of affective disorders.

Method: An analysis was conducted of articles from Medline/PubMed database, selected on the basis of the following key words: anxiety disorders, beta blockers, adrenolytic drugs, as well as on the basis of their dates of publication: 1960-2017. In order to conduct a reliable and complete review of literature, the authors decided to include works from quite an extended period of time. The articles included in the review were published in Polish and English.

Results: The review of articles concerning the treatment of anxiety disorders clearly suggests that propranolol is effective in reducing the frequency of panic attacks and the tendency for avoidance behavior in patients with agoraphobia. Other studies report on potential benefits in terms of early interventional prevention and treating posttraumatic stress disorder with propranolol. However, there is lack of randomized clinical trials concerning the therapeutic effect of other adrenolytic drugs in treating anxiety disorders. Early research works reported that (mainly lipophilic) beta blockers may have a depressogenic effect; however, the latest studies have not confirmed it.

The contemporary research on the therapeutic potential of beta blockers in treating anxiety disorders is insufficient. What seems to be most promising, however, are reports concerning the desirable effects of using adrenolytic drugs in treating posttraumatic stress disorder, which implicates the necessity of conducting further research verifying the validity of their application.

Pharmacotherapy in Generalized Anxiety Disorder: Novel Experimental Medicine Models and Emerging Drug Targets

Many pharmacological and psychological approaches have been found efficacious in patients with generalized anxiety disorder (GAD), but many treatment-seeking patients will not respond and others will relapse despite continuing with interventions that initially had beneficial effects. Other patients will respond but then stop treatment early because of untoward effects such as sexual dysfunction, drowsiness, and weight gain. There is much scope for the development of novel approaches that could have greater overall effectiveness or acceptability than currently available interventions or that have particular effectiveness in specific clinical subgroups. 'Experimental medicine' studies in healthy volunteers model disease states and represent a proof-of-concept approach for the development of novel therapeutic interventions: they determine whether to proceed to pivotal efficacy studies and so can reduce delays in translating innovations into clinical practice. Investigations in healthy volunteers challenged with the inhalation of air 'enriched' with 7.5% carbon dioxide (CO₂) indicate this technique provides a validated and robust experimental medicine model, mirroring the subjective, autonomic, and cognitive features of GAD. The anxiety response during CO₂ challenge probably involves both central noradrenergic neurotransmission and effects on acid-base sensitive receptors and so may stimulate development of novel agents targeted at central chemosensors. Increasing awareness of the potential role of altered cytokine balance in anxiety and the interplay of cytokines with monoaminergic mechanisms may also encourage the investigation of novel agents with modulating effects on immunological profiles. Although seemingly disparate, these two approaches to treatment development may pivot on a shared mechanism in exerting anxiolytic-like effects through pharmacological effects on acid-sensing ion channels.

Biological markers for anxiety disorders, OCD and PTSD: A consensus statement. Part II: Neurochemistry, neurophysiology and neurocognition

OBJECTIVE

Biomarkers are defined as anatomical, biochemical or physiological traits that are specific to certain disorders or syndromes. The objective of this paper is to summarise the current knowledge of biomarkers for anxiety disorders, obsessive-compulsive disorder (OCD) and posttraumatic stress disorder (PTSD).

METHODS

Findings in biomarker research were reviewed by a task force of international experts in the field, consisting of members of the World Federation of Societies for Biological Psychiatry Task Force on Biological Markers and of the European College of Neuropsychopharmacology Anxiety Disorders Research Network.

RESULTS

The present article (Part II) summarises findings on potential biomarkers in neurochemistry (neurotransmitters such as serotonin, norepinephrine, dopamine or GABA, neuropeptides such as cholecystokinin, neurokinins, atrial natriuretic peptide, or oxytocin, the HPA axis, neurotrophic factors such as NGF and BDNF, immunology and CO2 hypersensitivity), neurophysiology (EEG, heart rate variability) and neurocognition. The accompanying paper (Part I) focuses on neuroimaging and genetics.

CONCLUSIONS

Although at present, none of the putative biomarkers is sufficient and specific as a diagnostic tool, an abundance of high quality research has accumulated that should improve our understanding of the neurobiological causes of anxiety disorders, OCD and PTSD.

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.

Evaluating psychological interventions in a novel experimental human model of anxiety

Inhalation of 7.5% carbon dioxide increases anxiety and autonomic arousal and provides a novel experimental model of anxiety with which to evaluate pharmacological and psychological treatments for anxiety. To date several psychotropic drugs including benzodiazepines, SSRIs and SNRIs have been evaluated using the 7.5% CO2 model; however, it has yet to be used to evaluate psychological interventions. We compared the effects of two core psychological components of mindfulness-meditation (open monitoring and focused attention) against general relaxation, on subjective, autonomic and neuropsychological outcomes in the 7.5% CO2 experimental model. 32 healthy screened adults were randomized to complete 10 min of guided open monitoring, focused attention or relaxation, immediately before inhaling 7.5% CO2 for 20 min. During CO2-challenge participants completed an eye-tracking measure of attention control and selective attention. Measures of subjective anxiety, blood pressure and heart rate were taken at baseline and immediately following intervention and CO2-challenge. OM and FA practice reduced subjective feelings of anxiety during 20-min inhalation of 7.5% CO2 compared to relaxation control. OM practice produced a strong anxiolytic effect, whereas the effect of FA was more modest. Anxiolytic OM and FA effects occurred in the absence of group differences in autonomic arousal and eye-movement measures of attention. Our findings are consistent with neuropsychological models of mindfulness-meditation that propose OM and FA activate prefrontal mechanisms that support emotion regulation during periods of anxiety and physiological hyper-arousal. Our findings complement those from pharmacological treatment studies, further supporting the use of CO2 challenge to evaluate future therapeutic interventions for anxiety.

Psychometric properties of the Generalized Anxiety Disorder Inventory in a Canadian sample

The Generalized Anxiety Disorder Inventory is a recently developed self-report measure that assesses symptoms of generalized anxiety disorder. Its psychometric properties have not been investigated further since its original development. The current study investigated its psychometric properties in a Canadian student/community sample. Exploratory principal component analysis replicated the original three-component structure. The total scale and subscales demonstrated excellent internal consistency reliability (α = 0.84-0.94) and correlated strongly with the Penn State Worry Questionnaire (r = 0.41-0.74, all ps <0.001) and Generalized Anxiety Disorder-7 (r = 0.55-0.84, all ps <0.001). However, only the total scale and cognitive subscale (r = 0.48-0.49, all ps <0.05) significantly predicted generalized anxiety disorder diagnosis established by diagnostic interview. The somatic subscale in particular may require revision to improve predictive validity. Revision may also be necessary given changes in required somatic symptoms for generalized anxiety disorder diagnostic criteria in more recent versions of the Diagnostic and Statistical Manual of Mental Disorders (i.e. although major changes occurred from Diagnostic and Statistical Manual of Mental Disorders-III-R to Diagnostic and Statistical Manual of Mental Disorders-IV, changes in Diagnostic and Statistical Manual of Mental Disorders-5 were minimal) and the possibility of changes in the upcoming 11th revision of the International Classification of Diseases.

Anxiolytic effects of vestipitant in a sub-group of healthy volunteers known to be sensitive to CO2 challenge

The pharmacological properties of two NK1 antagonists were studied in comparison with a benzodiazepine during a 7% CO2 challenge in a population of healthy volunteers selected for a high sensitivity to the challenge. In total, 19 healthy subjects, pre-screened for their responsiveness to the 7% CO2 test, took part in the randomised, double-blind, cross-over, incomplete block design study. After receiving treatment or placebo, the volunteers were subjected to three 7% CO2 challenges each for a time of 20 min. The treatment consisted of the administration of the following three active drugs: a single dose of benzodiazepine alprazolam (0.75 mg) and a single dose of the NK1 antagonists vestipitant (GW597599) (15 mg) and vofopitant (GR205171) (25 mg). Anxiety during the challenge was evaluated with Visual Analogue Scale-Anxiety (VAS-A) and with Panic Symptom List (PSL III-R). Respiratory parameters, heart rate and skin conductance were also recorded. Compared with placebo, vestipitant showed a significant reduction (p<0.05) in anxiety assessed on the VAS-A scale (ΔVAS-A%) while alprazolam significantly (p<0.01) attenuated the PSL III-R total score. Vofopitant did not show any anxiolytic effect. In the comparison analysis between placebo and drugs, none of the respiratory and other physiological parameters showed a statistically significant difference.

Evaluation of the effects of venlafaxine and pregabalin on the carbon dioxide inhalation models of Generalised Anxiety Disorder and panic

Previous studies have shown that subjective and objective symptoms of anxiety induced by 7.5% CO(2) inhalation can be attenuated by anxiolytics such as lorazepam and, to a lesser extent, paroxetine. Venlafaxine and pregabalin, two other licensed treatments for Generalised Anxiety Disorder, were used to further investigate the 7.5% and 35% CO(2) models of anxiety in healthy volunteers. Fifty-four participants were randomised to receive either placebo, venlafaxine or pregabalin. Study treatments were dosed incrementally over a three week period, to reach daily doses of 150 mg venlafaxine and 200mg pregabalin by the CO(2) challenge test day. Participants inhaled air 7.5% CO(2) for 20 minutes (single-blind presentation), and a non-blinded single vital capacity of 35% CO(2). Subjective ratings were recorded before and after each inhalation. Both 7.5% and 35% CO(2) inhalations produced the expected effects of increased ratings of symptoms of panic and anxiety, with increased blood pressure and heart rate. No significant treatment effects were found, although there were trends towards a reduction in feeling tense and nervous by both drugs compared with placebo during the 7.5% CO(2) challenge, and a reduction in alertness generally in the venlafaxine group compared with the pregabalin group. In contrast with the clear anxiolytic effects of benzodiazepines reported in several previous CO(2) studies, these findings suggest that the anxiogenic effects of CO(2) challenges are not significantly influenced by these serotonergic and GABAergic anxiolytics. This may be due to a lack of sensitivity of the CO(2) challenges in healthy volunteers to these drug types.

The effect of a clinically effective and non-effective dose of lorazepam on 7.5% CO₂-induced anxiety

Symptoms of anxiety induced by 7.5% CO₂ inhalation can be attenuated by acute administration of GABA(A) receptor anxiolytics such as lorazepam and alprazolam. This study investigated if these effects are dose-related, by comparing a 0.5 mg dose (considered non-clinically effective) and a 2 mg dose of lorazepam (clinically effective) on 7.5% CO₂ inhalation. Eighteen healthy males (mean age 20.6 years, SD 1.29), judged physically and mentally fit, attended three visits, each one week apart, to take each treatment in a randomised double-blind crossover design. Drugs were given 60 min prior to 20 min air inhalation, followed by 20 min 7.5% CO₂ inhalation. The order of gas presentation was single blind. Subjective ratings using visual analogue scales (VAS) and questionnaires were recorded before and after each inhalation. Blood pressure (BP), heart rate (HR), respiration rate (RR) and expired CO₂ were recorded during each inhalation. Inhalation of 7.5% CO₂ significantly raised BP, HR, RR and expired CO₂. Ratings of feeling like leaving the room were significantly lower on 2 mg compared with 0.5 mg and placebo, and dose-dependent trends were seen in scores for VAS fearful, anxious, stressed, tense, and worried. Results may be indicative of dose-dependent effects of lorazepam in a CO₂ model of anxiety.

Oxytocin interference in the effects induced by inhalation of 7.5% CO(2) in healthy volunteers

OBJECTIVE

The objective of this study was to assess the acute effect of intranasally administered oxytocin (OT) on subjective states, cardiovascular, and endocrine parameters in healthy volunteers who inhaled 7.5% CO(2) .

METHODS

Forty-five subjects were allocated into three matched groups of subjects who received 24 international units (IU) of OT, 2 mg of lorazepam (LZP), or placebo (PL). The challenge consisted of medical air inhalation for 20 min, 10 min of rest, and CO(2) 7.5% inhalation for 20 min. Subjective effects were evaluated by self-assessment scales; heart rate, blood pressure, skin conductance, and salivary cortisol were also measured. Assessments were performed at four time points: (i) baseline (-15 min); (ii) post-air inhalation (90 min); (iii) post-CO(2) inhalation (120 min), and (iv) post-test (160 min).

RESULTS

CO(2) inhalation significantly increased the anxiety score in the PL group compared with the post-air measurement but not in the OT or LZP groups. The LZP reduced anxiety after medical air inhalation. Other parameters evaluated were not affected by OT.

CONCLUSION

OT, as well as LZP, prevented CO(2) -induced anxiety, suggesting that this hormone has anxiolytic properties.

Validating the inhalation of 7.5% CO(2) in healthy volunteers as a human experimental medicine: a model of generalized anxiety disorder (GAD)

Anxiety is a complex phenomenon that can represent contextually different experiences to individuals. The experimental modelling in healthy volunteers of clinical anxiety experienced by patients is challenging. Furthermore, defining when and why anxiety (which is adaptive) becomes an anxiety disorder (and hence maladaptive) is the subject of much of the published literature. Observations from animal studies can be helpful in deriving mechanistic models, but gathering evidence from patients and reverse translating this to healthy volunteers and thence back to laboratory models is a more powerful approach and is likely to more closely model the clinical disorder. Thus the development and validation of a robust healthy volunteer model of anxiety may help to bridge the gap between the laboratory and the clinic and provide 'proof of concept' in screening for novel drug treatments. This review considers these concepts and outlines evidence from a validated healthy volunteer model of generalized anxiety disorder (GAD) following the inhalation of 7.5% CO(2).

On the Imposition of Torture, an Extreme Stressor State, to Extract Information From Memory

There is a widespread and popularly-held belief that the imposition of extreme stressor states (torture) is efficacious at facilitating the release of intentionally-withheld information from (human) memory. Here, I explore why this belief is so widespread. I examine the folk model of the brain and behavior that underpins this belief, and show that this folk model is utterly inconsistent with what we currently know about the effects of extreme stressor states on the brain systems that support memory and executive function. Scientific evidence on how repeated and extreme stress and pain affect memory and executive functions (such as planning or forming intentions) suggests that subjecting individuals to such states is unlikely to do anything other than the opposite of what is intended by coercive or “enhanced” interrogation. Coercive interrogations involving imposition of extreme stressor states are unlikely to facilitate the release of veridical information from long-term memory, given our current cognitive neurobiological knowledge. On the contrary, these techniques cause severe, repeated, and prolonged stress, which compromises brain tissue supporting memory and executive function. The fact that the detrimental effects of these techniques on the brain are not visible to the naked eye makes them no less real.

Validating a human model for anxiety using startle potentiated by cue and context: the effects of alprazolam, pregabalin, and diphenhydramine

BACKGROUND

Fear-potentiated startle has been suggested as a translational model for evaluating efficacy of anxiolytic compounds in humans. Several known anxiolytic compounds have been tested as well as several putative anxiolytics. Because results of these studies have been equivocal, the aim of the present study was to examine another pharmacological permutation of the human potentiated startle model by comparing two anxiolytic agents to a non-anxiolytic sedative and placebo.

METHODS

Twenty healthy volunteers participated in a double-blind, placebo-controlled, cross-over study with four sessions in which they received single doses of the anxiolytics alprazolam (1 mg) and pregabalin (200 mg), as well as diphenhydramine (50 mg) as a non-anxiolytic sedative control and placebo. The design included a cued shock condition that presumably evokes fear and an unpredictable shock context condition presumably evoking anxiety.

RESULTS

None of the treatments reliably reduced either fear- or anxiety-potentiated startle. Alprazolam and diphenhydramine reduced overall baseline startle. Alprazolam was found to only affect contextual anxiety in a statistical significant way after two subjects who failed to show a contextual anxiety effect in the placebo condition were excluded from the analysis. Pregabalin did not significantly affect any of the physiological measures.

DISCUSSION

The negative findings from this study are discussed in terms of methodological differences between designs and in variability of startle both between and within study participants.

CONCLUSION

Even though fear-potentiated startle may be used to translate preclinical evidence to human populations, methodological issues still hamper the application of this model to early screening of putative anxiolytic drugs.