Dextromethorphan: a review of N-methyl-d-aspartate receptor antagonist in the management of pain

Intrathecal methotrexate, central nervous system toxicity, and response to N-methyl-D-aspartate antagonism: An adult case series

Background

Methotrexate (MTX) is administered for the treatment of central nervous system (CNS) hematologic cancers, prophylaxis of CNS dissemination of certain hematological cancers, and in solid tumor leptomeningeal disease. MTX treatment can be limited by CNS toxicity. Dextromethorphan is used to treat MTX neurotoxicity, with most data derived from pediatric case series. In this report, we profile 4 adult patients who developed intrathecal (IT) MTX neurotoxicity to better characterize their response to dextromethorphan treatment.

Methods

A case series of 4 patients who developed neurologic symptoms attributed to IT MTX neurotoxicity subsequently treated with dextromethorphan was devised. Demographic data, clinical characteristics, electroencephalography results, magnetic resonance imaging, cerebrospinal fluid (CSF) characteristics, and dextromethorphan treatment outcomes were described.

Results

Of the 4 patients developing MTX neurotoxicity, neurologic symptoms developed over a timeframe of 2 to 14 days from the precedent MTX exposure. Radiologic phenotypes included subcortical white matter diffusion-restricting lesions, bi-hemispheric subcortical white matter T2-FLAIR hyperintensities, as well as other findings described in the report. Time elapsed from initiation of dextromethorphan to neurologic symptom resolution ranged from 1 to 2 days.

Conclusions

The profiles of 4 adult patients developing suspected IT MTX neurotoxicity syndromes with subsequent response to Dextromethorphan add further data to guide the management of such patients.

Dextromethorphan-Bupropion for the Treatment of Depression: A Systematic Review of Efficacy and Safety in Clinical Trials

BACKGROUND

A significant proportion of adults with major depressive disorder (MDD) do not respond to treatments which are currently used in clinical practice such as first-generation monoamine-based antidepressants.

OBJECTIVES

The objective of this systematic review was to assess the efficacy, safety, and mechanisms of action of AXS-05, a combination of the NMDA-receptor antagonist dextromethorphan with bupropion, in adults with MDD.

METHODS

We searched PubMed, Embase, Google Scholar, and ClinicalTrials.gov for current studies reporting on efficacy and/or safety of AXS-05 in patients with MDD. The search terms included: "AXS-05" OR "dextromethorphan and bupropion" AND "depression". Studies from database inception to January 2023 were evaluated. Risk of bias was assessed using the Cochrane Risk of Bias tool.

RESULTS

The search yielded 54 studies of which 5 were included. All studies had low risk of bias. Depression severity, measured with the Montgomery-Åsberg Depression Rating Scale (MADRS) significantly decreased as early as 1-week post-treatment from baseline when compared to a placebo-controlled group (LS mean difference 2.2; 95% CI 0.6-3.9; p = 0.007) and at 2 weeks compared to an active control group (LS mean difference 4.7; 95% CI 0.6-8.8; p = 0.024). Treatment efficacy could be maintained for up to 12 months with mean MADRS score reduction of 23 points from baseline. Clinical remission and response rates also improved at week 1 and were maintained for 12 months. The treatment was well-tolerated, with some transient adverse events reported.

CONCLUSION

Current evidence suggests that the combination of dextromethorphan and bupropion is a well-tolerated, rapid-acting treatment option for adults with MDD. Initial success with AXS-05 supports the mechanistic role of glutamatergeric and sigma 1 signaling in the pathophysiology of MDD.

Interventional Mental Health: A Transdisciplinary Approach to Novel Psychiatric Care Delivery

Mental health disorders are among the most common health conditions in the United States. Traditional clinical treatments rely on psychiatric counseling and, in many cases, prescription medications. We propose an innovative model, Interventional Mental Health, which employs a combination of modalities through a multifaceted approach to treat conditions that have exhibited limited responsiveness to traditional methods and individuals afflicted with multiple comorbidities simultaneously. We hypothesize that creating a unique treatment algorithm combining current therapeutic modalities such as Stellate Ganglion Blocks (SGB), Transcranial Magnetic Stimulation (TMS) therapy, and ketamine therapy, within a consolidated timeframe, will yield synergistic outcomes among patients presenting with comorbid post-traumatic stress disorder (PTSD), depression, and/or anxiety.

A double-blinded, placebo-controlled, randomized study to evaluate the efficacy of perioperative dextromethorphan compared to placebo for the treatment of postoperative pain: a study protocol

Background

Pain management is a critical component of comprehensive postsurgical care, as it influences patient safety and outcomes, and inadequate control has been associated with the development of chronic pain syndromes. Despite recent improvements, the management of postoperative pain following total knee arthroplasty (TKA) remains a challenge. The use of opioid-sparing, multimodal analgesic regimens has broad support, but there is a paucity of high-quality evidence regarding optimal postoperative protocols and novel approaches are needed. Dextromethorphan stands out among both well-studied and emerging pharmacological adjuncts for postoperative pain due its robust safety profile and unique pharmacology. The purpose of this study is to evaluate the efficacy of multi-dose dextromethorphan for postoperative pain control following TKA.

Methods

This is a single-center, multi-dose, randomized, double-blinded, placebo-controlled trial. A total of 160 participants will be randomized 1:1 to receive either 60 mg oral dextromethorphan hydrobromide preoperatively, as well as 30 mg 8 h and 16 h postoperatively, or matching placebo. Outcome data will be obtained at baseline, during the first 48 h, and the first two follow-up visits. The primary outcome measure will be total opioid consumption at 24 h postoperatively. Secondary outcomes related to pain, function, and quality of life will be evaluated using standard pain scales, the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS, JR) questionnaire, the Patient-Reported Outcomes Measurement Information System (PROMIS-29) questionnaire, and clinical anchors.

Discussion

This study has a number of strengths including adequate power, a randomized controlled design, and an evidence-based dosing schedule. As such, it will provide the most robust evidence to date on dextromethorphan utilization for postoperative pain control following TKA. Limitations include not obtaining serum samples for pharmacokinetic analysis and the single-center study design.

Trial registration

This trial has been registered on the National Institute of Health’s ClinicalTrials.gov (NCT number: NCT05278494). Registered on March 14, 2022.

Duloxetine for Postoperative Pain Control Following Knee or Hip Replacement: A Systematic Review and Meta-Analysis

Background

Duloxetine is a Food and Drug Administration-approved selective norepinephrine reuptake inhibitor for treating depression, anxiety, fibromyalgia, and neuropathic and chronic musculoskeletal pain. This meta-analysis aims to evaluate the efficacy of duloxetine in reducing pain and postoperative opioid use following lower extremity total joint arthroplasty.

Methods

A literature search was performed, identifying randomized controlled trials investigating duloxetine for pain management after total hip and total knee arthroplasty. Data from the visual analog scale (VAS) for pain during movement and at rest were extracted for postoperative days (PODs) 1, 3, 7, and 14, as well as postoperative week 6 and postoperative month 3. Opioid use data were obtained at 24, 48 and 72 hours. All data were analyzed using inverse variance with random effects and presented as weighted mean difference.

Results

Eight unique studies were identified and included, 7 of which were analyzed quantitatively. Duloxetine decreased postoperative opioid consumption at 48 and 72 hours. For VAS for pain at rest, significantly reduced pain was reported by duloxetine-treated patients at POD 3, POD 7, and postoperative week 6. For VAS for pain at movement, significantly reduced pain was reported by duloxetine-treated patients at POD1, POD 3, POD 7, POD 14, postoperative week 6, and postoperative month 3.

Conclusions

Duloxetine appears to decrease postoperative pain and opioid consumption following total joint arthroplasty. However, definitive conclusions are limited by small sample size and study heterogeneity. While there is a need for follow-up studies to determine the optimal dose, duration, and patient population, strong preliminary data provide robust support for future large-scale efficacy studies.

Dextromethorphan premedication in the alleviation of cough during flexible bronchoscopy in adults: A randomized double-blind placebo-controlled trial

BACKGROUND AND OBJECTIVE

Cough is invariably encountered during flexible bronchoscopy despite sedation and topical anaesthetics. The ideal cough suppressant during flexible bronchoscopy is not known. We assessed the role of dextromethorphan premedication in relieving the cough during flexible bronchoscopy in adults.

METHODS

In this single-centre study, we randomized patients aged ≥18 years to receive dextromethorphan syrup 30 ml (90 mg) or an equal volume of placebo 1 h before the procedure. Patients rated their cough severity and discomfort on a visual analogue scale at the end of the procedure. Bronchoscopists also rated cough severity at the end of the procedure.

RESULTS

Out of 112 patients screened, 94 patients (median (interquartile range [IQR]) age 51 (36.25-60.75) years, male: female 2.13:1) were randomized to either the dextromethorphan (n = 47) or placebo (n = 47) groups. The patients-rated median (IQR) cough scores at the end of the procedure were 15 (10-23) mm in dextromethorphan versus 20 (12-45.5) mm in placebo groups (p = 0.03). Patients-rated median cough scores at 1 h (5 mm vs. 6 mm, p = 0.21), discomfort scores (12.5 mm vs. 12.5 mm, p = 0.49), and midazolam and lignocaine usage were similar between the two groups. The bronchoscopist-rated median cough score was non-significantly lower in the intervention compared to the placebo (26 mm vs. 35 mm, p = 0.09) groups.

CONCLUSION

Dextromethorphan premedication 1 h before flexible bronchoscopy may have an additive effect on cough suppression under conscious sedation and topical lignocaine. Further trials are needed to reiterate our findings with certainty.

Antipsychotic Drugs Efficacy in Dextromethorphan-Induced Psychosis

Psychosis is known as a broad term of symptoms that cause serious disorganization of behavior, thinking, and perception of reality. One of the medicines that recently gained much attention in terms of its psychotic potential is dextromethorphan (DXM). DXM, a widely used antitussive drug, is a commonly abused drug because of its euphoric, hallucinogenic, and dissociative properties. To date, DXM is a legally marketed cough suppressant that is neither a controlled substance nor a regulated chemical under the Controlled Substances Act. The management of DXM-related psychosis is dependent on the type of psychotic symptoms. Atypical neuroleptics (i.e., olanzapine, risperidone, quetiapine) and typical haloperidol have been used in symptomatic treatment due to their efficacy, especially in positive symptoms (hallucinations and delusions). These agents are also recognized as the preferred option in the symptomatic treatment of DXM-related psychosis due to their better efficacy and safety profile than typical haloperidol in the short-term course. The focus of the present review concerns the current stage of knowledge about DXM psychotic potency as well as the management of DXM-related psychoses with a special emphasis on atypical antipsychotic drugs (i.e., olanzapine, risperidone, quetiapine, and haloperidol).

Preliminary Results on the Long-Term Effects of Dextromethorphan on MDMA-Mediated Serotonergic Deficiency and Volumetric Changes in Primates Based on 4-[18F]-ADAM PET/MRI

Alterations to the serotonergic system due to 3,4-methylenedioxymethamphetamine (MDMA) (ecstasy) consumption have been extensively documented. However, knowledge of the reversibility of these neurotoxic effects based on in vivo evaluations of serotonin transport (SERT) availability remains limited. This study aimed to evaluate the long-term neurotoxicity of MDMA after 66 months abstinence and explored whether Dextromethorphan, a non-competitive N-methyl-D-aspartate (NMDA) receptor, could attenuate MDMA-induced neurotoxicity using 4-[18F]-ADAM, an imaging ligand that selectively targets SERT, with positron emission tomography technology (PET). Nine monkeys (Macaca cyclopis) were used in this study: control, MDMA, and DM + MDMA. Static 4-[18F]-ADAM PET was performed at 60 and 66 months after drug treatment. Serotonin transport (SERT) availability was presented as the specific uptake ratios (SURs) of 4-[18F]-ADAM in brain regions. Voxel-based region-specific SERT availability was calculated to generate 3D PET/MR images. Structural Magnetic Resonance Imaging (MRI) volumetric analysis was also conducted at 60 months. Significantly decreased 4-[18F]-ADAM SURs were observed in the striatum and thalamus of the MDMA group at 60 and 66 months compared to controls; the midbrain and frontal cortex SURs were similar at 60 and 66 months in the MDMA and control groups. All eleven brain regions showed significantly lower (∼13%) self-recovery rates over time; the occipital cortex and cingulate recovered to baseline by 66 months. DM attenuated MDMA-induced SERT deficiency on average, by ∼8 and ∼1% at 60 and 66 months, respectively; whereas significant differences were observed between the thalamus and amygdala of the MDMA and DM + MDMA groups at 66 months. Compared to controls, the MDMA group exhibited significantly increased (∼6.6%) gray matter volumes in the frontal cortex, occipital cortex, caudate nucleus, hippocampus, midbrain, and amygdala. Moreover, the gray matter volumes of the occipital cortex, hippocampus and amygdala correlated negatively with the 4-[18F]-ADAM SURs of the same regions. DM (n = 2) did not appear to affect MDMA-induced volumetric changes. The 4-[18F]-ADAM SURs, lower self-recovery rate and increased volumetric values indicate the occipital cortex, hippocampus and amygdala still exhibit MDMA-induced neurotoxicity after 66 months’ abstinence. Moreover, DM may prevent MDMA-induced serotonergic deficiency, as indicated by increased 4-[18F]-ADAM SURs and SERT availability, but not volumetric changes.

Ventral tegmental area serotonin 5-HT1A receptors and corticolimbic cFos/BDNF/GFAP signaling pathways mediate dextromethorphan/morphine anti-allodynia

AIMS

The present study examined the role of ventral tegmental area (VTA) serotonergic 5HT_1A receptors in dextromethorphan/morphine-induced anti-allodynia and the possible changes of corticolimbic cFos, brain-derived neurotrophic factor (BDNF), and glial fibrillary acidic protein (GFAP) following the treatments.

MATERIALS AND METHODS

The VTA cannulation and the chronic constriction of the sciatic nerve were performed in male Wistar rats. Flexion withdrawal thresholds to mechanical stimulation in the hind-limb were determined using von Frey hairs. The expressions of cFos, BDNF, and GFAP were evaluated using the Western blotting technique.

KEY FINDINGS

BDNF (in the hippocampus), and GFAP (in the targeted sites) levels were increased following neuropathic pain. Morphine administration induced an anti-allodynic effect with a decrease in the amygdala BDNF level. Dextromethorphan/morphine-induced anti-allodynia was accompanied by the decrease of hippocampus/amygdala/PFC GFAP and amygdala cFos expressions. The PFC BDNF expression level was increased in dextromethorphan/morphine-treated rats. Intra-VTA microinjection of (S)-WAY100135 (1 µg/rat), a selective 5-HT_1A receptor antagonist, inhibited the anti-allodynic effect of dextromethorphan/morphine. This treatment increased the cFos level in the hippocampus and the amygdala while decreased the PFC level of cFos. The hippocampal BDNF expression was significantly increased, while the amygdala and the PFC expressions of BDNF were decreased under treatment. (S)-WAY100135 plus dextromethorphan/morphine increased the hippocampal/amygdala and PFC levels of GFAP.

SIGNIFICANCE

These findings indicate that dextromethorphan could potentiate the analgesic effect of morphine via the implication of the VTA serotonin 5-HT_1A receptors. It seems that the changes in the corticolimbic cFos/BDNF/GFAP signaling pathway may be involved in the observed anti-allodynic effect.

The Effect of Intrathecal Injection of Dextromethorphan on the Experimental Neuropathic Pain Model

Background

Peripheral glucocorticoid receptors (GRs) are altered by peripheral nerve injury and may modulate the development of neuropathic pain. Two central pathogenic mechanisms underlying neuropathic pain are neuroinflammation and N-methyl-D-aspartate receptor (NMDAR)-dependent neural plasticity in the spinal cord.

Objectives

This study examined the effect of the non-competitive NMDAR antagonist dextromethorphan on partial sciatic nerve ligation (PSL)-induced neuropathic pain and the spinal expression of the glucocorticoid receptor (GR).

Methods

Male mice were randomly assigned into a sham group and two groups receiving PSL followed by intrathecal saline vehicle or dextromethorphan (iDMP). Vehicle or iDMP was administered 8 - 14 days after PSL. The hotplate paw-withdrawal latency was considered to measure thermal pain sensitivity. The spinal cord was then sectioned and immunostained for GR.

Results

Thermal hyperalgesia developed similarly in the vehicle and iDMP groups prior to the injections (P = 0.828 and 0.643); however, it was completely mitigated during the iDMP treatment (P < 0.001). GR expression was significantly higher in the vehicle group (55.64 ± 4.50) than in the other groups (P < 0.001). The iDMP group (9.99 ± 0.66) showed significantly higher GR expression than the sham group (6.30 ± 1.96) (P = 0.043).

Conclusions

The suppression of PLS-induced thermal hyperalgesia by iDMP is associated with the downregulation of GR in the spinal cord, suggesting that this analgesic effect is mediated by inhibiting GR-regulated neuroinflammation.

Safety of the Geneva Cocktail, a Cytochrome P450 and P-Glycoprotein Phenotyping Cocktail, in Healthy Volunteers from Three Different Geographic Origins

INTRODUCTION AND OBJECTIVE: Cytochrome P450 enzymes are the major drug-metabolizing enzymes in humans and the importance of drug transport proteins, in particular P-glycoprotein, in the variability of drug response has also been highlighted. Activity of cytochrome P450 enzymes and P-glycoprotein can vary widely between individuals and genotyping and/or phenotyping can help assess their activity. Several phenotyping cocktails have been developed. The Geneva cocktail is composed of a specific probe for six different cytochrome P450 enzymes and one for P-glycoprotein and was used in the context of a research aiming at exploring genotypes and phenotypes in distinct human populations (NCT02789527). The aim of the present study is to solely report the safety results of the Geneva cocktail in the healthy volunteers of these populations.

MATERIALS AND METHODS

The Geneva cocktail is composed of caffeine, bupropion, flurbiprofen, omeprazole, dextromethorphan, midazolam, and fexofenadine. The volunteers fasted and avoided drinking caffeine-containing beverages or food and grapefruit juice overnight before receiving the cocktail orally. They provided blood spots for the probes' concentrations at 2, 3, and 6 h after ingestion and were asked about adverse events.

RESULTS

A total of 265 healthy adult volunteers were included from Ethiopia, Oman, and the Czech Republic. The mean plasma concentrations at the 2-h sampling time of each probe drug in the total sample were: 1663 ng/mL for caffeine, 8 ng/mL for bupropion, 789 ng/mL for flurbiprofen, 6 ng/mL for dextromethorphan, 2 ng/mL for midazolam, 35 ng/mL for fexofenadine, and 103 ng/mL for omeprazole. Four adverse events were observed representing an occurrence of 1.5%. All these events were categorized as mild to moderate, non-serious, and resolved spontaneously. A causal link with the cocktail cannot be excluded because of the temporal relationship but is at most evaluated as possible according to the World Health Organization-Uppsala Monitoring Centre causal assessment system.

CONCLUSIONS

In this research, healthy volunteers from three different human populations were phenotyped with the Geneva cocktail. Four adverse events were observed, confirming the safety of this cocktail that is given at lower than clinically relevant doses and therefore results in concentrations lower than those reported to cause adverse events.

Inhibition of the ERK1/2 Phosphorylation by Dextromethorphan Protects against Core Autistic Symptoms in VPA Induced Autistic Rats: In Silico and in Vivo Drug Repurposition Study

The imbalance between excitatory and inhibitory neurotransmitters is explicitly related to the pathophysiology of autism spectrum disorder (ASD). The role of an NMDA receptor antagonist, dextromethorphan, was studied in ameliorating the ASD-like symptoms by regulating the excitatory and inhibitory imbalance using the valproic acid (VPA) model of ASD. Female Wistar rats were administered VPA [600 mg/kg on embryonic day ED-12.5] through intraperitoneal (ip) injection to induce ASD in pups. Autistic pups were then given dextromethorphan (10, 15, and 30 mg/kg; ip) and risperidone (2.5 mg/kg; ip) from PND 23 to 43 in different groups. Behavioral tests (three chamber sociability, self-grooming, Morris water maze, elevated plus maze, open field, rotarod, grip strength), oxidative stress and inflammatory markers, histological evaluation (H&E, Nissil staining), and NMDA and ERK1/2 expression by immunohistochemistry and RT-PCR were done. The in silico modeling of dextromethorphan against PPDA, TCN-201, MK-22, EVT-101 on NMDA receptors was also performed. Dextromethorphan (30 mg/kg) rescued the impaired behavioral patterns including social excitability, hyperactivity, repetitive and restricted behaviors as well as mitigation of the memory and motor coordination. The levels of various oxidative stress markers (GSH, SOD, catalase, MDA) and inflammatory markers (IL-1β, IL-6, IL-10, TNF-α) were ameliorated by different doses of dextromethorphan. It also reduced the neuronal injury score and rescued the overly expressed pERK1/2 and NMDA signaling in both the prefrontal cortex and hippocampus of the autistic pups. In silico results showed favorable binding of dextromethorphan against TCN-201 and MK-22 binding sites. The present study provided experimental evidence for the potential therapeutic role of dextromethorphan in attenuating autism symptomatology in the ASD model of rats. Thus, modulation of the glutamatergic signaling can be a potential target for ASD treatment.

Comparative Evaluation of Preemptive Analgesia of Dextromethorphan and Ibuprofen in Third Molar Surgeries

Introduction:

Postoperative pain following third molar removal is one of the most common and unpleasant complications encountered in routine surgical practice. Various methods have been advocated to minimize the postoperative pain: preemptive analgesia is one of those found to be effective.

Objective:

The aim of this study was to compare the preemptive analgesic efficacy of Dextromethorphan (DM) and Ibuprofen in the third molar surgeries.

Material and Methods:

Thirty-six patients reporting to our institution were included in the study. Patients were randomized into three groups of 12 patients each to receive either DM 30 mg, ibuprofen 100 mg, or placebo in the form of multivitamin syrup, 90 min before the procedure. The difficulty of removal of the teeth was assessed using Campbell difficulty score. The study objectives were to evaluate the time elapsed since surgery after which the patient took their first dose of aceclofenac, to evaluate the postoperative pain using visual analog scale score, and to record the number of aceclofenac tablets consumed postoperatively.

Results:

The results of the study revealed that preemptive DM was significantly better than ibuprofen and placebo in the duration of time that elapsed before the patients consumed their first analgesic postoperatively. Preemptive DM also reduced the total number of aceclofenac tablets consumed on the day of surgery and on the 1^st postoperative day, but the difference was not statistically significant. Between the two drugs, DM is better suited for providing preemptive analgesia. No side effects at a dose of 30 mg of DM were noted in any of the patients.

Conclusion:

DM premedication is a viable preemptive analgesic in reducing postoperative pain.

Effect of dextromethorphan/quinidine on pentylenetetrazole- induced clonic and tonic seizure thresholds in mice

INTRODUCTION

This study aimed to investigate the effects of dextromethorphan (DM) or dextromethorphan/quinidine (DM/Q) against pentylenetetrazole (PTZ)- induced seizure threshold in mice and the probable involvement of N-methyl d-aspartate (NMDA), sigma-1 and serotonin 1A (5-HT_1A) receptors.

MATERIAL AND METHODS

NMRI male mice (25-30 g) received quinidine (10, 20, and 30 mg/kg), DM (5, 10, 25, and 50 mg/kg) or DM/Q (10/20, 25/20, and 50/20 mg/kg), 30 min before the infusion of PTZ. ketamine (1 and 5 mg/kg), BD-1047 (2.5 and 5 mg/kg) or WAY-100635 (0.5 and 1 mg/kg) were administrated as pre-treatment 30 min before the selected dose of DM/Q. Seizures were induced by intravenous PTZ infusion. All data were presented as means ± S.E.M. One-way ANOVA test was used to determine statistical significance (p < 0.05).

RESULTS

DM (25 and 50 mg/kg) significantly increased PTZ- induced seizure threshold. DM/Q at doses of 10/20 and 25/20 mg/kg had anticonvulsant effect, while at a dose of 50/20 mg/kg attenuated anticonvulsant effect of DM 50 mg/kg. Ketamine (5 mg/kg) or WAY-100635 (1 mg/kg) potentiated, while BD-1047 (2.5 and 5 mg/kg) attenuated the anticonvulsant effect of DM/Q 10/20 mg/kg.

CONCLUSION

The results of present study demonstrate that combination with quinidine potentiates the anticonvulsant effect of DM at lower doses, while attenuates it at higher dose. Meanwhile, the effects of DM/Q on seizure activity likely involve an interaction with NMDA, the sigma-1 or the 5-HT_1A receptor which may be secondary to the elevation of DM levels.

Expanding Role of NMDA Receptor Antagonists in the Management of Pain

Pain management is complex regardless of whether the pain is acute or chronic in nature or non-cancer or cancer related. In addition, relatively few pain pharmacotherapy options with adequate efficacy and safety data currently exist. Consequently, interest in the role of NMDA receptor antagonists as a pharmacological pain management strategy has surfaced. This narrative review provides an overview of the NMDA receptor and elaborates on the pharmacotherapeutic profile and pain management literature findings for the following NMDA receptor antagonists: ketamine, memantine, dextromethorphan, and magnesium. The literature on this topic is characterized by small studies, many of which exhibit methodological flaws. To date, ketamine is the most studied NMDA receptor antagonist for both acute and chronic pain management. Although further research about NMDA receptor antagonists for analgesia is needed and the optimal dosage/administration regimens for these drugs have yet to be determined, ketamine appears to hold the most promise and may be of particular value in the perioperative pain management realm.

Semi-quantitative analysis of tramadol, dextromethorphan, and metabolites in decomposed skeletal tissues by ultra performance liquid chromatography quadrupole time of flight mass spectrometry

The use of filtration/pass-through extraction (FPTE) and ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-qTOF-MS) to detect tramadol (TRAM), dextromethorphan (DXM), and metabolites from skeletal remains is described. Rats (n=5) received 50 mg/kg tramadol and were euthanized by CO₂ asphyxiation approximately 30 minutes post-dose. Rats (n=4) received 75 mg/kg dextromethorphan and were euthanized by CO₂ asphyxiation approximately 45 minutes post-dose. Remains decomposed to skeleton outdoors and vertebral bones were collected. Bones were cleaned, dried, and pulverized to a fine powder. Bones underwent dynamic methanolic extraction followed by FPTE before analysis using UPLC-qTOF-MS. Recovery was at least 90% of maximal value within the first 10 minutes of methanolic extraction for all samples assayed. Analytical response was measured over the concentration range of 1-500 ng/mL, with precision and bias <20% in triplicate analyses of all calibrators, and a limit of detection of 1 ng/mL for TRAM, DXM, and all metabolites. The vertebral bone analyzed using this method detected TRAM, DXM, and their respective metabolites in all samples analyzed.

NMDAR antagonists for the treatment of diabetes mellitus-Current status and future directions

Diabetes mellitus is characterized by chronically elevated blood glucose levels accelerated by a progressive decline of insulin-producing β-cells in the pancreatic islets. Although medications are available to transiently adjust blood glucose to normal levels, the effects of current drugs are limited when it comes to preservation of a critical mass of functional β-cells to sustainably maintain normoglycemia. In this review, we recapitulate recent evidence on the role of pancreatic N-methyl-D-aspartate receptors (NMDARs) in β-cell physiology, and summarize effects of morphinan-based NMDAR antagonists that are beneficial for insulin secretion, glucose tolerance and islet cell survival. We further discuss NMDAR-mediated molecular pathways relevant for neuronal cell survival, which may also be important for the preservation of β-cell function and mass. Finally, we summarize the literature for evidence on the role of NMDARs in the development of diabetic long-term complications, and highlight beneficial pharmacologic aspects of NMDAR antagonists in diabetic nephropathy, retinopathy as well as neuropathy.

Modulation of NMDA Receptor Activity in Fibromyalgia

Activation of the N-methyl-d-aspartate receptor (NMDAR) results in increased sensitivity of spinal cord and brain pathways that process sensory information, particularly those which relate to pain. The NMDAR shows increased activity in fibromyalgia and hence modulation of the NMDAR is a target for therapeutic intervention. A literature review of interventions impacting on the NMDAR shows a number of drugs to be active on the NMDAR mechanism in fibromyalgia patients, with variable clinical effects. Low-dose intravenous ketamine and oral memantine both show clinically useful benefit in fibromyalgia. However, consideration of side-effects, logistics and cost need to be factored into management decisions regarding use of these drugs in this clinical setting. Overall benefits with current NMDAR antagonists appear modest and there is a need for better strategy trials to clarify optimal dose schedules and to delineate potential longer–term adverse events. Further investigation of the role of the NMDAR in fibromyalgia and the effect of other molecules that modulate this receptor appear important to enhance treatment targets in fibromyalgia.

A Stroke Mimic: Methotrexate-induced Neurotoxicity in the Emergency Department

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most common form of childhood leukemia. The treatment of ALL involves multimodality therapy, and methotrexate (MTX) remains a mainstay of treatment. A complication of MTX therapy includes acute, subacute, and chronic neurotoxocity. Signs and symptoms may range from headaches, dizziness, and mood disorders to seizures and stroke-like symptoms.

CASE REPORT

An 18-year-old woman with a history of ALL presented to the emergency department with acute onset of right-sided facial paralysis, right upper extremity flaccid paralysis, and right lower extremity weakness after receiving MTX therapy 3 days earlier. Diagnostic studies were unremarkable and the patient was treated with oral dextromethorphan for presumed MTX-induced neurotoxicity. The patient's symptoms began to improve within hours and she was discharged home within 48 hours with no neurologic deficits. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Emergency physicians should be aware of this complication of MTX therapy given the sensitivity in regards to time with respect to cerebral vascular accidents. An awareness of this complication in the setting of the appropriate history and physical examination can lead to an accurate diagnosis and intervention and the avoidance of administering thrombolytics.

Clinical applications of hallucinogens: A review

Hallucinogens fall into several different classes, as broadly defined by pharmacological mechanism of action, and chemical structure. These include psychedelics, entactogens, dissociatives, and other atypical hallucinogens. Although these classes do not share a common primary mechanism of action, they do exhibit important similarities in their ability to occasion temporary but profound alterations of consciousness, involving acute changes in somatic, perceptual, cognitive, and affective processes. Such effects likely contribute to their recreational use. However, a growing body of evidence indicates that these drugs may have therapeutic applications beyond their potential for abuse. This review will present data on several classes of hallucinogens with a particular focus on psychedelics, entactogens, and dissociatives, for which clinical utility has been most extensively documented. Information on each class is presented in turn, tracing relevant historical insights, highlighting similarities and differences between the classes from the molecular to the behavioral level, and presenting the most up-to-date information on clinically oriented research with these substances, with important ramifications for their potential therapeutic value. (PsycINFO Database Record

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.

Medication Repurposing in Pediatric Patients: Teaching Old Drugs New Tricks

OBJECTIVES

Gaps in pediatric therapeutics often result in off-label use and specifically, novel uses for existing medications, termed "drug repurposing." Drug Information (DI) queries to a Pediatric Medication Resource Center of a large metropolitan pediatric hospital in New York and inherent difficulties in retrieving evidence-based information prompted a review of current medication repurposing for pediatric patients. The objective included characterization of innovative off-label use of medications Food and Drug Administration (FDA)-approved for 1 or more indications to treat a totally different disorder or indication in pediatric patients.

METHODS

A systematic literature review was conducted to retrieve publications describing repurposed medications in pediatric patients. Excluded was FDA-approved indications used off-label in pediatric patients (e.g., different dose), preclinical data, adult use only, and experimental use. Evidence quality was classified using a modified American Academy of Neurology Level of Evidence. Results were analyzed using χ(2) at p < 0.05.

RESULTS

Over 2000 references were retrieved and reviewed. A total of 101 medications repurposed for novel off-label uses for pediatric patients were identified: 38 for neonates, 74 for children, and 52 for adolescents. Neonates and infants were least likely to receive a medication for a repurposed use. Strong or intermediate evidence existed in 80.2% of cases. The evidence was weak in 19.8%. No significant relationship was observed between the pediatric age group and strength of the literature. Most repurposed uses pertained to generic or widely used medications. Less than 5% of medications were first marketed after 2011.

CONCLUSIONS

While not exhaustive, the present study represents the most comprehensive listing of novel uses exclusive to pediatric patients. Further research is needed to identify the frequency of repurposed uses. The valuable DI role of pharmacists in assessing repurposed uses is of expanding and increasing importance to ensure such uses are evidence-based.

Evaluation of the role of N-methyl-D-aspartate (NMDA) receptors in insulin secreting beta-cells

The possibility that antagonism of N-methyl-D-aspartate (NMDA) receptors represent a novel drug target for diabetes prompted the current studies probing NMDA receptor function in the detrimental actions of homocysteine on pancreatic beta-cell function. Cellular insulin content and release, changes in membrane potential and intracellular Ca(2+) and gene expression were assessed following acute (20min) and long-term (18h) exposure of pancreatic clonal BRIN-BD11 beta-cells to known NMDA receptor modulators in the absence and presence of cytotoxic concentrations of homocysteine. As expected, acute or long-term exposure to homocysteine significantly suppressed basal and secretagogue-induced insulin release. In addition, NMDA reduced glucose-stimulated insulin secretion (GSIS). Interestingly, the selective NMDA receptor antagonist, MK-801, had no negative effects on GSIS. The effects of the NMDA receptor modulators were largely independent of effects on membrane depolarisation and increases of intracellular Ca(2+). However, combined culture of the NMDA antagonist, MK-801, with homocysteine did enhance intracellular Ca(2+) levels. Actions of NMDA agonists/antagonists and homocysteine on signal transduction pathways were independent of changes in cellular insulin content, cell viability, DNA damage or expression of key beta-cell genes. Taken together, the data support a role for NMDA receptors in controlling pancreatic beta-cell function. However, modulation of NMDA receptor function was unable to prevent the detrimental beta-cell effects of homocysteine.

Neuronal Dysregulation in Stroke-Associated Pseudobulbar Affect (PBA): Diagnostic Scales and Current Treatment Options

Until recently there was little understanding of the exact pathophysiology and treatment choices for stroke patients with Pseudobulbar affect (PBA). PBA is typically characterized by outbursts or uncontrollable laughing or crying and in the majority of patients, the outbursts being involuntary and incompatible with the patients' emotional state. PBA is a behavioral syndrome reported to be displayed in 28-52% of stroke patients with first or multiple strokes, and incidence may be higher in patients who have had prior stroke events, and higher in females. There is typically involvement of glutaminergic, serotoninergic and dopaminergic neuronal circuits of the corticolimbic-subcorticothalamic-pontocerebellar network. PBA is now understood to be a disinhibition syndrome in which specific pathways involving serotonin and glutamate are disrupted or modulated causing reduced cortical inhibition of a cerebellar/brainstem-situated "emotional" laughing or crying focal center. Stroke-induced disruption of one or more neuronal pathway circuits may "disinhibit" voluntary laughing and crying making the process involuntary. With a "new" treatment currently being marketed to treat PBA patients, this article will delve into the neurological and physiological basis for PBA in stroke, and review progress with the diagnosis and treatment of PBA.

Modifying chemotherapeutic management of a patient with Burkitt's lymphoma and pre-existing motor neurone disease

WHAT IS KNOWN AND OBJECTIVE

Intensive chemotherapy for treatment of Burkitt's lymphoma (BL) - a high-grade lymphoproliferative disorder (LPD) - can cause neurotoxicity. An association between motor neurone disease (MND) and LPDs has previously been described, but there is a lack of recommendations available to guide management of such patients. This report aims to describe suitable management of BL in a patient with MND.

CASE DESCRIPTION

A 66-year-old woman with a history of MND affecting her limbs was diagnosed with bulky, extranodal, high-risk gastric BL. Standard chemotherapy is with multiple non-cross-resistant cytotoxic agents. To avoid exacerbation of neuropathy, six cycles of a modified regimen was planned, aiming to minimize exposure to the most neurotoxic agents. A PET-FDG-negative remission was obtained at 12 months, without the signs of central neurotoxicity, peripheral neuropathy or muscle weakness.

WHAT IS NEW AND CONCLUSION

High-intensity chemotherapy, minimizing known neurotoxic agents, was delivered safely and effectively in a patient with BL and pre-existing MND. More case descriptions are required to guide management decisions.

Intravenous dextromethorphan/quinidine inhibits activity of dura-sensitive spinal trigeminal neurons in rats

BACKGROUND

Migraine is a chronic neurological disorder characterized by episodes of throbbing headaches. Practically all medications currently used in migraine prophylaxis have a number of substantial disadvantages and use limitations. Therefore, the further search for principally new prophylactic antimigraine agents remains an important task. The objective of our study was to evaluate the effects of a fixed combination of dextromethorphan hydrobromide and quinidine sulphate (DM/Q) on activity of the spinal trigeminal neurons in an electrophysiological model of trigemino-durovascular nociception.

METHODS

The study was performed in 15 male Wistar rats, which were anaesthetized with urethane/α-chloralose and paralysed using pipecuronium bromide. The effects of cumulative intravenous infusions of DM/Q (three steps performed 30 min apart, 15/7.5 mg/kg of DM/Q in 0.5 mL of isotonic saline per step) on ongoing and dural electrical stimulation-induced neuronal activities were tested in a group of eight rats over 90 min. Other seven animals received cumulative infusion of equal volumes of saline and served as control.

RESULTS

Cumulative administration of DM/Q produced steady suppression of both the ongoing activity of the spinal trigeminal neurons and their responses to electrical stimulation of the dura mater.

CONCLUSIONS

It is evident that the observed DM/Q-induced suppression of trigeminal neuron excitability can lead to a reduction in nociceptive transmission from meninges to higher centres of the brain. Since the same mechanism is believed to underlie the pharmacodynamics of many well-known antimigraine drugs, results of the present study enable us to anticipate the potential efficacy of DM/Q in migraine.

A double-blind, placebo-controlled trial of dextromethorphan combined with clonidine in the treatment of heroin withdrawal

Dextromethorphan has been reported to ameliorate opioid withdrawal symptoms in both animal and human subjects. In the present study, we investigated the efficacy of dextromethorphan as an add-on medication in heroin detoxification treatment in a double-blind, placebo-controlled design. Sixty-five heroin-dependent patients (male, 63; female, 2) participated in this inpatient detoxification trial after giving informed consent. Clonidine 0.075 mg 4 times a day was given as an antiwithdrawal medication at baseline. Each patient was then randomly assigned to treatment with either dextromethorphan 60 mg or placebo 4 times a day as additional medication. Flurazepam 30 mg was given before bedtime for insomnia. Other medications that were allowed included loperamide for diarrhea and lorazepam for agitation. Participants were monitored using the Objective Opioid Withdrawal Scale 3 times a day as the primary outcome to compare drug efficacy between groups. Generalized estimating equation model analysis revealed that the Objective Opioid Withdrawal Scale had no group difference between dextromethorphan and placebo group overall (P = 0.29), whereas a significant difference between groups was found during day 3 to day 6 (P = 0.04) by post hoc analysis. There was no difference in the Clinical Global Impression Scale, patient's impression of treatment, and use of ancillary medications between groups. No severe adverse effects were noticed. We suggest that dextromethorphan has some beneficial effect in attenuating the severity of opioid withdrawal symptoms and can be used as an adjunction medication in the treatment of opioid withdrawal, whereas the exact efficacy needs further investigation.

Efficacy of dextromethorphan and cyclosporine a for acute encephalopathy

Acute encephalopathy with biphasic seizures and late reduced diffusion was recently established clinicoradiologically as an encephalopathy syndrome. The outcome of this encephalopathy is characterized by a low mortality rate and high incidence of neurologic sequelae. Although the exact pathogenesis of this encephalopathy is uncertain, excitotoxic injury with delayed neuronal death is proposed. On the basis of this hypothesis, we tried a combination therapy of N-methyl-D-aspartate receptor antagonist, dextromethorphan, and apoptosis inhibitor, cyclosporine A, in four patients with acute encephalopathy with biphasic seizures and late reduced diffusion. All patients recovered except for hyperactivity in one patient. Furthermore, an additional four patients with near-miss encephalopathy, who showed mild disturbance of consciousness at 24 hours after prolonged febrile seizures associated with exanthem subitum, recovered without secondary seizures by the early administration of dextromethorphan. The combination regimen of dextromethorphan and cyclosporine A could be effective for the treatment and prevention of acute encephalopathy with biphasic seizures and late reduced diffusion.

The sigma-1 receptor: roles in neuronal plasticity and disease

Sigma-1 receptors (Sig-1Rs) have been implicated in many neurological and psychiatric conditions. Sig-1Rs are intracellular chaperones that reside specifically at the endoplasmic reticulum (ER)-mitochondrion interface, referred to as the mitochondrion-associated ER membrane (MAM). Here, Sig-1Rs regulate ER-mitochondrion Ca(2+) signaling. In this review, we discuss the current understanding of Sig-1R functions. Based on this, we suggest that the key cellular mechanisms linking Sig-1Rs to neurological disorders involve the translocation of Sig-1Rs from the MAM to other parts of the cell, whereby Sig-1Rs bind and modulate the activities of various ion channels, receptors, or kinases. Thus, Sig-1Rs and their associated ligands may represent new avenues for treating aspects of neurological and psychiatric diseases.

Recent Non-Interventional Advances in Cancer Pain Among Singapore Patients

Introduction: Pain is a common symptom in cancer patients, but very little information about the prevalence, severity, and treatment of pain in cancer patients in Singapore is available. Therefore, our prospective survey in the National Cancer Centre (NCC) outpatients is incorporated in this report. In addition, a review concerning the recent advances on non-interventional pain management in cancer treatment, which is relevant in the context, is discussed. Materials and Methods: For the prospective survey, a questionnaire was distributed for self-administration by patients while waiting for consultation at the NCC outpatient departments. Literature searches on advances in pain management were conducted, reviewed and discussed. Results: In the last decade, there have been advances in pain pharmacology ranging from wider therapeutic options and management approaches to novel delivery techniques. Acupuncture and massage therapy became increasingly popular among cancer patients. Some clinical trials of acupuncture show benefits in palliation of cancer pain. From the prospective survey, 41.2% of the responders reported pain in the past week, and only 70.8% talked to their doctors about their pain. One third of the patients received analgesics. Of these, 86.5% said that they were taking the prescribed medications, however, 37.4% admitted to having difficulties taking them. Non-drug methods were used by 25.4% of the patients. Medicated oil, cream or gel was used by 49.3%; only 2.6% reported use of Chinese herbs. Conclusion: Pain is a significant symptom in outpatients attending a cancer centre, affecting 41.2% of the patients. Although majority of patients who suffered from pain reported this to doctors, much more medical effort is needed to help patients to relieve their pain and proper complementary therapy could be considered. Key words: Cancer outpatients, Complementary therapies, Non-pharmacological pain treatments, Pain prevalence

Psychopharmacological treatment and psychological interventions in irritable bowel syndrome

Irritable bowel syndrome (IBS) accounts for 25% of gastroenterology output practice, making it one of the most common disorders in this practice. Psychological and social factors may affect the development of this chronic disorder. Furthermore, psychiatric symptoms and psychiatric diseases are highly prevalent in this condition, but the approach to treating these is not always straightforward. As emphasized in the biopsychosocial model of IBS, with regard to the modulatory role of stress-related brain-gut interactions and association of the disease with psychological factors and emotional state, it proves useful to encourage psychopharmacological treatments and psychosocial therapies, both aiming at reducing stress perception. The aim of this paper is to analyze the effectiveness of psychopharmacological treatment and psychological interventions on irritable bowel syndrome.

Human experimental pain models for assessing the therapeutic efficacy of analgesic drugs

Pain models in animals have shown low predictivity for analgesic efficacy in humans, and clinical studies are often very confounded, blurring the evaluation. Human experimental pain models may therefore help to evaluate mechanisms and effect of analgesics and bridge findings from basic studies to the clinic. The present review outlines the concept and limitations of human experimental pain models and addresses analgesic efficacy in healthy volunteers and patients. Experimental models to evoke pain and hyperalgesia are available for most tissues. In healthy volunteers, the effect of acetaminophen is difficult to detect unless neurophysiological methods are used, whereas the effect of nonsteroidal anti-inflammatory drugs could be detected in most models. Anticonvulsants and antidepressants are sensitive in several models, particularly in models inducing hyperalgesia. For opioids, tonic pain with high intensity is attenuated more than short-lasting pain and nonpainful sensations. Fewer studies were performed in patients. In general, the sensitivity to analgesics is better in patients than in healthy volunteers, but the lower number of studies may bias the results. Experimental models have variable reliability, and validity shall be interpreted with caution. Models including deep, tonic pain and hyperalgesia are better to predict the effects of analgesics. Assessment with neurophysiologic methods and imaging is valuable as a supplement to psychophysical methods and can increase sensitivity. The models need to be designed with careful consideration of pharmacological mechanisms and pharmacokinetics of analgesics. Knowledge obtained from this review can help design experimental pain studies for new compounds entering phase I and II clinical trials.

Targeting ligand-operated chaperone sigma-1 receptors in the treatment of neuropsychiatric disorders

INTRODUCTION

Current drugs for the treatment of psychiatric or neurodegenerative disorders have limitations. Psychotherapeutic drugs such as typical and atypical antipsychotics, tricyclic antidepressants and selective monoamine reuptake inhibitors, aim to normalize the hyper- or hypo-neurotransmission of monoaminergic systems. Despite their contribution to the outcomes of psychiatric patients, these agents often exert severe side effects and require chronic treatments to promote amelioration of symptoms. Drugs available for the treatment of neurodegenerative disorders are severely limited.

AREAS COVERED

Recent evidence that has shed light on sigma-1 receptor ligands, which may serve as a new class of antidepressants or neuroprotective agents. Sigma-1 receptors are novel ligand-operated molecular chaperones regulating signal transduction, ER stress, cellular redox, cellular survival and synaptogenesis. Selective sigma-1 receptor ligands exert rapid antidepressant-like, anxiolytic, antinociceptive and robust neuroprotective actions in preclinical studies. Recent studies that suggest that reactive oxygen species might play a role as signal integrators downstream of Sig-1Rs are also covered.

EXPERT OPINION

The advances in sigma receptor research in the last decade have begun to elucidate the intracellular signal cascades upstream and downstream of sigma-1 receptors. The novel ligand-operated properties of the sigma-1 receptor chaperone may enable interventions by which stress-related cellular systems can be pharmacologically controlled.

Dextromethorphan efficiently increases bactericidal activity, attenuates inflammatory responses, and prevents group a streptococcal sepsis

Group A streptococcus (GAS) is an important human pathogen that causes a wide spectrum of diseases, ranging from mild throat and skin infections to severe invasive diseases such as necrotizing fasciitis and streptococcal toxic shock syndrome. Dextromethorphan (DM), a dextrorotatory morphinan and a widely used antitussive drug, has recently been reported to possess anti-inflammatory properties. In this study, we investigated the potential protective effect of DM in GAS infection using an air pouch infection mouse model. Our results showed that DM treatment increased the survival rate of GAS-infected mice. Bacterial numbers in the air pouch were lower in mice treated with DM than in those infected with GAS alone. The bacterial elimination efficacy was associated with increased cell viability and bactericidal activity of air-pouch-infiltrating cells. Moreover, DM treatment prevented bacterial dissemination in the blood and reduced serum levels of the proinflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and IL-1β and the chemokines monocyte chemotactic protein 1 (MCP-1), macrophage inflammatory protein 2 (MIP-2), and RANTES. In addition, GAS-induced mouse liver injury was reduced by DM treatment. Taken together, DM can increase bacterial killing and reduce inflammatory responses to prevent sepsis in GAS infection. The consideration of DM as an adjunct treatment in combination with antibiotics against bacterial infection warrants further study.

Novel N-methyl-D-aspartate receptor antagonists: a review of compounds patented since 2006

IMPORTANCE OF THE FIELD

The NMDA receptor is a complex ligand gated, voltage-dependent ion channel. It has been a drug target for > 25 years for neurological and psychiatric indications. Whereas the initial optimism to turn preclinically active compounds rapidly into drugs for human use was dampened, new insights into cellular receptor localization, role of subunits and receptor operation have kept the interest alive to modulate this receptor for therapeutic intervention.

AREAS COVERED IN THIS REVIEW

The article describes the NMDA receptor antagonists patented since 2006. Also included are novel NMDA receptor ligands potentially useful for positron emission tomography imaging.

WHAT THE READER WILL GAIN

The first section summarizes the current status of NMDA receptor pharmacology. This serves as a base for the next sections discussing the patented compounds with respect to their mode of action, potency and, in some cases, drugability.

TAKE HOME MESSAGE

The most important recent strategies aiming for inhibition of NMDA receptor-mediated neurotransmission avoid for safety reasons full receptor blockade but allow a low degree of normal receptor function. Approaches pursued by the latest patents comprise blocking the channel with compounds of low affinity, antagonizing receptor activity by highly potent NR2B ligands, partial agonism at the glutamate or glycine-binding site and improvement of pharmacokinetic properties of well established, safe antagonists by deuteration.

Recent developments in the inhibitors of neuroinflammation and neurodegeneration: inflammatory oxidative enzymes as a drug target

IMPORTANCE OF THE FIELD

Increasing evidence indicates that glial cells play a pivotal role in a wide range of brain diseases. As glial cells orchestrate inflammatory responses in the CNS, recent studies have focused on glial cells and neuroinflammation as drug targets for the treatment of neuroinflammatory and neurodegenerative diseases.

AREAS COVERED IN THIS REVIEW

In this review, we aim to give an overview of the current literature and patents for inhibitors of inflammatory oxidative enzymes in glia such as NADPH oxidase, myeloperoxidase, COX-2 and 5-lipooxygenase.

WHAT THE READER WILL GAIN

Recent literature and patents on natural products or small molecule-based inhibitors of glial oxidative enzymes are reviewed.

TAKE HOME MESSAGE

Extensive studies and patents recently reported in this field suggest that glial inhibitors may soon proceed to clinical trials. However, before glial inhibitors can serve as novel drugs for the treatment of neuroinflammatory disorders, the neurotoxic and neuroprotective effects of glial neuroinflammatory responses need to be better dissected.