An open-label multicenter study to assess the safety of dextromethorphan/quinidine in patients with pseudobulbar affect associated with a range of underlying neurological conditions

Behavioral disorders in multiple sclerosis: a comprehensive review

Multiple sclerosis (MS) is a heterogenous autoimmune-mediated disease of the central nervous system (CNS) characterized by inflammation, demyelination and chronic progressive neurodegeneration. Among its broad and unpredictable range of neuropsychiatric symptoms, behavioral changes are common, even from the early stages of the disease, while they are associated with cognitive deficits in advanced MS. According to DSM-5, behavioral disorders include attention deficits, oppositional, defiant and conduct disorders, anxiety, panic, obsessive-compulsive disorders (OCD), disruptive and emotional disorders, while others include also irritability, agitation, aggression and executive dysfunctions. Approximately 30 to 80% of individuals with MS demonstrate behavioral changes associated with disease progression. They are often combined with depression and other neuropsychiatric disorders, but usually not correlated with motor deficits, suggesting different pathomechanisms. These and other alterations contribute to disability in MS. While no specific neuropathological data for behavioral changes in MS are available, those in demyelination animal models share similarities with white matter and neuroinflammatory abnormalities in humans. Neuroimaging revealed prefrontal cortical atrophy, interhemispheric inhibition and disruption of fronto-striato-thalamic and frontoparietal networks. This indicates multi-regional patterns of cerebral disturbances within the MS pathology although their pathogenic mechanisms await further elucidation. Benefits of social, psychological, behavioral interventions and exercise were reported. Based on systematical analysis of PubMed, Google Scholar and Cochrane library, current epidemiological, clinical, neuroimaging and pathogenetic evidence are reviewed that may aid early identification of behavioral symptoms in MS, and promote new therapeutic targets and strategies.

ALSUntangled #71: Nuedexta

Nuedexta is a combination of dextromethorphan hydrobromide and quinidine sulfate and was approved by the Food and Drug Administration (FDA) in 2010 to treat pseudobulbar affect (PBA). There have since been anecdotal case reports of bulbar function improvements after Nuedexta treatment. Here, we review the off-label use of Nuedexta for improving bulbar function in people with ALS. Nuedexta has plausible mechanisms for protecting brain stem motor neurons via its effects on S1R and glutamate excitotoxicity. Recent clinical trials support that Nuedexta can improve bulbar function in PALS, with or without PBA. Nuedexta causes mild to moderate side effects. Based on this information, we support considering Nuedexta treatment for bulbar dysfunction in ALS patients with or without PBA.

Classics in Chemical Neuroscience: Dextromethorphan (DXM)

Dextromethorphan (DXM) was introduced in 1958 as the first non-opioid cough suppressant and is indicated for multiple psychiatric disorders. It has been the most used over-the-counter cough suppressant since its emergence. However, individuals quickly noticed an intoxicating and psychedelic effect if they ingested large doses. DXM's antagonism at N-methyl-d-aspartate receptors (NMDAr) is thought to underly its efficacy in treating acute cough, but supratherapeutic doses mimic the activity of dissociative hallucinogens, such as phencyclidine and ketamine. In this Review we will discuss DXM's synthesis, manufacturing information, drug metabolism, pharmacology, adverse effects, recreational use, abuse potential, and its history and importance in therapy to present DXM as a true classic in chemical neuroscience.

Pathological laughter and crying in neurological disorders: recognition and treatment

Pathological laughter and crying is a disabling symptom complex associated with damage to various central nervous system pathways that control the reflex motor component of emotional expression. Many underlying conditions-including neurodegenerative diseases, CNS inflammation, vascular lesions and traumatic brain injury-can be associated with disinhibition of emotional reflex control. This suggests a disruption of anatomical and functional networks, rather than any specific unifying pathological process. There is a wide differential diagnosis, including depression, dementia and other forms of behavioural disturbance. Diagnostic criteria and rating scales can help with clinical assessments and facilitate clinical trials. There is now good-quality evidence for a combination of dextromethorphan and quinidine, with weaker evidence for tricyclic and selective serotonin reuptake inhibitor antidepressants. Pathological laughter and crying is disabling and underdiagnosed but potentially treatable, and its wider recognition is important.

Effect of one-year dextromethorphan/quinidine treatment on management of respiratory impairment in amyotrophic lateral sclerosis

Treatment with Dextromethorphan/Quinidine (DM/Q) has demonstrated benefit on pseudobulbar affect and bulbar function in amyotrophic lateral sclerosis (ALS). The aim of this study was to assess whether DM/Q could provide long-term improvement in bulbar function and thereby prolong noninvasive respiratory management in ALS.

MATERIALS AND METHODS

This prospective, case-cohort study, recruited ALS patients with bulbar dysfunction. Subjects included were compared with cross-matched historical controls. Cases received DM/Q (20/10 mg twice daily) during one-year follow-up; bulbar dysfunction was evaluated with the Norris scale bulbar subscore (NBS) and bulbar subscale of AlSFRS-R (ALSFRSb).

RESULTS

In total, 21 cases and 20 controls were enrolled, of whom noninvasive respiratory muscle assistance failed in 6 (28.5%) patients in the DM/Q group, compared with 4 patients (20.0%) in the control group (p = 0.645). Time from study onset to failure of respiratory muscle aids was 5.50 + 1.31 months in the DM/Q group and 5.20 + 1.15 months in the control group (p = 0.663). The adjusted OR for the effect of treatment on failure of noninvasive respiratory muscle aids was 2.12 (95%CI 0.23-33.79, p = 0.592). In the DM/Q group an impairment in scores was found in NBS (F = 19.26, p = 0.000) and ALSFRS-Rb (F = 12.71, p = 0.001) across different months of the study.

CONCLUSION

Treatment with DM/Q in ALS is unable to prolong noninvasive respiratory management, and moreover, has no effect on long-term deterioration of bulbar function. Notwithstanding the results on bulbar function, DM/Q was found to improve pseudobulbar affect during one-year follow-up.

Mood Disorders and Anxiety in Parkinson's Disease: Current Concepts

Mood disorders and anxiety significantly impact the prognosis and disease course of Parkinson's disease. Non-motor symptoms of Parkinson's disease such as apathy, anhedonia, and fatigue overlap with diagnostic criteria for anxiety and depression, thus making accurate diagnosis of mood disorders in Parkinson's disease patients difficult. Furthermore, treatment options for mood disorders can produce motor complications leading to poor adherence and impaired quality of life in Parkinson's disease patients. This review aims to clarify the current state of diagnostic and treatment options pertaining to anxiety and mood disorders in Parkinson's disease. It explores both the pharmacologic and non-pharmacologic treatment modalities for various mood disorders in comorbid Parkinson's disease with a brief discussion of the future outlook of the field given the current state of the literature.

Irritability in Huntington's Disease

Huntington’s disease (HD) is a heritable and fatal neurodegenerative disease characterized by a triad of motor, cognitive and neuropsychiatric symptoms. A common and particularly detrimental neuropsychiatric alteration in HD gene carriers is irritability, which frequently manifests as abrupt and unpredictable outbursts of anger. This symptom increases the burden of HD in multiple ways, such as jeopardizing employment and straining familial or caregiver support. Although irritability in HD is diagnosed by the administration of standardized rating scales and clinical expertise, measurement of severity and progression is complicated by several factors. Currently, individuals with HD who present with irritability may be managed with a variety of psychotropic medications, primarily antidepressants and antipsychotics. While these therapies offer relief to individuals suffering from irritability in HD, they are often not sufficient. Here, we review irritability in the context of HD and emphasize the need for treatments that are better tailored to mitigate this troublesome symptom. An expeditious strategy in pursuit of this goal involves evaluating the efficacy of approved medications that are used to treat similar neuropsychiatric symptoms.

Progressive Supranuclear Palsy and Corticobasal Degeneration

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are neurodegenerative tauopathies with neuronal and glial lesions composed of tau that is composed predominantly of isomers with four repeats in the microtubule-binding domain (4R tau). The brain regions vulnerable to pathology in PSP and CBD overlap, but there are differences, particularly with respect to distribution of neuronal loss, the relative abundance of neuronal and glial lesions, the morphologic features of glial lesions, and the frequency of comorbid pathology. Both PSP and CBD have a wide spectrum of clinical manifestations, including disorders of movement and cognition. Recognition of phenotypic diversity in PSP and CBD may improve antemortem diagnostic accuracy, which tends to be very good for the most common presentation of PSP (Richardson syndrome), but poor for the most characteristic presentation of CBD (corticobasal syndrome: CBS). Development of molecular and imaging biomarkers may improve antemortem diagnostic accuracy. Currently, multidisciplinary symptomatic and supportive treatment with pharmacological and non-pharmacological strategies remains the standard of care. In the future, experimental therapeutic trials will be important to slow disease progression.

Progressive supranuclear palsy: Advances in diagnosis and management

Progressive supranuclear palsy (PSP) is a complex clinicopathologic disease with no current cure or disease modulating therapies that can only be definitively confirmed at autopsy. Growing understanding of the phenotypic diversity of PSP has led to expanded clinical criteria and new insights into etiopathogenesis that coupled with improved in vivo biomarkers makes increased access to current clinical trials possible. Current standard-of-care treatment of PSP is multidisciplinary, supportive and symptomatic, and several trials of potentially disease modulating agents have already been completed with disappointing results. Current ongoing clinical trials target the abnormal aggregation of tau through a variety of mechanisms including immunotherapy and gene therapy offer a more direct method of treatment. Here we review PSP clinicopathologic correlations, in vivo biomarkers including MRI, PET, and CSF biomarkers. We additionally review current pharmacologic and non-pharmacologic methods of treatment, prior and ongoing clinical trials in PSP. Newly expanded clinical criteria and improved specific biomarkers will aid in identifying patients with PSP earlier and more accurately and expand access to these potentially beneficial clinical trials.

Pharmacotherapy for the Pseudobulbar Affect in Individuals Who Have Sustained a Traumatic Brain Injury: a Systematic Review

Pseudobulbar affect is a debilitating condition that significantly reduces quality of life for many individuals following traumatic brain injury (TBI). It is characterized by embarrassing and often uncontrollable episodes of crying or laughter. The aim of this systematic review was to evaluate the effectiveness of pharmacotherapy as compared to all other comparators for the management of pseudobulbar affect in adults who have sustained TBI. Six databases were searched, with additional hand searching of journals, clinical trials registries and international drug regulators to identify published and unpublished studies in English up to June 2018. Studies were eligible for this review if they included adults who had sustained a medically confirmed TBI and presented with pseudobulbar affect. All pharmacotherapy and comparator interventions were considered for inclusion, and study design was not limited to randomised controlled trials. Evidence quality was assessed using Joanna Briggs Institute Critical Appraisal Instruments. Two quasi-experimental studies examining the effectiveness of dextrometamorphan/quinidine (DM/Q) were identified. These studies reported that DM/Q was effective in reducing symptoms of pseudobulbar affect and had a positive safety profile, over follow-up periods of 3 months (n = 87) and 12 months (n = 23). However, both studies were limited by lack of a control group and a high dropout rate. The findings of twelve case reports examining the effectiveness of DM/Q (n = 6) and anti-depressants (n = 6) are also discussed. Further research is required to determine which pharmacological interventions provide the best outcomes for individuals with pseudobulbar affect following TBI, with consideration given to side effect profiles and financial costs.

Pseudobulbar Affect in Parkinsonian Disorders: A Review

Pseudobulbar affect (PBA) is a neurological symptom of inappropriate and uncontrollable laughter or crying that occurs secondary to a variety of neurological conditions, including parkinsonian disorders. PBA is a socially and emotionally debilitating symptom that has been estimated to affect 3.6% to 42.5% of the population with Parkinson's disease. While indexing measures and treatment options for PBA have been extensively studied in neurological conditions such as amyotrophic lateral sclerosis and multiple sclerosis, there has been considerably less attention given in the literature to PBA in parkinsonian disorders. The purpose of this review is to discuss the pathophysiology of PBA, its prevalence and impact on quality of life in parkinsonian disorders, and the treatment options currently available. Areas requiring further study, including the development of standardized, cross-culturally validated methods of symptom assessment, and evidence-based studies exploring the efficacy of current treatment options in parkinsonian disorders, are also highlighted.

Pharmacotherapy for the pseudobulbar affect in individuals who have sustained a traumatic brain injury: a systematic review protocol

REVIEW OBJECTIVE/QUESTION

The objective of this systematic review is to synthesize current evidence on the effectiveness of pharmacotherapy as compared to all comparators for the management of pseudobulbar affect in adults 16 years and over who have sustained a traumatic brain injury. The specific review question is: What is the effectiveness of pharmacotherapy for the management of pseudobulbar affect in adults 16 years and over who have sustained a traumatic brain injury?

Hypothalamic relapse of a cardiac large B-cell lymphoma presenting with memory loss, confabulation, alexia-agraphia, apathy, hypersomnia, appetite disturbances and diabetes insipidus

A 37-year-old Hispanic man with a right atrial intracardiac mass diagnosed as diffuse large B-cell lymphoma (DLBCL) was successfully treated with surgery and chemotherapy. During 4 years, several total-body positron emission tomography and MRI scans showed no extracardiac lymphoma. On year 5 after the cardiac surgery, patient presented with sleepiness, hyperphagia, memory loss, confabulation, dementia and diabetes insipidus. Brain MRI showed a single hypothalamic recurrence of the original lymphoma that responded to high-dose methotrexate treatment. Correction of diabetes insipidus improved alertness but amnesia and cognitive deficits persisted, including incapacity to read and write. This case illustrates two unusual locations of DLBCL: primary cardiac lymphoma and hypothalamus. We emphasise the importance of third ventricle tumours as causing amnesia, confabulation, behavioural changes, alexia-agraphia, endocrine disorders and alterations of the circadian rhythm of wakefulness-sleep secondary to lesions of specific hypothalamic nuclei and disruption of hypothalamic-thalamic circuits.

Dextromethorphan/Quinidine for Pseudobulbar Affect Following Stroke: Safety and Effectiveness in the PRISM II Trial

BACKGROUND

Dextromethorphan (DM) / quinidine (Q) was approved for pseudobulbar affect (PBA) treatment based on efficacy and safety trials in patients with PBA caused by amyotrophic lateral sclerosis or multiple sclerosis. The PRISM II trial evaluated DM/Q as PBA treatment in patients with stroke, dementia, or traumatic brain injury.

OBJECTIVE

To report results from the stroke cohort of PRISM II, including the Stroke Impact Scale (SIS).

DESIGN

Open-label trial evaluating twice-daily DM/Q over 90 days.

STUDY PARTICIPANTS

Adults (n = 113) with a clinical diagnosis of PBA secondary to stroke; stable psychiatric medications were allowed.

METHODS

PRISM II was an open-label, 12-week trial enrolling adults with PBA caused by dementia, stroke (reported here), or TBI. All study participants received DM/Q 20/10 mg twice daily. Study visits occurred at baseline and at days 30 and 90.

SETTING

150 U.S. centers.

MAIN OUTCOME MEASUREMENTS

Primary efficacy measure was changed from baseline to day 90 in Center for Neurologic Study-Lability Scale (CNS-LS) scores. Secondary outcomes included PBA episodes (estimated over 7 days), Clinical and Patient/Caregiver Global Impression of Change (CGI-C and PGI-C), Quality of Life-Visual Analog Scale (QOL-VAS), SIS, Patient Health Questionnaire (PHQ-9), and Mini-Mental State Examination (MMSE).

RESULTS

Compared with baseline, CNS-LS scores (SD) improved by -6.2 (6.1, P < .001) at day 30 and -7.6 (6.7, P < .001) at day 90. PBA episodes were reduced by 65% and 75% at day 30 and 90, respectively. Seventy-five percent of clinicians and 67% of patients/caregivers rated PBA as "much" or "very much improved." All SIS items significantly improved from baseline (P < .05, all). Adverse events included diarrhea (4.4%), headache (3.5%), constipation (2.7%), and dizziness (2.7%); 5.3% had adverse events leading to study discontinuation.

CONCLUSIONS

DM/Q effectively treated PBA and was associated with global and functional improvement; adverse events were consistent with the known safety profile of DM/Q.

Enhanced Bulbar Function in Amyotrophic Lateral Sclerosis: The Nuedexta Treatment Trial

The goal of this randomized, blinded, crossover clinical trial was to determine whether Nuedexta (dextromethorphan and quinidine) enhanced speech, swallowing, and salivation in patients with ALS. Sixty patients with amyotrophic lateral sclerosis (ALS) received either Nuedexta or placebo for 28 to 30 days, followed by a 10 to 15-day washout period. Subsequently, patients were switched to the opposite treatment arm for the remaining days of the trial. The primary endpoint was a reduction in the self-report Center for Neurologic Study Bulbar Function Scale (CNS-BFS) score. The rater-administered ALS Functional Rating Scale Revised was the principal secondary endpoint. The CNS-BFS score improved with active treatment, decreasing from a mean of 59.3 in the placebo arm of the trial to 53.5 during the drug-treatment arm (p < 0.001). Each of the individual domains of bulbar function interrogated by the CNS-BFS responded to treatment with Nuedexta as follows: salivation: 15.8 versus 14.3 (p = 0.004); speech: 24.6 versus 22.2 (p = 0.003); swallowing: 18.9 versus 17.1 (p = 0.009). Similarly, the bulbar component of the ALS Functional Rating Scale Revised improved with active treatment (p = 0.003), although the drug did not affect the motor and respiratory components of this scale. This study is unique for several reasons. Firstly, it was driven by patient reports of improved speech and swallowing while taking Nuedexta for control of emotional lability. Secondly, the study was conducted over a short duration (70 days), and thirdly, a self-report scale was selected as the principle outcome measure. Considering the importance of bulbar functions, these results, if confirmed, point to an additional use of Nuedexta as an adjunct to the management of ALS.

Use of Compounded Dextromethorphan-Quinidine Suspension for Pseudobulbar Affect in Hospice Patients

BACKGROUND

Pseudobulbar affect (PBA) consists of unprovoked and uncontrollable episodes of laughing and/or crying. In end-of-life situations, PBA symptoms can be especially distressing to family and friends during an already heightened emotional time. Although a commercial product combining dextromethorphan and quinidine (DMQ) is FDA approved for use in PBA, many hospice patients are unable to swallow any solids or semisolids. An alternative formulation for these patients is needed.

OBJECTIVE

We present here two cases in which we used a compounded DMQ suspension successfully to treat PBA symptoms in the weeks before the patients' death.

DESIGN

A retrospective chart review was completed on the two cases where the DMQ suspension was used. A description of the DMQ suspension formula is described.

SETTING/SUBJECTS

Both patients were under the care of a hospice program; one in home care and one in a skilled nursing facility.

MEASUREMENTS

Episodes of PBA symptoms were summarized in a narrative of the patients' symptom relief.

RESULTS

Both patients tolerated the administration of the DMQ suspension and there were noted improvements in PBA symptoms.

CONCLUSIONS

DMQ suspension is an effective alternative for PBA symptoms in patients who cannot swallow oral solid medication.

An open-label study to assess safety, tolerability, and effectiveness of dextromethorphan/quinidine for pseudobulbar affect in dementia: PRISM II results

BACKGROUND

Dextromethorphan (DM)/quinidine (Q) is an approved treatment for pseudobulbar affect (PBA) based on trials in amyotrophic lateral sclerosis or multiple sclerosis. PRISM II evaluated DM/Q effectiveness and tolerability for PBA secondary to dementia, stroke, or traumatic brain injury; dementia cohort results are reported.

METHODS

This was an open-label, multicenter, 90 day trial; patients received DM/Q 20/10 mg twice daily. Primary outcome was change in Center for Neurologic Study-Lability Scale (CNS-LS) score. Secondary outcomes included PBA episode count and Clinical and Patient/Caregiver Global Impression of Change scores with respect to PBA (CGI-C/PGI-C).

RESULTS

134 patients were treated. CNS-LS improved by a mean (SD) of 7.2 (6.0) points at Day 90/Endpoint (P<.001) vs. baseline. PBA episodes were reduced 67.7% (P<.001) vs. baseline; global measures showed 77.5% CGI-C and 76.5% PGI-C "much"/"very much" improved. Adverse events included headache (7.5%), urinary tract infection (4.5%), and diarrhea (3.7%); few patients dropped out for adverse events (10.4%).

CONCLUSIONS

DM/Q significantly reduced PBA symptoms in patients with dementia; reported adverse events were consistent with the known safety profile of DM/Q. Trial Registration clinicaltrials.gov identifier: NCT01799941.

PRISM II: an open-label study to assess effectiveness of dextromethorphan/quinidine for pseudobulbar affect in patients with dementia, stroke or traumatic brain injury

Background

Phase 3 trials supporting dextromethorphan/quinidine (DM/Q) use as a treatment for pseudobulbar affect (PBA) were conducted in patients with amyotrophic lateral sclerosis (ALS) or multiple sclerosis (MS). The PRISM II study provides additional DM/Q experience with PBA secondary to dementia, stroke, or traumatic brain injury (TBI).

Methods

Participants in this open-label, multicenter, 90-day trial received DM/Q 20/10 mg twice daily. The primary outcome was the Center for Neurologic Study-Lability Scale (CNS-LS), assessing change in PBA episode frequency and severity. The CNS-LS final visit score was compared to baseline (primary analysis) and to the response in a previously conducted placebo-controlled trial with DM/Q in patients with ALS or MS. Secondary outcomes included change in PBA episode count and Clinical Global Impression of Change with respect to PBA as rated by a clinician (CGI-C) and by the patient or caregiver (PGI-C).

Results

The study enrolled 367 participants with PBA secondary to dementia, stroke, or TBI. Mean (standard deviation [SD]) CNS-LS score improved significantly from 20.4 (4.4) at baseline to 12.8 (5.0) at Day 90/Final Visit (change, −7.7 [6.1]; P < .001, 95 % CI: −8.4, −7.0). This magnitude of improvement was consistent with DM/Q improvement in the earlier phase-3, placebo-controlled trial (mean [95 % CI] change from baseline, −8.2 [−9.4, −7.0]) and numerically exceeds the improvement seen with placebo in that study (−5.7 [−6.8, −4.7]). Reduction in PBA episode count was 72.3 % at Day 90/Final Visit compared with baseline (P < .001). Scores on CGI-C and PGI-C showed that 76.6 and 72.4 % of participants, respectively, were “much” or ”very much” improved with respect to PBA. The most frequently occurring adverse events (AEs) were diarrhea (5.4 %), headache (4.1 %), urinary tract infection (2.7 %), and dizziness (2.5 %); 9.8 % had AEs that led to discontinuation. Serious AEs were reported in 6.3 %; however, none were considered treatment related.

Conclusions

DM/Q was shown to be an effective and well-tolerated treatment for PBA secondary to dementia, stroke, or TBI. The magnitude of PBA improvement was similar to that reported in patients with PBA secondary to ALS or MS, and the adverse event profile was consistent with the known safety profile of DM/Q.

Trial registration

Clinicaltrials.gov, NCT01799941, registered on 25 February 2013

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-016-0609-0) contains supplementary material, which is available to authorized users.

Cutaneous Adverse Effects of Neurologic Medications

Life-threatening and benign drug reactions occur frequently in the skin, affecting 8 % of the general population and 2-3 % of all hospitalized patients, emphasizing the need for physicians to effectively recognize and manage patients with drug-induced eruptions. Neurologic medications represent a vast array of drug classes with cutaneous side effects. Approximately 7 % of the United States (US) adult population is affected by adult-onset neurological disorders, reflecting a large number of patients on neurologic drug therapies. This review elucidates the cutaneous reactions associated with medications approved by the US Food and Drug Administration (FDA) to treat the following neurologic pathologies: Alzheimer disease, amyotrophic lateral sclerosis, epilepsy, Huntington disease, migraine, multiple sclerosis, Parkinson disease, and pseudobulbar affect. A search of the literature was performed using the specific FDA-approved drug or drug classes in combination with the terms 'dermatologic,' 'cutaneous,' 'skin,' or 'rash.' Both PubMed and the Cochrane Database of Systematic Reviews were utilized, with side effects ranging from those cited in randomized controlled trials to case reports. It behooves neurologists, dermatologists, and primary care physicians to be aware of the recorded cutaneous adverse reactions and their severity for proper management and potential need to withdraw the offending medication.

Dextromethorphan: An update on its utility for neurological and neuropsychiatric disorders

Dextromethorphan (DM) is a commonly used antitussive and is currently the only FDA-approved pharmaceutical treatment for pseudobulbar affect. Its safety profile and diverse pharmacologic actions in the central nervous system have stimulated new interest for repurposing it. Numerous preclinical investigations and many open-label or blinded clinical studies have demonstrated its beneficial effects across a variety of neurological and psychiatric disorders. However, the optimal dose and safety of chronic dosing are not fully known. This review summarizes the preclinical and clinical effects of DM and its putative mechanisms of action, focusing on depression, stroke, traumatic brain injury, seizure, pain, methotrexate neurotoxicity, Parkinson's disease and autism. Moreover, we offer suggestions for future research with DM to advance the treatment for these and other neurological and psychiatric disorders.