A placebo-controlled trial of dextromethorphan as an adjunct in opioid-dependent patients undergoing methadone maintenance treatment

Add-On Dextromethorphan Improves the Effects of Pirfenidone in Bleomycin-Treated Mice and Patients With Pulmonary Fibrosis

BACKGROUND AND OBJECTIVE

Idiopathic pulmonary fibrosis is a progressive interstitial lung disease characterised by excessive activation of myofibroblasts. However, currently available antifibrotic drugs exhibit limited efficacy. The dysregulation of redox processes plays a significant role in the pathogenesis of idiopathic pulmonary fibrosis. Dextromethorphan (DM) is used in the treatment of various inflammation-related diseases. This study aimed to investigate the effectiveness of the combination of DM and pirfenidone (PFD) in treating idiopathic pulmonary fibrosis in both animal models and humans.

METHODS

In a bleomycin-induced pulmonary fibrosis mouse model, the anti-fibrotic effects of DM and/or PFD were assessed by evaluating fibrotic area, hydroxyproline levels, and fibrotic markers. In a transforming growth factor-β1-induced cell model, proliferation, migration, fibrosis markers, and oxidative stress were analysed to elucidate the mechanisms underlying the anti-fibrotic actions of DM and/or PFD. Finally, the efficacy of DM combined with PFD in patients with pulmonary fibrosis was evaluated by comparing pulmonary imaging scores and pulmonary function before and after treatment in the PFD group and the PFD + DM group.

RESULTS

We observed that even ultralow doses of DM, either alone or in combination with PFD, demonstrated substantial protective effects in mice. Notably, administration of DM or combined drugs at 2 weeks after bleomycin modelling still showed anti-fibrotic effects. In vitro, DM monotherapy and combination therapy restored the redox balance by suppressing nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4/reactive oxygen species production and upregulating superoxide dismutase, contributing to their anti-fibrotic mechanisms. In the clinical study, add-on DM improved PFD in mitigating pulmonary function decline and improving chest high-resolution computed tomography imaging scores.

CONCLUSIONS

Ultralow doses of dextromethorphan significantly alleviate pulmonary fibrosis in bleomycin-treated mice through restoring the redox balance. Add-on DM improves the effects of PFD in both bleomycin-treated mice and patients with pulmonary fibrosis.

TRIAL REGISTRATION

ChiCTR2000037602.

Glial modulators as novel therapeutics for comorbid pain and opioid use disorder

Chronic pain and opioid use disorder (OUD) are major public health problems, with rising opioid-related overdose deaths linked to increased opioid prescriptions for pain management. Novel treatment approaches for these commonly comorbid disorders are needed. Growing evidence supports a role for glial activation for both chronic pain and substance use disorders, including OUD. This review provides an overview of glial modulators as a novel treatment approach for comorbid pain and OUD. We aim to synthesize clinical studies investigating the efficacy of glial modulators in treating these comorbid disorders. We conducted a literature search of PubMed and Google Scholar databases in October 2023 to identify relevant clinical trials. The included studies varied in terms of patient population, study methodology and outcomes assessed, and were often limited by small sample sizes and other methodological issues. Additionally, several glial modulators have yet to be studied for chronic pain and OUD. Despite these limitations, these studies yielded positive signals that merit further investigation. Both chronic pain and OUD remain significant public health problems, with many treatment challenges. Glial modulators continue to hold promise as novel therapeutics for comorbid pain and OUD, given positive indications that they can improve pain measures, and reduce addiction-related outcomes. As our understanding of the mechanisms underlying the contributions of glial modulators to pain and addiction behaviours deepens, we will be better equipped to identify more specific therapeutic targets for chronic pain and OUD.

Aerobic exercise as a promising nonpharmacological therapy for the treatment of substance use disorders

Despite the prevalence and public health impact of substance use disorders (SUDs), effective long-term treatments remain elusive. Aerobic exercise is a promising, nonpharmacological treatment currently under investigation as a strategy for preventing drug relapse. Aerobic exercise could be incorporated into the comprehensive treatment regimens for people with substance abuse disorders. Preclinical studies of SUD with animal models have shown that aerobic exercise diminishes drug-seeking behavior, which leads to relapse, in both male and female rats. Nevertheless, little is known regarding the effects of substance abuse-induced cellular and physiological adaptations believed to be responsible for drug-seeking behavior. Accordingly, the overall goal of this review is to provide a summary and an assessment of findings to date, highlighting evidence of the molecular and neurological effects of exercise on adaptations associated with SUD.

Inflammatory Biomarkers in Addictive Disorders

Substance use disorders are a group of diseases that are associated with social, professional, and family impairment and that represent a high socio-economic impact on the health systems of countries around the world. These disorders present a very complex diagnosis and treatment regimen due to the lack of suitable biomarkers supporting the correct diagnosis and classification and the difficulty of selecting effective therapies. Over the last few years, several studies have pointed out that these addictive disorders are associated with systemic and central nervous system inflammation, which could play a relevant role in the onset and progression of these diseases. Therefore, identifying different immune system components as biomarkers of such addictive disorders could be a crucial step to promote appropriate diagnosis and treatment. Thus, this work aims to provide an overview of the immune system alterations that may be biomarkers of various addictive disorders.

N-Substituted-3-alkoxy-derivatives of dextromethorphan are functional NMDA receptor antagonists in vivo: Evidence from an NMDA-induced seizure model in rats

Interest in developing NMDA receptor antagonists with reduced side-effects for neurological and psychiatric disorders has been re-energized by the recent introduction of esketamine into clinical practice for treatment-resistant depression. Structural analogs of dextromethorphan bind with low affinity to the NMDA receptor ion channel, have functional effects in vivo, and generally display a lower propensity for side-effects than that of ketamine and other higher affinity antagonists. As such, the aim of the present study was to determine whether a series of N-substituted-3-alkoxy-substituted dextromethorphan analogs produce their anticonvulsant effects through NMDA receptor blockade. Compounds were studied against NMDA-induced seizures in rats. Compounds were administered intracerebroventricularly in order to mitigate confounds of drug metabolism that arise from systemic administration. Comparison of the anticonvulsant potencies to their affinities for NMDA, σ1, and σ2 binding sites were made in order to evaluate the contribution of these receptors to anticonvulsant efficacy. The potencies to block convulsions were positively associated with their affinities to bind to the NMDA receptor ion channel ([3H]-TCP binding) (r = 0.71, p < 0.05) but not to σ1 receptors ([3H]-SKF 10047 binding) (r = -0.31, p = 0.46) or to σ2 receptors ([3H]-DTG binding) (p = -0.38, p = 0.36). This is the first report demonstrating that these dextromethorphan analogs are functional NMDA receptor antagonists in vivo. Given their potential therapeutic utility and favorable side-effect profiles, such low affinity NMDA receptor antagonists could be considered for further development in neurological (e.g., anticonvulsant) and psychiatric (e.g., antidepressant) disorders.

Clinical benefits and risks of N-methyl-d-aspartate receptor antagonists to treat severe opioid use disorder: A systematic review

BACKGROUND

Demand for treatments for severe opioid use disorder is increasing worldwide. The current pharmacotherapy is mainly focused on opioid and adrenergic receptors. The N-methyl-d-aspartate receptor (NMDAR) is among other receptors that can also be targeted to treat the disease. Findings from randomized controlled trials (RTCs) on NMDAR antagonists to treat severe opioid use disorder amply varied. This study aimed to evaluate the clinical benefits and assess the potential risks for adverse events or side effects of NMDAR antagonists that were investigated for the treatment of severe opioid use disorder.

METHODS

Articles were searched in PubMed, Scopus, Google Scholar, Proquest. Cochrane Review Database, Medline Ovid, and EMBASE from their inception to March 2019. RTCs on NMDAR antagonists for the treatment of severe opioid use disorder were independently screened and assessed by two authors. The results were synthesized qualitatively.

RESULTS

Nineteen RTCs of 1459 participants met the inclusion criteria. There is moderate evidence suggesting that ketamine, memantine, amantadine, and dextromethorphan may be able to manage opioid withdrawal symptoms. There is little evidence suggesting that memantine may be able to reduce methadone maintenance dose in participants on methadone, reduce opioid use, and reduce craving. Dropout is noticeable among dextromethorphan's participants. Safety concerns are more likely associated with dextromethorphan and ketamine.

CONCLUSIONS

NMDAR antagonists have the potentiality to treat severe opioid use disorder. There is insufficient evidence to recommend them for the treatment of severe opioid use disorder due to several limitations inherent to the RCTs reviewed. Further exploration is needed.

Comparing the Efficacy of Anodal, Cathodal, and Sham Transcranial Direct Current Stimulation on Brain-Derived Neurotrophic Factor and Psychological Symptoms in Opioid-Addicted Patients

Introduction:

Today, addiction to opioids is a serious problem all over the world. Unfortunately, the consumption of these drugs and the number of addicted people have drastically increased. This research aimed at comparing the efficacy of anodal, cathodal, and sham transcranial Direct Current Stimulation (tDCS) on the Brain-Derived Neurotrophic Factor (BDNF) and psychological symptoms in opioid-addicted patients.

Methods:

Thirty opioid-addicted patients were selected based on the Diagnostic and Statistical Manual of Mental Disorders, the Fifth Edition, through the convenience sampling method. They were then randomly assigned to 3 groups (10 in each group). The subjects were evaluated before and after tDCS by their serum level of BDNF, desires for drug questionnaire, and depression anxiety stress scale. The data were analyzed by the Kolmogorov-Smirnov test, one-way analysis of variance, as well as the Bonferroni test.

Results:

Stimulating the Dorsolateral Prefrontal Cortex (DLPFC) led to a significant change in increasing the level of BDNF (P=0.031) and reducing the degree of depression (P=0.018), anxiety (P=0.001), stress (P=0.012), and decreased the level of craving (P=0.001) in opioid-addicted patients. There was no significant difference between active stimulation groups (anodal left/cathodal right and anodal right/cathodal left). The stimulation of the right DLPFC (group B) significantly increased BDNF in comparison with the sham group (sham tDCS) and decreased anxiety and craving. Nonetheless, no change was observed in depression and stress. The stimulation of the left DLPFC (group A) significantly reduced depression, anxiety, stress, and craving compared with the sham group, while there was no change in BDNF.

Conclusion:

In addition to the conventional treatments of opioid-addicted patients, tDCS is an effective complementary treatment.

Peripheral levels of BDNF and opiate-use disorder: literature review and update

Several neurobiological factors are related to opiate-use disorder (OUD), and among them, neurotrophins have a relevant role. Brain-derived neurotrophic factor (BDNF) is a central neurotrophin involved in many neuronal processes, and it has been related to several psychiatric diseases and addictive disorders. BDNF can be measured in plasma and serum; its levels may reflect BDNF concentrations in the central nervous system (CNS) and, indirectly, CNS processes. Hence, peripheral BDNF could be a biomarker in clinical practice. This manuscript explores the findings about peripheral BDNF and OUD in humans. Opiates induce neurotoxicity in the CNS, which may be correlated with modifications in BDNF expression. Thus, basal levels of peripheral BDNF in OUD patients may be altered, which could be modified with abstinence. Also, opiates may modify epigenetic processes that may be associated with peripheral concentrations of BDNF, and in this line, withdrawal could reflect recovering processes in the CNS. Additionally, treatment modifies the peripheral concentrations of BDNF, but the clinical implications of those changes are yet not elucidated. No specific conclusion can be performed and more investigation in this area is necessary to elucidate the real potential of peripheral BDNF as a biomarker.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Clozapine metabolites protect dopaminergic neurons through inhibition of microglial NADPH oxidase

Background

Clozapine, an atypical antipsychotic medication, has been effectively used to treat refractory schizophrenia. However, the clinical usage of clozapine is limited due to a high incidence of neutropenia or agranulocytosis. We previously reported that clozapine protected dopaminergic neurons through inhibition of microglial activation. The purpose of this study was to explore the neuroprotective effects of clozapine metabolites clozapine N-oxide (CNO) and N-desmethylclozapine (NDC), as well as their propensity to cause neutropenia.

Methods

The primary midbrain neuron-glia culture was applied to detect the neuroprotective and anti-inflammatory effect of clozapine and its metabolites in lipopolysaccharide (LPS) and MPP⁺-induced toxicity. And the subsequent mechanism was demonstrated by gp91^phox mutant cell cultures as well as microgliosis cell lines. In vivo, to confirm the neuroprotective effect of clozapine and CNO, we measured the dopaminergic neuronal loss and rotarod motor deficits in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-generated mouse Parkinson’s disease (PD) model. The neutropenia or agranulocytosis of clozapine and its metabolites was illustrated by white blood cell count of the treated mice.

Results

We found that, in midbrain neuron-glia cultures, CNO and NDC were more potent than clozapine in protecting dopaminergic neurons against LPS and MPP⁺-induced toxicity. CNO and NDC-afforded neuroprotection was linked to inhibition of microglia-mediated neuroinflammation, as demonstrated by abolished neuroprotection in microglia-depleted cultures and their capacity of inhibiting LPS-induced release of proinflammatory factors from activated microglia. NADPH oxidase (NOX2) was subsequently recognized as the main target of CNO and NDC since genetic ablation of gp91^phox, the catalytic subunit of NOX2, abolished their neuroprotective effects. CNO and NDC inhibited NOX2 activation through interfering with the membrane translocation of the NOX2 cytosolic subunit, p47^phox. The neuroprotective effects of CNO were further verified in vivo as shown by attenuation of dopaminergic neurodegeneration, motor deficits, and reactive microgliosis in MPTP-generated mouse PD model. More importantly, unlike clozapine, CNO did not lower the white blood cell count.

Conclusions

Altogether, our results show that clozapine metabolites elicited neuroprotection through inactivation of microglia by inhibiting NOX2. The robust neuroprotective effects and lack of neutropenia suggest that clozapine metabolites may be promising candidates for potential therapy for neurodegenerative diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0573-z) contains supplementary material, which is available to authorized users.

Brain-derived neurotrophic factor serum levels in heroin-dependent patients after 26weeks of withdrawal

BACKGROUND

Brain-derived neurotrophic factor (BDNF) has been implicated in the pathophysiology of heroin dependence. BDNF expression is dramatically changed during drug withdrawal, and is associated with drug withdrawal syndrome. This study aimed to explore (1) alterations of BDNF serum levels in heroin-dependent patients after long term abstinence; and (2) the association between BDNF serum levels and protracted withdrawal syndrome.

METHOD

Fifty-three male heroin-dependent patients and fifty-two gender-matched healthy controls were enrolled in this study. We measured BDNF serum levels at baseline and 26 weeks after heroin abstinence. Moreover, protracted withdrawal symptoms, depression and anxiety symptoms were measured by Protracted Withdrawal Symptoms of Heroin-dependent patients (PWSHA), Self-rating Depression Scale (SDS) and Self-rating Anxiety Scale (SAS), respectively.

RESULT

We found that baseline BDNF serum levels were significantly lower in heroin-dependent patients compared to controls (p<0.01). There was also a significantly difference in BDNF serum levels among heroin-dependent patients at baseline and 26-week follow-up (p<0.01). The BDNF serum levels were not associated with age, BMI, years of education, age of initial use, or duration of use. Of the clinical symptoms measured, the change in BDNF serum levels from baseline to 26-week follow-up was negatively associated with the change in PWSHA scores (r = -0.44, p<0.01, see Table 2 and Figure 2 for details).

CONCLUSION

The results show that the BDNF serum levels in heroin-dependent patients are lower than those of healthy controls at baseline and increased after 26 weeks of abstinence, although the BDNF serum levels are still lower than those of the healthy controls. A negative correlation between the change in BDNF serum levels and protracted withdrawal symptoms was found but needs to be confirmed in further study. The results revealed that BDNF serum level is worth paying attention to in order to further investigate the possibility of it being a biomarker of treatment outcome for opiate dependence.