Paroxetine: a review

Rebound activation of 5-HT neurons following SSRI discontinuation

Cessation of therapy with a selective serotonin (5-HT) reuptake inhibitor (SSRI) is often associated with an early onset and disabling discontinuation syndrome, the mechanism of which is surprisingly little investigated. Here we determined the effect on 5-HT neurochemistry of discontinuation from the SSRI paroxetine. Paroxetine was administered repeatedly to mice (once daily, 12 days versus saline controls) and then either continued or discontinued for up to 5 days. Whereas brain tissue levels of 5-HT and/or its metabolite 5-HIAA tended to decrease during continuous paroxetine, levels increased above controls after discontinuation, notably in hippocampus. In microdialysis experiments continuous paroxetine elevated hippocampal extracellular 5-HT and this effect fell to saline control levels on discontinuation. However, depolarisation (high potassium)-evoked 5-HT release was reduced by continuous paroxetine but increased above controls post-discontinuation. Extracellular hippocampal 5-HIAA also decreased during continuous paroxetine and increased above controls post-discontinuation. Next, immunohistochemistry experiments found that paroxetine discontinuation increased c-Fos expression in midbrain 5-HT (TPH2 positive) neurons, adding further evidence for a hyperexcitable 5-HT system. The latter effect was recapitulated by 5-HT1A receptor antagonist administration although gene expression analysis could not confirm altered expression of 5-HT1A autoreceptors following paroxetine discontinuation. Finally, in behavioural experiments paroxetine discontinuation increased anxiety-like behaviour, which partially correlated in time with the measures of increased 5-HT function. In summary, this study reports evidence that, across a range of experiments, SSRI discontinuation triggers a rebound activation of 5-HT neurons. This effect is reminiscent of neural changes associated with various psychotropic drug withdrawal states, suggesting a common unifying mechanism.

Effects of selective serotonin reuptake inhibitors on endocrine system (Review)

Selective serotonin reuptake inhibitors (SSRIs) are typically prescribed for treating major depressive disorder (MDD) due to their high efficacy. These drugs function by inhibiting the reuptake of serotonin [also termed 5-hydroxytryptamine (5-HT)], which raises the levels of 5-HT in the synaptic cleft, leading to prolonged activation of postsynaptic 5-HT receptors. Despite the therapeutic benefits of SSRIs, this mechanism of action also disturbs the neuroendocrine response. Hypothalamic-pituitary-adrenal (HPA) axis activity is strongly linked to both MDD and the response to antidepressants, owing to the intricate interplay within the serotonergic system, which regulates feeding, water intake, sexual drive, reproduction and circadian rhythms. The aim of the present review was to provide up-to-date evidence for the proposed effects of SSRIs, such as fluoxetine, citalopram, escitalopram, paroxetine, sertraline and fluvoxamine, on the endocrine system. For this purpose, the literature related to the effects of SSRIs on the endocrine system was searched using the PubMed database. According to the available literature, SSRIs may have an adverse effect on glucose metabolism, sexual function and fertility by dysregulating the function of the HPA axis, pancreas and gonads. Therefore, considering that SSRIs are often prescribed for extended periods, it is crucial to monitor the patient closely with particular attention to the function of the endocrine system.

Obstructive Sleep Apnea and Serotoninergic Signalling Pathway: Pathomechanism and Therapeutic Potential

Obstructive Sleep Apnea (OSA) is a disorder characterized by repeated upper airway collapse during sleep, leading to apneas and/or hypopneas, with associated symptoms like intermittent hypoxia and sleep fragmentation. One of the agents contributing to OSA occurrence and development seems to be serotonin (5-HT). Currently, the research focuses on establishing and interlinking OSA pathogenesis and the severity of the disease on the molecular neurotransmitter omnipresent in the human body-serotonin, its pathway, products, receptors, drugs affecting the levels of serotonin, or genetic predisposition. The 5-HT system is associated with numerous physiological processes such as digestion, circulation, sleep, respiration, and muscle tone-all of which are considered factors promoting and influencing the course of OSA because of correlations with comorbid conditions. Comorbidities include obesity, physiological and behavioral disorders as well as cardiovascular diseases. Additionally, both serotonin imbalance and OSA are connected with psychiatric comorbidities, such as depression, anxiety, or cognitive dysfunction. Pharmacological agents that target 5-HT receptors have shown varying degrees of efficacy in reducing the Apnea-Hypopnea Index and improving OSA symptoms. The potential role of the 5-HT signaling pathway in modulating OSA provides a promising avenue for new therapeutic interventions that could accompany the primary treatment of OSA-continuous positive airway pressure. Thus, this review aims to elucidate the complex role of 5-HT and its regulatory mechanisms in OSA pathophysiology, evaluating its potential as a therapeutic target. We also summarize the relationship between 5-HT signaling and various physiological functions, as well as its correlations with comorbid conditions.

Selective Serotonin Reuptake Inhibitors for the Treatment of Depression in Parkinson's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Although selective serotonin reuptake inhibitors (SSRIs) are usually considered safe to use in patients with Parkinson's disease (PD), there are mixed data about their effectiveness, and only a few investigations have led to a total improvement of depressive symptoms in patients with PD.

OBJECTIVES

We aimed to conduct a comprehensive systematic review and meta-analysis of all studies that investigated the effectiveness of SSRIs in treating depression in the context of PD.

METHODS

From its commencement to June 2024, the databases of MEDLINE via PubMed, Scopus, Embase, and Google Scholar were electronically searched for the relevant papers. All full-text journal articles assessing the effectiveness of SSRIs in treating depression in patients with PD were included. The tool developed by the Cochrane Collaboration was utilized to evaluate the bias risk. Data were analyzed utilizing a pair-wise comparison meta-analysis using the standardized mean difference.

RESULTS

A total of 19 articles and 22 separate interventions were included. We found that SSRI treatment attenuated depression in patients with PD (1.242 standardized mean difference, 95% confidence interval 0.956, 1.529, p < 0.001). The general heterogeneity of the studies was medium (ϰ2 = 72.818, T2 = 0.317, df = 21, I2 = 71.15%, p < 0.001). The funnel plot was reasonably symmetrical. However, three studies were trimmed to the left of the mean. Begg's test (p = 0.080), Egger's test (p = 0.121), and funnel plot showed no significant risk of publication bias. The meta-regression showed that the treatment effect increased as a function of paroxetine treatment duration (slope p = 0.001) but decreased as a function of sertraline treatment duration (slope p = 0.019).

CONCLUSIONS

There are few controlled antidepressant trials on the PD population, even though patients with PD frequently experience depression and use antidepressants. Clinical studies that are larger and better structured are needed in the future to determine if antidepressants are useful for treating patients with PD with depression.

Current Understanding of Compulsive Sexual Behavior Disorder and Co-occurring Conditions: What Clinicians Should Know about Pharmacological Options

Compulsive sexual behavior disorder (CSBD) has recently been recognized as a psychiatric disorder. Pharmacological treatments for CSBD have received little study and thus have limited empirical support. The main objective of the present work is to review existing literature on the efficacy of different drugs on the symptomatology of CSBD, including the subtype of problematic pornography use (PPU). The main pharmacological approaches to treating CSBD have included opioid antagonists (naltrexone and nalmefene), selective serotonin reuptake inhibitors (paroxetine, citalopram, fluoxetine, and sertraline), mood stabilizers (topiramate), tricyclic antidepressants (clomipramine), serotonin antagonist and reuptake inhibitors (nefazodone), and N-acetylcysteine. Since people with CSBD may experience different co-occurring disorders, these should be considered when choosing the best pharmacological treatment. Pharmacological therapy for CSBD/PPU has been suggested as an adjunct to psychological therapies, which, for the moment, have the most empirical evidence. However, to evaluate the efficacy of most of the drugs presented in this narrative review, data to date have only been available from case studies. Thus, empirical support is scant and generalizability of results is limited, highlighting the need for more research in this area.

Inhibition of TNBC Cell Growth by Paroxetine: Induction of Apoptosis and Blockage of Autophagy Flux

The strategy of drug repurposing has gained traction in the field of cancer therapy as a means of discovering novel therapeutic uses for established pharmaceuticals. Paroxetine (PX), a selective serotonin reuptake inhibitor typically utilized in the treatment of depression, has demonstrated promise as an agent for combating cancer. Nevertheless, the specific functions and mechanisms by which PX operates in the context of triple-negative breast cancer (TNBC) remain ambiguous. This study aimed to examine the impact of PX on TNBC cells in vitro as both a standalone treatment and in conjunction with other pharmaceutical agents. Cell viability was measured using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, apoptosis was assessed through flow cytometry, and the effects on signaling pathways were analyzed using RNA sequencing and Western blot techniques. Furthermore, a subcutaneous tumor model was utilized to assess the in vivo efficacy of combination therapy on tumor growth. The results of our study suggest that PX may activate the Ca2+-dependent mitochondria-mediated intrinsic apoptosis pathway in TNBC by potentially influencing the PI3K/AKT/mTOR pathway as well as by inducing cytoprotective autophagy. Additionally, the combination of PX and chemotherapeutic agents demonstrated moderate inhibitory effects on 4T1 tumor growth in an in vivo model. These findings indicate that PX may exert its effects on TNBC through modulation of critical molecular pathways, offering important implications for improving chemosensitivity and identifying potential therapeutic combinations for clinical use.

Molecular mechanisms of cholinergic neurotransmission in visceral smooth muscles with a focus on receptor-operated TRPC4 channel and impairment of gastrointestinal motility by general anaesthetics and anxiolytics

Acetylcholine is the primary excitatory neurotransmitter in visceral smooth muscles, wherein it binds to and activates two muscarinic receptors subtypes, M2 and M3, thus causing smooth muscle excitation and contraction. The first part of this review focuses on the types of cells involved in cholinergic neurotransmission and on the molecular mechanisms underlying acetylcholine-induced membrane depolarisation, which is the central event of excitation-contraction coupling causing Ca2+ entry via L-type Ca2+ channels and smooth muscle contraction. Studies of the muscarinic cation current in intestinal myocytes (mICAT) revealed its main molecular counterpart, receptor-operated TRPC4 channel, which is activated in synergy by both M2 and M3 receptors. M3 receptors activation is of permissive nature, while activation of M2 receptors via Gi/o proteins that are coupled to them plays a direct role in TRPC4 opening. Our understanding of signalling pathways underlying mICAT generation has vastly expanded in recent years through studies of TRPC4 gating in native cells and its regulation in heterologous cells. Recent studies using muscarinic receptor knockout have established that at low agonist concentration activation of both M2 receptor and the M2/M3 receptor complex elicits smooth muscle contraction, while at high agonist concentration M3 receptor function becomes dominant. Based on this knowledge, in the second part of this review we discuss the cellular and molecular mechanisms underlying the numerous anticholinergic effects on neuroactive drugs, in particular general anaesthetics and anxiolytics, which can significantly impair gastrointestinal motility. This article is part of the Special Issue on "Ukrainian Neuroscience".

Mechanisms of SSRI Therapy and Discontinuation

SSRIs are one of the most widely used drug therapies in primary care and psychiatry, and central to the management of the most common mental health problems in today's society. Despite this, SSRIs suffer from a slow onset of therapeutic effect and relatively poor efficacy as well as adverse effects, with recent concerns being focused on a disabling SSRI discontinuation syndrome. The mechanism underpinning their therapeutic effect has long shifted away from thinking that SSRIs act simply by increasing 5-HT in the synapse. Rather, a current popular view is that increased 5-HT is just the beginning of a series of complex downstream signalling events, which trigger changes in neural plasticity at the functional and structural level. These changes in plasticity are then thought to interact with neuropsychological processes to enhance re-learning of emotional experiences that ultimately brings about changes in mood. This compelling view of SSRI action is underpinning attempts to understand fast-acting antidepressants, such as ketamine and psychedelic drugs, and aid the development of future therapies. An important gap in the theory is evidence that changes in plasticity are causally linked to relevant behavioural effects. Also, predictions that the SSRI-induced neural plasticity might have applicability in other areas of medicine have not yet been borne out. In contrast to the sophisticated view of the antidepressant action of SSRIs, the mechanism underpinning SSRI discontinuation is little explored. Nevertheless, evidence of rebound increases in 5-HT neuron excitability immediately on cessation of SSRI treatment provide a starting point for future investigation. Indeed, this evidence allows formulation of a mechanistic explanation of SSRI discontinuation which draws on parallels with the withdrawal states of other psychotropic drugs.

Are early and young life stages of fish affected by paroxetine? A case study with Danio rerio

Paroxetine (PAR) is a selective serotonin reuptake inhibitor (SSRI) antidepressant increasingly detected in surface waters worldwide. Its environmental presence raises concerns about the potential detrimental effects on non-target organisms. Thus, this study aimed to increase knowledge on PAR's potential environmental impacts, assessing the effects of commercial formulation (PAR-c) and active ingredient (PAR-a) on fish. Therefore, the short-term exposure effects of PAR-c and PAR-a were assessed on zebrafish (Danio rerio) embryos/larvae to determine the most toxic formulation [through median lethal (LC50) and effective concentrations (EC50)]. PAR-c and PAR-a induced morphological abnormalities (scoliosis) in a dose-dependent manner from 96 hours post-fertilization onwards, suggesting the involvement of a fully functional biotransformation system. As PAR-c exhibited higher toxicity, it was selected to be tested in the subsequent stage (juvenile stage), which was more sensitive (lower LC50). PAR-c significantly decreased fish swimming activity and disrupted fish stress response. Overall, the results highlight the ability of PAR-c to adversely affect fish swimming performance, an effect that persisted even after exposure ceases (21-day depuration), suggesting that PAR-c may impair individual fitness.

Exploring Environmental Settings to Improve the Printability of Paroxetine-Loaded Filaments by Fused Deposition Modelling

The successful integration of hot-melt extrusion (HME) and fused deposition modelling (FDM) depends on a better understanding of the impact of environmental conditions on the printability of formulations, since they significantly affect the properties of the raw materials, whose control is crucial to enable three-dimensional printing (3DP). Hence, the objective of this work was to investigate the correlation between the environmental settings and the properties of paroxetine (PRX)-loaded filaments, previously produced by HME, which affect printability by FDM. The influence of different drying methods of the physical mixtures (PMs) and HME-filaments (FILs) on the quality and printability of these products was also assessed. The printability of FILs was evaluated in terms of the water content, and the mechanical and thermal properties of the products. Stability studies and physicochemical, thermal, and in vitro dissolution tests were carried out on the 3D-printed tablets. Stability studies demonstrated the high ductility of the PRX loaded FILs, especially under high humidity conditions. Under low humidity storage conditions (11% RH), the FILs became stiffer and were successfully used to feed the FDM printer. Water removal was slow when carried out passively in a controlled atmosphere (desiccator) or accelerated by using active drying methods (heat or microwave). Pre-drying of the PRX/excipients and/or PMs did not show any positive effect on the printability of the FIL. On the contrary, dry heat and, preferably, microwave mediated drying processes were shown to reduce the holding time required for successful FDM printing, enabling on-demand production at the point of care.

Psychological status of patients with functional anorectal pain and treatment efficacy of paroxetine in alleviating the symptoms: a retrospective study

The aim of this study was to investigate the clinical characteristics, psychological status, sleep quality, and quality of life of patients with functional anorectal pain (FAP). The study also assessed the treatment efficacy of paroxetine in alleviating FAP symptoms. A retrospective comparative study of forty-three patients with FAP who were first treated with an anal plug compound glycolate suppository versus paroxetine combined with anal plug compound glycolate suppository between November 2021 and August 2022. Pain, quality of life, depression, anxiety and sleep quality were assessed before and after treatment by the Chinese version of the Short-Form McGill Pain Questionnaire-2 (SF-MPQ-2), Health-related quality of life scale (The 12-Item Short-Form Health Survey, SF-12), 17-item Hamilton Depression Rating Scale (HDRS), 14-item Hamilton Anxiety Scale (HAMA), and Pittsburgh Sleep Quality Index (PSQI). A total of 46.5% of patients with FAP were found to have anxiety symptoms (HAMA ≥ 7), 37.2% of patients with FAP were found to have depressive symptoms (HDRS ≥ 8). A total of 32.6% of patients with FAP had sleep disorders (PSQI > 10). Within 1 week after drug withdrawal, the short-term efficacy rate of oral paroxetine was 95.5%. After treatment, the symptom pain score (VAS) and sleep score were lower than those before treatment (P < 0.01). In the areas of vitality (VT), Social Functioning (SF), and Mental Health (MH), the difference between the pre-treatment and 8 weeks posttreatment scores of the study group and the control group was statistically significant (P < 0.05). FAP patients have obvious symptoms of anxiety and depression, and the incidence of sleep disturbance is prevalent. Paroxetine, a typical serotonin reuptake inhibitor (SSRI), was able to alleviate depression, anxiety, and pain symptoms in FAP, which might have clinical application prospects.

A Comprehensive Review of the Generalized Anxiety Disorder

Excessive, uncontrollable, and usually unjustified worry about certain things is a sign of the mental and behavioral disease known as generalized anxiety disorder (GAD). Genetic research suggests that numerous genes are likely implicated in the development of GAD, even if much is yet unclear about this. As a result, if someone in a family has GAD, there is a high likelihood that someone else will also suffer from the illness, as well as another anxiety disorder. Individuals with GAD are frequently overly bothered about workaday affairs like health, assets, demise, family, accord issues, or effort challenges. Worry frequently interferes with daily functioning. Excessive concern, restlessness, difficulty sleeping, tiredness, irritability, sweating, and trembling are a few symptoms that may be present. For a formal diagnosis of GAD, symptoms must be persistent for at least six months and consistent. Conversion in the amygdala's utilitarian congruence and how it processes fear and anxiety have been linked to generalized anxiety disorder. Neurotransmitters, and particularly the gamma-aminobutyric acid (GABA) variant, have long been known to cause GAD through dysregulating amygdala activity in the brain. Anxiety, concern, or physical symptoms must significantly hinder social, academic, or occupational functioning in order to qualify for a GAD diagnosis. The Diagnostic and Statistical Manual of Mental Disorders-V (DSM-V) provides explicit ethos to aid doctors in identifying this disorder. Psychological therapy based on cognitive behavioral therapy (CBT) principles is effective in reducing anxiety symptoms for short-term treatment of GAD. In this, the patient's thinking ability and methods are focused. The main principle behind CBT is that your thought patterns affect your feelings, which in turn can affect your behavior. Drugs like antidepressants, buspirone, benzodiazepines, and can all be worn to goody GAD. Outside of therapy, patients with anxiety can learn to manage it by practicing relaxation methods, reframing unfavorable ideas, and adopting stress-relieving adjustments. Being socially active and setting aside time for proper self-care are crucial components of managing generalized anxiety disorder.

Role of Selective Serotonin Reuptake Inhibitors in the Treatment of Hypochondriasis: A Systematic Review

Hypochondriasis is a condition characterized by an unrealistic fear of having a serious medical illness resulting in health anxiety. Currently, no evidence-based pharmacological treatment options are available for the treatment of hypochondriasis. Since selective serotonin reuptake inhibitors (SSRIs) are the first-line treatment option for anxiety disorders, they may be useful for relieving hypochondriasis symptoms. Moreover, off-label use of SSRIs in these cases is highly prevalent in clinical practice. Thus, in this study, we aimed to review the available literature to assess the role of SSRIs in the treatment of hypochondriacal symptoms. A systematic search was conducted in PubMed, Scopus, ScienceDirect, Embase, and Cochrane Database of Systematic Reviews from the date of inception to December 2022. We included only randomized clinical trials (RCTs) investigating the effect of SSRIs in the treatment of hypochondriacal symptoms. Non-RCTs, observation studies, and animal studies were excluded. The Risk of Bias 2 tool was used to assess the quality of included studies. Out of 2264 articles, six RCTs met our inclusion criteria. Studies have been conducted using different SSRIs in the treatment of primary hypochondriasis and hypochondriacal symptoms associated with other psychiatric disorders. All the studies have found that the use of SSRIs has some beneficial role in improving hypochondriacal symptoms. This suggests that SSRIs may be one of the promising pharmacological interventions in the treatment of hypochondriasis.

A new approach methodology using kinetically-derived maximum dose levels in risk assessment - A case study with afidopyropen

We present a case study for afidopyropen (AF; insecticide) to characterize chronic dietary human health risk using a Risk 21-based approach. Our objective is to use a well-tested pesticidal active ingredient (AF) to show how a new approach methodology (NAM), using the kinetically-derived maximum dose (KMD) and with far less animal testing, can reliably identify a health-protective point of departure (PoD) for chronic dietary human health risk assessments (HHRA). Chronic dietary HHRA involves evaluation of both hazard and exposure information to characterize risk. Although both are important, emphasis has been placed on a checklist of required toxicological studies for hazard characterization, with human exposure information only considered after evaluation of hazard data. Most required studies are not used to define the human endpoint for HHRA. The information presented demonstrates a NAM that uses the KMD determined by saturation of a metabolic pathway, which can be used as an alternative POD. In these cases, the full toxicological database may not need to be generated. Demonstration that the compound is not genotoxic and that the KMD is protective of adverse effects in 90-day oral rat and reproductive/developmental studies is sufficient to support the use of the KMD as an alternative POD.

Lycium barbarum (Wolfberry) glycopeptide prevents stress-induced anxiety disorders by regulating oxidative stress and ferroptosis in the medial prefrontal cortex

BACKGROUND

Lycium barbarum (Wolfberry) extract has been shown to be effective in neuroprotection against aging or neural injury. Knowledge of its potential roles and biological mechanisms in relieving mental disorders, however, remains limited.

PURPOSE

To investigate the potency of Lycium barbarum glycopeptide (LbGp) in alleviating anxiety disorders and the related biological mechanisms.

METHODS

LbGp was administrated to mice subjected to 14 days of chronic restrain stress (CRS) via the intragastric route. The anxiolytic effect was evaluated by a battery of behavioral assays. The morphology of neurons and glial cells was evaluated, and cortical neuronal calcium transients were recorded in vivo. The molecular mechanism of LbGp was also investigated.

RESULTS

LbGp effectively relieved anxiety-like and depressive behaviors under CRS. Mechanistic studies further showed that LbGp treatment relieved oxidative stress and lipid peroxidation in the medial prefrontal cortex (mPFC). In particular, the ferroptosis pathway was inhibited by LbGp, revealing a previously unrecognized mechanism of the anxiolytic role of wolfberry extract.

CONCLUSION

In summary, our results supported the future development of LbGp to prevent or ameliorate stress-induced anxiety disorders. Our work provides a promising strategy for early intervention for pateitents with mental disorders by applying natural plant extracts.

Antidepressant pharmaceuticals in aquatic systems, individual-level ecotoxicological effects: growth, survival and behavior

The growing consumption of antidepressant pharmaceuticals has resulted in their widespread occurrence in the environment, particularly in waterways with a typical concentration range from ng L^-1 to μg L^-1. An increasing number of studies have confirmed the ecotoxic potency of antidepressants, not only at high concentrations but also at environmentally relevant levels. The present review covers literature from the last decade on the individual-level ecotoxicological effects of the most commonly used antidepressants, including their impact on behavior, growth, and survival. We focus on the relationship between antidepressants physico-chemical properties and dynamics in the environment. Furthermore, we discuss the advantages of considering behavioral changes as sensitive endpoints in ecotoxicology, as well as some current methodological shortcomings in the field, including low standardization, reproducibility and context-dependency.

Antibacterial activity of paroxetine against Staphylococcus aureus and possible mechanisms of action

Aim: To evaluate the antibacterial activity of paroxetine alone and associated with oxacillin against isolates of methicillin-sensitive and -resistant Staphylococcus aureus. Materials & methods: The broth microdilution and checkerboard techniques were used, with investigation of possible mechanisms of action through flow cytometry, fluorescence microscopy and molecular docking, in addition to scanning electron microscopy for morphological analysis. Results: Paroxetine showed a MIC of 64 μg/ml and bactericidal activity, mostly additive interactions in combination with oxacillin, evidence of action on genetic material and membrane, morphological changes in microbial cells and influence on virulence factors. Conclusion: Paroxetine has antibacterial potential from the perspective of drug repositioning.

P2X receptors: Insights from the study of the domestic dog

Fifty years ago, the late Geoffrey Burnstock described the concept of purinergic nerves and transmission bringing into existence the broader concepts of purinergic signaling including P2X receptors. These receptors are trimeric ligand-gated cation channels activated by extracellular adenosine 5'-triphosphate (ATP). P2X receptors have important roles in health and disease and continue to gain interest as potential therapeutic targets in inflammatory, neurological, cardiovascular and many other disorders including cancer. Current understanding of P2X receptors has largely arisen from the study of these receptors in humans and rodents, but additional insights have been obtained from the study of P2X receptors in the domestic dog, Canis familiaris. This review article will briefly introduce purinergic signaling and P2X receptors, before detailing the pharmacological profiles of the two recombinant canine P2X receptors studied to date, P2X7 and P2X4. The article will then describe the current state of knowledge concerning the distribution and function of the P2X receptor family in dogs. The article will also discuss the characterization of single nucleotide polymorphisms in the canine P2RX7 gene, and contrast this variation to the canine P2RX4 gene, which is largely conserved between dogs. Finally, this article will outline published examples of the use of dogs to study the pharmacokinetics of P2X7 and P2X3 antagonists, and how they have contributed to the preclinical testing of antagonists to human P2X7, CE-224,535, and human P2X3, Gefapixant (AF-219, MK-7264) and Eliapixant (BAY, 1817080), with Gefapixant gaining recent approval for use in the treatment of refractory chronic cough in humans. This article is part of the Special Issue on 'Purinergic Signaling: 50 years'.

Elucidating the interaction of antidepressant drug paroxetine with ct-dsDNA: A comparative study by electrochemical, spectroscopic, and molecular docking approaches

This study is designed to investigate the interaction of phenylpiperidine derivative drug paroxetine, which is an effective serotonin reuptake inhibitor and biomolecules through electrochemical, fluorescence spectroscopy, and molecular docking methods. The interaction between paroxetine and biomolecules was investigated by differential pulse voltammetry according to the decrease in deoxyguanosine anodic oxidation signal of double-stranded calf thymus DNA. Fluorescence spectroscopy studies were performed by titrating paroxetine against double-stranded calf thymus DNA solution at four different temperatures. The fluorescent results showed that paroxetine had a great affinity to bind with double-stranded calf thymus DNA. Interaction studies demonstrate that paroxetine binds to double-stranded calf thymus DNA via intercalation binding mode, and the binding constant values ​​were calculated as 7.24 × 10⁴ M^-1 and 1.52 × 10⁴ M^-1 at 25 °C, based on voltammetric and spectroscopic results, respectively. Moreover, with the aim of elucidating the interaction mechanism between paroxetine and double-stranded calf thymus DNA, electrochemical and fluorescence spectroscopy studies along with molecular docking analysis were made.

The effects of α-lactalbumin supplementation and handgrip contraction on soleus motoneuron excitability

INTRODUCTION

We tested two strategies that hypothetically increase serotonin availability (α-lactalbumin consumption and a remote submaximal handgrip contraction) on estimates of persistent inward currents (PICs) amplitude of soleus muscle in healthy participants.

METHODS

With a randomised, double-blind, and cross-over design, 13 healthy participants performed triangular-shaped ramp contractions with their plantar flexors (20% of maximal torque), followed by a 30-s handgrip sustained contraction (40% of maximal force) and consecutive repeated triangular-shaped contractions. This was performed before and after the consumption of either 40 g of α-lactalbumin, an isonitrogenous beverage (Zein) or an isocaloric beverage (Corn-starch). Soleus motor units discharge rates were analysed from high-density surface electromyography signals. PICs were estimated by calculating the delta frequency (ΔF) of motor unit train spikes using the paired motor unit technique.

RESULTS

ΔF (0.19 pps; p = 0.001; d = 0.30) and peak discharge rate (0.20 pps; p < 0.001; d = 0.37) increased after the handgrip contraction, irrespective of the consumed supplement. No effects of α-lactalbumin were observed.

CONCLUSIONS

Our results indicate that 40 g of α-lactalbumin was unable to modify intrinsic motoneuron excitability. However, performing a submaximal handgrip contraction before the plantar flexion triangular contraction was capable of increasing ΔF and discharge rates on soleus motor units. These findings highlight the diffused effects of serotonergic input, its effects on motoneuron discharge behaviour, and suggest a cross-effector effect within human motoneurons.

The Effect of Irisin on Thyroid Hormone Levels in Chronic Paroxetine-Treated Rats

It is known that serotonin reuptake inhibitors (SSRIs), which are widely used in mood disorders, affect the hypothalamic-pituitary-thyroid axis activity. In this study, we investigated the effect of paroxetine, an SSRI, on thyroid hormone levels in rats. We also examined the role of irisin, a newly discovered potential regulatory hormone for metabolism, on paroxetine-induced changes. A total of 64 Sprague-Dawley female and male rats were randomly divided into four subgroups for each gender and treated as follows: sham-operated control (vehicle), paroxetine (treated with 20 mg/kg paroxetine by oral gavage), irisin (100 ng/kg/day for 28 days with mini-osmotic pumps), and paroxetine + irisin group (n = 8). Serum fasting free triiodothyronine (fT3) and free thyroxine (fT4) levels were measured by automated chemiluminescence method. Serum thyroid-stimulating hormone (TSH) level was determined with enzyme-linked immunosorbent analysis (ELISA). Compared to the sham control group (p < 0.05), the significantly reduced fT4 and TSH serum levels in paroxetine-treated male animals were markedly increased by subcutaneous irisin perfusion. fT3 levels significantly increased in both irisin (4.35 ± 0.17 pq/mL) and paroxetine + irisin groups (4.51 ± 0.19 pq/mL) compared to sham control (3.60 ± 0.23 pq/mL) and paroxetine groups (3.57 ± 0.12 pq/mL) (p < 0.05). It was observed that serum fT3, fT4, and TSH levels decreased in female animals receiving paroxetine compared to the sham control group. Subcutaneous administration of irisin increased these hormone levels. However, these changes were not statistically significant. These results suggested that irisin may play a role in the mechanism underlying the beneficial effects of exercise in preventing SSRI-related side effects by increasing thyroid hormone levels, which were decreased by paroxetine.

Targeted inhibition of the GRK2/HIF-1α pathway is an effective strategy to alleviate synovial hypoxia and inflammation

G-protein coupled receptor (GPCR) kinases (GRKs) and hypoxia-inducible factor-1α (HIF-1α) play key roles in rheumatoid arthritis (RA). Several studies have demonstrated that HIF-1α expression is positively regulated by GRK2, suggesting its posttranscriptional effects on HIF-1α. In this study, we review the role of HIF-1α and GRK2 in RA pathophysiology, focusing on their proinflammatory roles in immune cells and fibroblast-like synoviocytes (FLS).We then introduce several drugs that inhibit GRK2 and HIF-1α, and briefly outline their molecular mechanisms. We conclude by presenting gaps in knowledge and our prospects for the pharmacological potential of targeting these proteins and the relevant downstream signaling pathways.Future research is warranted and paramount for untangling these novel and promising roles for GRK2 and HIF-1α in RA.

Recent Development of Nano-Carbon Material in Pharmaceutical Application: A Review

Carbon nanomaterials have attracted researchers in pharmaceutical applications due to their outstanding properties and flexible dimensional structures. Carbon nanomaterials (CNMs) have electrical properties, high thermal surface area, and high cellular internalization, making them suitable for drug and gene delivery, antioxidants, bioimaging, biosensing, and tissue engineering applications. There are various types of carbon nanomaterials including graphene, carbon nanotubes, fullerenes, nanodiamond, quantum dots and many more that have interesting applications in the future. The functionalization of the carbon nanomaterial surface could modify its chemical and physical properties, as well as improve drug loading capacity, biocompatibility, suppress immune response and have the ability to direct drug delivery to the targeted site. Carbon nanomaterials could also be fabricated into composites with proteins and drugs to reduce toxicity and increase effectiveness in the pharmaceutical field. Thus, carbon nanomaterials are very effective for applications in pharmaceutical or biomedical systems. This review will demonstrate the extraordinary properties of nanocarbon materials that can be used in pharmaceutical applications.

Pharmacokinetics of immediate and sustained-release formulations of paroxetine: Population pharmacokinetic approach to guide paroxetine personalized therapy in chinese psychotic patients

Paroxetine is one of the most potent selective serotonin reuptake inhibitors (SSRIs) approved for treating depression, panic disorder, and obsessive-compulsive disorder. There is evidence linking genetic polymorphisms and nonlinear metabolism to the Paroxetine’s pharmacokinetic (PK) variability. The purpose of the present study was to develop a population PK (PPK) model of paroxetine in Chinese patients, which was used to define the paroxetine’s PK parameters and quantify the effect of clinical and baseline demographic factors on these PK characteristics. The study included 184 inpatients with psychosis (103 females and 81 males), with a total of 372 serum concentrations of paroxetine for PPK analyses. The total daily dosage ranged from 20 to 75 mg. One compartment model could fit the PKs characterize of paroxetine. Covariate analysis revealed that dose, formulation, and sex had a significant effect on the PK parameters of paroxetine; however, there was no evident genetic influence of CYP2D6 enzymes on paroxetine concentrations in Chinese patients. The study determined that the population’s apparent distribution volume (V/F) and apparent clearance (CL/F), respectively, were 8850 and 21.2 L/h. The CL/F decreased 1-2-fold for each 10 mg dose increase, whereas the different formulations caused a decrease in V/F of 66.6%. Sex was found to affect bioavailability (F), which decreased F by 47.5%. Females had higher F values than males. This PPK model described data from patients with psychosis who received paroxetine immediate-release tablets (IR-T) and/or sustained-release tablets (SR-T). Paroxetine trough concentrations and relative bioavailability were different between formulations and sex. The altered serum concentrations of paroxetine resulting from individual variants and additive effects need to be considered, to optimize the dosage regimen for individual patients.

Enhanced availability of serotonin limits muscle activation during high-intensity, but not low-intensity, fatiguing contractions

Serotonin (5-HT) modulates motoneuron excitability during muscle contractions, where the release of 5-HT in the central nervous system (CNS) is linked to the intensity of physical activity. Although there is evidence that enhanced availability of 5-HT can exacerbate fatigue, these effects on the development of fatigue during different contraction intensities are largely unknown. The purpose of this study was to investigate how enhanced 5-HT availability affects voluntary muscle activation and corticospinal excitability during fatigue-inducing contractions. Two experiments were performed. In the first experiment (n = 11), twelve isometric elbow flexions at 20% maximal voluntary contractions (MVC) were performed for 2-min each with 40-s rest periods. In the second experiment (n = 14), twelve maximal isometric elbow flexions were held for 10-s each with 40-s rest periods. In both experiments, the selective serotonin reuptake inhibitor (20 mg paroxetine), or a placebo, was administered in a two-way crossover-design. Muscle responses to transcranial magnetic stimulation (TMS) of the motor cortex (both experiments 1 and 2), as well as motor point stimulation of the elbow flexors (experiment 2) were assessed. Paroxetine reduced both motor cortical (p = 0.018) and motor point voluntary activation (p = 0.036) during the maximal contraction protocol. Paroxetine also reduced exercise-induced lengthening of the TMS silent period during the submaximal (p = 0.037) and maximal (p = 0.002) contraction protocols. Activation of inhibitory 5-HT_1A receptors on motoneurons likely exacerbated exercise-induced reductions in voluntarily drive to the elbow flexors. However, 5-HT modulation of motor activity also appeared at the supraspinal level.

Phenols in Pharmaceuticals: Analysis of a Recurring Motif

Phenols and phenolic ethers are significant scaffolds recurring both in nature and among approved small-molecule pharmaceuticals. This compendium presents the first comprehensive compilation and analysis of the structures of U.S. FDA-approved molecules containing phenol or phenolic ether fragments. This dataset comprises 371 structures, which are strongly represented by natural products. A total of 55 of the compounds described here are on the World Health Organization's list of essential medicines. Structural analysis reveals significant differences in the physicochemical properties imparted by phenols versus phenol ethers, each having benefits and drawbacks for drug developability. Despite trends over the past decade to increase the fraction of sp³ centers in drug leads, thereby "escaping flatland", phenols and phenolic ethers are represented in 62% of small-molecule drugs approved in 2020, suggesting that this aromatic moiety holds a special place in drugs and natural products.

Delayed ejaculation in men with depressive disorders

Delayed ejaculation belongs to the group of sexual disorders in men. The causes of delayed ejaculation or anejaculation are not exactly known. It is assumed that it can be caused by psychogenic or organic influences or their combinations. One of the causes of delayed ejaculation may be elevated prolactin levels, which may be increased by psychosocial stress, pituitary disorders or also treatment with selective serotonin reuptake inhibitors in the treatment of depression. We tested a selected group of 50 men who were diagnosed with a depressive disorder and whose antidepressant treatment lasted for at least 24 weeks. These patients reported long-term delayed ejaculation or, in some cases, anejaculation as comorbidity. The results showed significant Spearman's correlation between elevated prolactin levels and intravaginal ejaculation latency values (R = 0.45), as well as between Beck's Depression-II inventory and intravaginal ejaculation latency and latency values (R = 0.48).

Physiological tremor is suppressed and force steadiness is enhanced with increased availability of serotonin regardless of muscle fatigue

Although there is evidence that 5-HT acts as an excitatory neuromodulator to enhance maximal force generation, it is largely unknown how 5-HT activity influences the ability to sustain a constant force during steady-state contractions. A total of 22 healthy individuals participated in the study, where elbow flexion force was assessed during brief isometric contractions at 10% maximal voluntary contraction (MVC), 60% MVC, MVC, and during a sustained MVC. The selective serotonin reuptake inhibitor, paroxetine, suppressed physiological tremor and increased force steadiness when performing the isometric contractions. In particular, a main effect of drug was detected for peak power of force within the 8-12 Hz range (P = 0.004) and the coefficient of variation (CV) of force (P < 0.001). A second experiment was performed where intermittent isometric elbow flexions (20% MVC sustained for 2 min) were repeatedly performed so that serotonergic effects on physiological tremor and force steadiness could be assessed during the development of fatigue. Main effects of drug were once again detected for peak power of force in the 8-12 Hz range (P = 0.002) and CV of force (P = 0.003), where paroxetine suppressed physiological tremor and increased force steadiness when the elbow flexors were fatigued. The findings of this study suggest that enhanced availability of 5-HT in humans has a profound influence of maintaining constant force during steady-state contractions. The action of 5-HT appears to suppress fluctuations in force regardless of the fatigue state of the muscle.NEW & NOTEWORTHY Converging lines of research indicate that enhanced serotonin availability increases maximal force generation. However, it is largely unknown how serotonin influences the ability to sustain a constant force. We performed two experiments to assess physiological tremor and force steadiness in unfatigued and fatigued muscle when serotonin availability was enhanced in the central nervous system. Enhanced availability of serotonin reduced physiological tremor amplitude and improved steadiness regardless of muscle fatigue.

An Iron-Mesoionic Carbene Complex for Catalytic Intramolecular C-H Amination Utilizing Organic Azides

The synthesis of N-heterocycles is of paramount importance for the pharmaceutical industry. They are often synthesized through atom economic and environmentally unfriendly methods, generating significant waste. A less explored, but greener, alternative is the synthesis through the direct intramolecular C-H amination utilizing organic azides. Few examples exist by using this method, but many are limited due to the required use of stoichiometric amounts of Boc₂O. Herein, we report a homoleptic C,O-chelating mesoionic carbene-iron complex, which is the first iron-based complex that does not require the addition of any protecting groups for this transformation and that is active also in strong donor solvents such as THF or even DMSO. The achieved turnover number is an order of magnitude higher than any other reported catalytic system. A variety of C-H bonds were activated, including benzylic, primary, secondary, and tertiary. By following the reaction over time, we determined the presence of an initiation period. Kinetic studies showed a first-order dependence on substrate concentration and half-order dependence on catalyst concentration. Intermolecular competition reactions with deuterated substrate showed no KIE, while separate reactions with deuterium-labeled substrate resulted in a KIE of 2.0. Moreover, utilizing deuterated substrate significantly decreased the initiation period of the catalysis. Preliminary mechanistic studies suggest a unique mechanism involving a dimeric iron species as the catalyst resting state.

Paroxetine mitigates cardiac remodelling by doxorubicin and increases survival

Doxorubicin (DOX) is an effective anticancer drug. However, its use is hampered by the development of very mortal cardiomyopathy. Here, we investigate whether the co-administration of the antidepressant paroxetine (P), known to exert beneficial cardiovascular effects, would provide effective cardioprotection. Experiments were performed in male Wistar rats randomly assigned to control group (0.5 mL/kg 0.9% NaCl, i.v., n = 7), DOX group (DOX 5 mg /kg i.v., n = 23) and DOX+P group (DOX 5 mg/kg, i.v. plus P 10 mg/kg p.o. daily, beginning five days before DOX administration and during the follow-up period, n = 11). Rats' body weight and echocardiography parameters were monitored before and after drug/vehicle administration. Cardiac histology was performed post-mortem, as well as beta1-adrenergic receptor (β₁-AR), beta2-adrenergic receptor (β₂-AR), G protein-coupled receptor kinases type 2 (GRK2), type 3 (GRK3), beta-arrestin 1, and beta-arrestin 2 gene expression using RT-qPCR. DOX-treated rats exhibited bad general condition, adynamia, loss of body weight, and low survival. Echocardiography revealed two phenotypes: cardiomyopathy with left ventricular (LV) hypertrophy (DOX-HCM) and cardiomyopathy with LV dilation (DOX-DCM). In DOX-HCM rats only, there was an increased GRK2 and GRK3 gene expression and synthesis. DOX+P co-treated rats exhibited good general condition, normal spontaneous behaviour, gained weight over time, had increased survival, and preserved LV morphology and contractility. In these rats, gene expression and synthesis of GRK2 and GRK3 were decreased, while β₁-AR and β₂-AR were increased. Present results show for the first time that P effectively reduces DOX-induced cardiotoxicity and enhances survival.

Chronic intranasal oxytocin reverses stress-induced social avoidance in female prairie voles

Social anxiety disorder (SAD) is a prevalent mental illness in both men and women, but current treatment approaches with selective serotonin reuptake inhibitors (SSRI) have limited success. The neuropeptide oxytocin (OXT) has become a therapeutic target due to its prosocial and anxiolytic effects. Nevertheless, no research has focused on the impact of chronic OXT treatment in animal models of SAD. Social defeat stress is an animal model of social conflict that reliably induces a social avoidance phenotype, reflecting symptoms observed in individuals suffering from SAD. Here, we used the socially monogamous prairie vole, which exhibits aggressive behavior in both sexes, to examine the effects of OXT and SSRI treatment following social defeat stress in males and females. Defeated voles became avoidant in unfamiliar social situations as early as one day after defeat experience, and this phenotype persisted for at least eight weeks. OXT receptor (OXTR) binding in mesocorticolimbic and paralimbic regions was reduced in defeated females during the eight-week recovery period. In males, serotonin 1A receptor binding was decreased in the basolateral amygdala and dorsal raphe nucleus starting at one week and four weeks post-defeat, respectively. Chronic intranasal treatment with OXT had a negative effect on sociability and mesolimbic OXTR binding in non-defeated females. However, chronic intranasal OXT promoted social engagement and increased mesolimbic OXTR binding in defeated females but not males. SSRI treatment led to only modest effects. This study identifies a sex-specific and stress-dependent function of intranasal OXT on mesolimbic OXTR and social behaviors.

Performance and paroxetine stability in tablets manufactured by fused deposition modelling-based 3D printing

OBJECTIVES

The objective of this study was to develop a method for the preparation and characterization of paroxetine (PRX) tablets, obtained by coupling hot-melt extrusion and fused deposition modelling (FDM)-based three-dimensional printing (3DP) technology. The impact of the printing process parameters on the drug stability and on the tablets performance was assessed.

METHODS

Tablets were obtained by FDM of hot-melt extruded PRX-loaded filaments. Physicochemical, thermal, spectroscopic, diffractometric analysis and in-vitro dissolution tests of the intermediate products and the finished dosage forms were performed.

KEY FINDINGS

The characterization of printed tablets evidenced mass and dimensions uniformity, and consistency of drug content and dissolution profile. The formation of amorphous solid dispersions and interaction of formulation components throughout the manufacturing process were demonstrated. Layer thickness, printing temperature, printing and travelling speeds, and infill were the most impacting process parameters on both the physicochemical properties and the in-vitro performance of the 3D-printed tablets.

CONCLUSIONS

PRX tablets, meeting compendial limits, were manufactured by 3DP, envisaging their clinical use as individually designed dosage forms. The assessment of the impact of processing parameters on the printed tablets provided insights, which will ultimately allow streamlining of the 3D process set-up for quicker and easier production of patient-centric medicines.

Oral Yohimbine as a New Probe Drug to Predict CYP2D6 Activity: Results of a Fixed-Sequence Phase I Trial

Objective

Yohimbine pharmacokinetics were determined after oral administration of a single oral dose of yohimbine 5 mg and a microdose of yohimbine 50 µg in relation to different cytochrome P450 (CYP) 2D6 genotypes. The CYP2D6 inhibitor paroxetine was used to investigate the influence on yohimbine pharmacokinetics. Microdosed midazolam was applied to evaluate a possible impact of yohimbine on CYP3A activity and the possibility of combining microdosed yohimbine and midazolam to simultaneously determine CYP2D6 and CYP3A activity.

Methods

In a fixed-sequence clinical trial, 16 healthy volunteers with a known CYP2D6 genotype [extensive (10), intermediate (2) and poor (4) metaboliser] received an oral dose of yohimbine 50 µg, yohimbine 5 mg at baseline and during paroxetine as a CYP2D6 inhibitor. Midazolam (30 µg) was co-administered to determine CYP3A activity at each occasion. Plasma concentrations of yohimbine, its main metabolite 11-OH-yohimbine, midazolam and paroxetine were quantified using validated liquid chromatography-tandem mass spectrometry assays.

Results

Pharmacokinetics of yohimbine were highly variable and a CYP2D6 genotype dependent clearance was observed. After yohimbine 5 mg, the clearance ranged from 25.3 to 15,864 mL/min and after yohimbine 50 µg, the clearance ranged from 39.6 to 38,822 mL/min. A more than fivefold reduction in clearance was caused by paroxetine in CYP2D6 extensive metabolisers, while the clearance in poor metabolisers was not affected. Yohimbine did not alter CYP3A activity as measured by microdosed midazolam.

Conclusions

The pharmacokinetics of yohimbine were highly correlated with CYP2D6, which was further supported by the clearance inhibition caused by the CYP2D6 inhibitor paroxetine. With these data, yohimbine is proposed to be a suitable probe drug to predict CYP2D6 activity. In addition, the microdose can be used in combination with microdosed midazolam to simultaneously evaluate CYP2D6 and CYP3A activity without any interaction between the probe drugs and because the microdoses exert no pharmacological effects.

Clinical Trial Registration

EudraCT2017-001801-34.

Electronic supplementary material

The online version of this article (10.1007/s40262-020-00862-6) contains supplementary material, which is available to authorized users.

Selective Serotonin Reuptake Inhibitors and Adverse Effects: A Narrative Review

Depression is the most prevalent psychiatric disorder in the world, affecting 4.4% of the global population. Despite an array of treatment modalities, depressive disorders remain difficult to manage due to many factors. Beginning with the introduction of fluoxetine to the United States in 1988, selective serotonin reuptake inhibitors (SSRIs) quickly became a mainstay of treatment for a variety of psychiatric disorders. The primary mechanism of action of SSRIs is to inhibit presynaptic reuptake of serotonin at the serotonin transporter, subsequently increasing serotonin at the postsynaptic membrane in the serotonergic synapse. The six major SSRIs that are marketed in the USA today, fluoxetine, citalopram, escitalopram, paroxetine, sertraline, and fluvoxamine, are a group of structurally unrelated molecules that share a similar mechanism of action. While their primary mechanism of action is similar, each SSRI has unique pharmacokinetics, pharmacodynamics, and side effect profile. One of the more controversial adverse effects of SSRIs is the black box warning for increased risk of suicidality in children and young adults aged 18–24. There is a lack of understanding of the complexities and interactions between SSRIs in the developing brain of a young person with depression. Adults, who do not have certain risk factors, which could be confounding factors, do not seem to carry this increased risk of suicidality. Ultimately, when prescribing SSRIs to any patient, a risk–benefit analysis must factor in the potential treatment effects, adverse effects, and dangers of the illness to be treated. The aim of this review is to educate clinicians on potential adverse effects of SSRIs.

Simultaneous enantio- and diastereo-selective high-performance liquid chromatography separation of paroxetine on an immobilized amylose-based chiral stationary phase under green reversed-phase conditions

A simple and green high-performance liquid chromatography method for the separation of paroxetine from its enantiomeric and diastereomeric impurities has been developed. The simultaneous chromatographic resolution was carried out on the amylose-based Chiralpak IA-3 chiral stationary phase using the mixture ethanol-water-diethylamine 80:20:0.1 (v/v/v) as a mobile phase. The effects of substitution of ethanol with methanol or acetonitrile and changes in column temperature on selectivity have been carefully investigated. The optimized single-run HPLC protocol allows the baseline separation of the enantiomers of paroxetine without suffering from interference from five other chiral and achiral impurities reported in the monograph of the European Pharmacopoeia.

Assessment of Paroxetine Molecular Interactions with Selected Monoamine and γ-Aminobutyric Acid Transporters

Thus far, many hypotheses have been proposed explaining the cause of depression. Among the most popular of these are: monoamine, neurogenesis, neurobiology, inflammation and stress hypotheses. Many studies have proven that neurogenesis in the brains of adult mammals occurs throughout life. The generation of new neurons persists throughout adulthood in the mammalian brain due to the proliferation and differentiation of adult neural stem cells. For this reason, the search for drugs acting in this mechanism seems to be a priority for modern pharmacotherapy. Paroxetine is one of the most commonly used antidepressants. However, the exact mechanism of its action is not fully understood. The fact that the therapeutic effect after the administration of paroxetine occurs after a few weeks, even if the levels of monoamine are rapidly increased (within a few minutes), allows us to assume a neurogenic mechanism of action. Due to the confirmed dependence of depression on serotonin, norepinephrine, dopamine and γ-aminobutyric acid levels, studies have been undertaken into paroxetine interactions with these primary neurotransmitters using in silico and in vitro methods. We confirmed that paroxetine interacts most strongly with monoamine transporters and shows some interaction with γ-aminobutyric acid transporters. However, studies of the potency inhibitors and binding affinity values indicate that the neurogenic mechanism of paroxetine's action may be determined mainly by its interactions with serotonin transporters.

Development and evaluation of a physiologically based pharmacokinetic model to predict carvedilol-paroxetine metabolic drug-drug interaction in healthy adults and its extrapolation to virtual chronic heart failure patients for dose optimization

Purpose: The metabolic drug-drug interactions (mDDIs) are one of the most important challenges faced by the pharmaceutical industry during the drug development stage and are frequently associated with labeling restrictions and withdrawal of drugs. The capacity of physiologically based pharmacokinetic (PBPK) models to absorb and upgrade with the newly available information on drug and population-specific parameters, makes them a preferred choice over the conventional pharmacokinetic models for predicting mDDIs.Method: A PBPK model capable of predicting the stereo-selective disposition of carvedilol after administering paroxetine by incorporating mechanism (time) based inhibition of CYP2D6 and CYP3A4 was developed by using the population-based absorption, distribution, metabolism and elimination (ADME) simulator, Simcyp®.Results: The model predictions for both carvedilol enantiomers were in close agreement with the observed PK data, as the ratios for observed/predicted PK parameters were within the 2-fold error range. The developed PBPK model was successful in capturing an increase in exposures of R and S-carvedilol, due to the time-based inhibition of CYP2D6 enzyme caused by paroxetine.Conclusion: The developed model can be used for exploring complex clinical scenarios, where multiple drugs are given concurrently, particularly in diseased populations where no clinical trial data is available.

Diazepam causes sedative rather than anxiolytic effects in C57BL/6J mice

Diazepam has been broadly accepted as an anxiolytic drug and is often used as a positive control in behavioral experiments with mice. However, as opposed to this general assumption, the effect of diazepam on mouse behavior can be considered rather controversial from an evidence point of view. Here we revisit this issue by studying the effect of diazepam on a benchmark task in the preclinical anxiety literature: the elevated plus maze. We evaluated the minute-by-minute time-course of the diazepam effect along the 10 min of the task at three different doses (0.5, 1 and 2 mg/kg i.p. 30 min before the task) in female and male C57BL/6J mice. Furthermore, we contrasted the effects of diazepam with those of a selective serotoninergic reuptake inhibitor (paroxetine, 10 mg/kg i.p. 1 h before the task). Diazepam had no anxiolytic effect at any of the tested doses, and, at the highest dose, it impaired locomotor activity, likely due to sedation. Noteworthy, our results held true when examining male and female mice separately, when only examining the first 5 min of the task, and when animals were subjected to one hour of restrain-induced stress prior to diazepam treatment. In contrast, paroxetine significantly reduced anxiety-like behavior without inducing sedative effects. Our results therefore suggest that preclinical studies for screening new anxiolytic drugs should be cautious with diazepam use as a potential positive control.

A group of cationic amphiphilic drugs activates MRGPRX2 and induces scratching behavior in mice

BACKGROUND

Mas gene-related G protein-coupled receptors (MRGPRs) are a G protein-coupled receptor family responsive to various exogenous and endogenous agonists, playing a fundamental role in pain and itch sensation. The primate-specific family member MRGPRX2 and its murine orthologue MRGPRB2 are expressed by mast cells mediating IgE-independent signaling and pseudoallergic drug reactions.

OBJECTIVES

Our aim was to increase knowledge about the function and regulation of MRGPRX2/MRGPRB2, which is of major importance in prevention of drug hypersensitivity reactions and drug-induced pruritus.

METHODS

To identify novel MRGPR (ant)agonists, we screened a library of pharmacologically active compounds by utilizing a high-throughput calcium mobilization assay. The identified hit compounds were analyzed for their pseudoallergic and pruritogenic effects in mice and human.

RESULTS

We found a class of commonly used drugs activating MRGPRX2 that, to a large extent, consists of antidepressants, antiallergic drugs, and antipsychotics. Three-dimensional pharmacophore modeling revealed structural similarities of the identified agonists, classifying them as cationic amphiphilic drugs. Mast cell activation was investigated by using the 3 representatively selected antidepressants clomipramine, paroxetine, and desipramine. Indeed, we were able to show a concentration-dependent activation and MRGPRX2-dependent degranulation of the human mast cell line LAD2 (Laboratory of Allergic Diseases-2). Furthermore, clomipramine, paroxetine, and desipramine were able to induce degranulation of human skin and murine peritoneal mast cells. These substances elicited dose-dependent scratching behavior following intradermal injection into C57BL/6 mice but less so in MRGPRB2-mutant mice, as well as wheal-and-flare reactions following intradermal injections in humans.

CONCLUSION

Our results contribute to the characterization of structure-activity relationships and functionality of MRGPRX2 ligands and facilitate prediction of adverse reactions such as drug-induced pruritus to prevent severe drug hypersensitivity reactions.

Paroxetine-Overview of the Molecular Mechanisms of Action

In the 21st century and especially during a pandemic, the diagnosis and treatment of depression is an essential part of the daily practice of many family doctors. It mainly affects patients in the age category 15–44 years, regardless of gender. Anxiety disorders are often diagnosed in children and adolescents. Social phobias can account for up to 13% of these diagnoses. Social anxiety manifests itself in fear of negative social assessment and humiliation, which disrupts the quality of social functioning. Treatment of the above-mentioned disorders is based on psychotherapy and pharmacotherapy. Serious side effects or mortality from antidepressant drug overdose are currently rare. Recent studies indicate that paroxetine (ATC code: N06AB), belonging to the selective serotonin reuptake inhibitors, has promising therapeutic effects and is used off-label in children and adolescents. The purpose of this review is to describe the interaction of paroxetine with several molecular targets in various points of view including the basic chemical and pharmaceutical properties. The central point of the review is focused on the pharmacodynamic analysis based on the molecular mechanism of binding paroxetine to various therapeutic targets.

Prescribed drugs containing nitrogen heterocycles: an overview

Heteroatoms as well as heterocyclic scaffolds are frequently present as the common cores in a plethora of active pharmaceuticals natural products. Statistically, more than 85% of all biologically active compounds are heterocycles or comprise a heterocycle and most frequently, nitrogen heterocycles as a backbone in their complex structures. These facts disclose and emphasize the vital role of heterocycles in modern drug design and drug discovery. In this review, we try to present a comprehensive overview of top prescribed drugs containing nitrogen heterocycles, describing their pharmacological properties, medical applications and their selected synthetic pathways. It is worth mentioning that the reported examples are actually limited to current top selling drugs, being or containing N-heterocycles and their synthetic information has been extracted from both scientific journals and the wider patent literature.

How Can Drug Metabolism and Transporter Genetics Inform Psychotropic Prescribing?

Many genetic variants in drug metabolizing enzymes and transporters have been shown to be relevant for treating psychiatric disorders. Associations are strong enough to feature on drug labels and for prescribing guidelines based on such data. A range of commercial tests are available; however, there is variability in included genetic variants, methodology, and interpretation. We herein provide relevant background for understanding clinical associations with specific variants, other factors that are relevant to consider when interpreting such data (such as age, gender, drug-drug interactions), and summarize the data relevant to clinical utility of pharmacogenetic testing in psychiatry and the available prescribing guidelines. We also highlight areas for future research focus in this field.

Spontaneous Ejaculation: A Focused Review for the Clinicians

INTRODUCTION

The process of ejaculation has important meanings not only for its association with orgasm but also for the timing to ejaculate in the context of sexual activity. Spontaneous (involuntary) ejaculation (SE) without any sexual stimulation is a distressing symptom. Our understanding of SE is limited. Unfortunately, many physicians are not aware of these cases.

OBJECTIVES

The objective of this study is to describe the etiopathogenesis, clinical features, diagnosis, and treatment options for SE.

METHODS

We searched the literature for publications on "SE," "spontaneous emission" or "involuntary ejaculation," and factors influencing SE in the PUBMED/MEDLINE, Scopus, Cochrane Library, EMBASE, PsycINFO, ProQuest, Academic Search Complete database, Google Scholar, and CINAHL databases from inception to August 2020.

RESULTS

The literature search yielded 36 relevant publications reporting on 43 patients with SE. Attempts to explain the cause of pathologic SE have included 4 etiological groups (spinal cord lesions, psychological causes, rabies, and drug-induced). The underlying mechanisms responsible for induction of SE may include increased adrenergic activity, overactivity in dopaminergic system, decreased serotonergic activity, damage of descending inhibitory pathway, or penile hyperexcitability. SE may occur in the absence of an identifiable trigger or may be triggered by non-sexual circumstances (micturition, defecation, glans touch, anxiety, panic attack, or school examinations). Treatment options include psychoanalytic treatment, paroxetine, citalopram, sertraline, silodosin, and anxiolytics. In drug-induced SE, dose reduction and drug withdrawal with or without switching to another drug may relief SE.

CONCLUSIONS

SE is one of the least reported ejaculatory dysfunction. The key feature shared in common by these men is SE without any sexual thoughts or fantasies, may be triggered by non-sexual contexts, rarely associated with orgasm or erection. Treatment by psychoanalytic treatment and pharmacotherapy may be helpful. Further research might explore the definite underlying mechanisms. Abdel-Hamid IA, Ali OI. Spontaneous Ejaculation: A Focused Review for the Clinicians. Sex Med Rev 2021;9:406-422.

Joint replenishment of zinc and folic acid enhances the anti-depressive effect of paroxetine via increasing serum calcium and copper and decreasing serum arsenic

Insufficient zinc and folic acid levels are associated with depression and poor response to antidepressants. This study aimed to investigate the influences of combined zinc and folic acid replenishment on the anti-depressive effect of paroxetine. Male rats were randomly divided into five groups: control (C), model (M), paroxetine (MP), zinc + folic acid (MZnF), and zinc + folic acid + paroxetine (MZnFP) groups. Rats were exposed to mild unpredictable stress for 3 weeks as a depression model. The combinations of drug and supplements were applied via daily gavage for 4 weeks. The open field test was conducted to observe behavioral changes. A chemiluminescence method was used to detect folacin, and inductively coupled plasma mass spectrometry was used to detect serum elements. Supplementation of zinc and folic acid significantly improved behavior responses to paroxetine, including movement speed, total distance, and central zone frequency. In addition, higher calcium and copper levels and a lower arsenic level were found in the serum of the MZnFP group. Thus, supplementation of zinc and folacin can enhance the anti-depressive effect of paroxetine, and the mechanism is potentially related to the improved levels of calcium and copper and a reduced level of arsenic.

Inverse in silico-in vitro fishing of unexpected paroxetine kinase targets from tumor druggable kinome

The serotonin selective reuptake inhibitor paroxetine has been clinically observed to reposition a significant suppressing potency on human tumors by unexpectedly targeting diverse kinase pathways involved in tumorigenesis. Here, we describe an inverse in silico-in vitro strategy to fish potential kinase targets using the paroxetine as bait. This is different (inverse) to the traditional drug discovery process that commonly screens small-molecule inhibitors for a specific kinase target. In the procedure, cell viability assays demonstrate that paroxetine has strong cytotoxicity on human tumor cell lines. Various protooncogene protein kinases are ontologically/manually enriched to define a druggable kinome, and a systematic interaction profile of paroxetine with the kinome is created, which indicates that paroxetine can potentially bind to some known targets or key regulators of human tumors. Kinase assays determine that paroxetine can effectively inhibit c-Src family kinases at nanomolar or micromolar levels. It is observed that the paroxetine ligand forms a tightly packed interface against the active site of these unexpected kinase targets to constitute several specific hydrogen bonds/π-π/cation-π stackings and a number of nonspecific hydrophobic/vdW contacts, while exposing a portion of molecular surface to solvent. More significantly, the ligand adopts two distinct binding modes (i.e., class I and class II) to interact with different kinases; the class-I mode has a higher stability and inhibitory activity than class-II mode. Steric clash seems to cause the ligand flipping from class I to class II. Graphical abstract.

Identification of annotated bioactive molecules that impair motility of the blood fluke Schistosoma mansoni

Neglected tropical diseases are of growing worldwide concern and schistosomiasis, caused by parasitic flatworms, continues to be a major threat with more than 200 million people requiring preventive treatment. As praziquantel (PZQ) remains the treatment of choice, an urgent need for alternative treatments motivates research to identify new lead compounds that would complement PZQ by filling the therapeutic gaps associated with this treatment. Because impairing parasite neurotransmission remains a core strategy for control of parasitic helminths, we screened a library of 708 compounds with validated biological activity in humans on the blood fluke Schistosoma mansoni, measuring their effect on the motility on schistosomulae and adult worms. The primary phenotypic screen performed on schistosomulae identified 70 compounds that induced changes in viability and/or motility. Screening different concentrations and incubation times identified molecules with fast onset of activity on both life stages at low concentration (1 μM). To complement this study, similar assays were performed with chemical analogs of the cholinomimetic drug arecoline and the calcilytic molecule NPS-2143, two compounds that rapidly inhibited schistosome motility; 17 arecoline and 302 NPS-2143 analogs were tested to enlarge the pool of schistosomicidal molecules. Finally, validated hit compounds were tested on three functionally-validated neuroregulatory S. mansoni G-protein coupled receptors (GPCRs): Sm5HTR (serotonin-sensitive), SmGPR2 (histamine) and SmD2 (dopamine), revealing NPS-2143 and analogs as potent inhibitors of dopamine/epinine responses on both human and S. mansoni GPCRs. This study highlights the potential for repurposing known human therapeutic agents for potential schistosomicidal effects and expands the list of hits for further progression.