-
Cells Jun 2023Memantine is an FDA-approved, non-competitive NMDA-receptor antagonist that has been shown to have mitochondrial protective effects, improve cell viability and enhance...
Memantine is an FDA-approved, non-competitive NMDA-receptor antagonist that has been shown to have mitochondrial protective effects, improve cell viability and enhance clearance of Aβ peptide. Currently, there are uncertainties regarding the precise molecular targets as well as the most favourable treatment concentrations of memantine. Here, we made use of an imaging-based approach to investigate the concentration-dependent effects of memantine on mitochondrial fission and fusion dynamics, autophagy and mitochondrial quality control using a neuronal model of CCCP-induced mitochondrial injury so as to better unpack how memantine aids in promoting neuronal health. GT1-7 murine hypothalamic cells were cultured under standard conditions, treated with a relatively high and low concentration (100 µM and 50 µM) of memantine for 48 h. Images were acquired using a Zeiss 780 PS1 platform. Utilising the mitochondrial event localiser (MEL), we demonstrated clear concentration-dependent effects of memantine causing a protective response to mitochondrial injury. Both concentrations maintained the mitochondrial network volume whilst the low concentration caused an increase in mitochondrial number as well as increased fission and fusion events following CCCP-induced injury. Additionally, we made use of a customised Python-based image processing and analysis pipeline to quantitatively assess memantine-dependent changes in the autophagosomal and lysosomal compartments. Our results revealed that memantine elicits a differential, concentration-dependent effect on autophagy pathway intermediates. Intriguingly, low but not high concentrations of memantine lead to the induction of mitophagy. Taken together, our findings have shown that memantine is able to protect the mitochondrial network by preserving its volume upon mitochondrial injury with high concentrations of memantine inducing macroautophagy, whereas low concentrations lead to the induction of mitophagy.
Topics: Mice; Animals; Mitophagy; Memantine; Carbonyl Cyanide m-Chlorophenyl Hydrazone; Autophagy; Mitochondria
PubMed: 37443760
DOI: 10.3390/cells12131726 -
Drug Design, Development and Therapy 2016Currently available therapies for the treatment of Alzheimer's disease (AD) consist of cholinesterase inhibitors (ChEIs), such as donepezil, and the -methyl-D-aspartate... (Review)
Review
Currently available therapies for the treatment of Alzheimer's disease (AD) consist of cholinesterase inhibitors (ChEIs), such as donepezil, and the -methyl-D-aspartate receptor antagonist memantine. In December 2014, the US Food and Drug Administration approved Namzaric™, a once-daily, fixed-dose combination (FDC) of memantine extended-release (ER) and donepezil for patients with moderate-to-severe AD. The FDC capsule is bioequivalent to the coadministered individual drugs, and its bioavailability is similar when taken fasting, with food, or sprinkled onto applesauce. The combination of memantine and ChEIs in moderate-to-severe AD provides additional benefits to ChEI monotherapy across multiple domains and may delay the time to nursing home admission. A dedicated study of memantine ER compared to placebo in patients on a stable dose of a ChEI found statistically significant benefits on cognition and global status but not functioning. Treatment with memantine ER and donepezil is generally well tolerated, although higher doses of ChEIs are associated with more serious adverse events such as vomiting, syncope, and weight loss. Potential advantages of the FDC include a simpler treatment regimen, reduction in pill burden, and the ability to sprinkle the capsule onto soft foods. Patients who may benefit from the FDC include those with significant dysphagia, a history of poor compliance, or limited caregiver interaction. However, available evidence that these advantages would increase treatment adherence and persistence is conflicting, meaning that the added cost of switching patients from generic options to an FDC may not always be justified.
Topics: Adolescent; Adult; Alzheimer Disease; Biological Availability; Cholinesterase Inhibitors; Cognition; Delayed-Action Preparations; Donepezil; Drug Therapy, Combination; Female; Humans; Indans; Male; Memantine; Middle Aged; Nootropic Agents; Piperidines; Severity of Illness Index; Young Adult
PubMed: 27757016
DOI: 10.2147/DDDT.S86463 -
Biomolecules Jul 2020Memantine, an -methyl-d-aspartate (NMDA) receptor antagonist approved for treating Alzheimer's disease, has a good safety profile and is increasingly being studied for... (Review)
Review
Memantine, an -methyl-d-aspartate (NMDA) receptor antagonist approved for treating Alzheimer's disease, has a good safety profile and is increasingly being studied for possible use in a variety of non-dementia psychiatric disorders. There is an abundance of basic and clinical data that support the hypothesis that NMDA receptor hypofunction contributes to the pathophysiology of schizophrenia. However, there are numerous randomized, double-blind, placebo-controlled clinical trials showing that add-on treatment with memantine improves negative and cognitive symptoms, particularly the negative symptoms of schizophrenia, indicating that memantine as adjunctive therapy in schizophrenia helps to ameliorate negative symptoms and cognitive deficits. It remains unclear why memantine does not show undesirable central nervous system (CNS) side effects in humans unlike other NMDA receptor antagonists, such as phencyclidine and ketamine. However, the answer could lie in the fact that it would appear that memantine works as a low-affinity, fast off-rate, voltage-dependent, and uncompetitive antagonist with preferential inhibition of extrasynaptic receptors. It is reasonable to assume that the effects of memantine as adjunctive therapy on negative symptoms and cognitive deficits in schizophrenia may derive primarily, if not totally, from its NMDA receptor antagonist activity at NMDA receptors including extrasynaptic receptors in the CNS.
Topics: Animals; Antipsychotic Agents; Drug Combinations; Excitatory Amino Acid Antagonists; Humans; Memantine; Receptors, N-Methyl-D-Aspartate; Schizophrenia
PubMed: 32751985
DOI: 10.3390/biom10081134 -
Current Opinion in Pharmacology Feb 2015The clinical benefits of the glutamate receptor antagonists memantine and ketamine have helped sustain optimism that glutamate receptors represent viable targets for... (Comparative Study)
Comparative Study Review
The clinical benefits of the glutamate receptor antagonists memantine and ketamine have helped sustain optimism that glutamate receptors represent viable targets for development of therapeutic drugs. Both memantine and ketamine antagonize N-methyl-D-aspartate receptors (NMDARs), a glutamate receptor subfamily, by blocking the receptor-associated ion channel. Although many of the basic characteristics of NMDAR inhibition by memantine and ketamine appear similar, their effects on humans and to a lesser extent on rodents are strongly divergent. Some recent research suggests that preferential inhibition by memantine and ketamine of distinct NMDAR subpopulations may contribute to the drugs' differential clinical effects. Here we review studies that shed light on possible explanations for differences between the effects of memantine and ketamine.
Topics: Animals; Drug Design; Excitatory Amino Acid Antagonists; Humans; Ketamine; Memantine; Molecular Targeted Therapy; Receptors, N-Methyl-D-Aspartate
PubMed: 25462293
DOI: 10.1016/j.coph.2014.11.006 -
Neuropsychopharmacology : Official... Dec 2020The uncompetitive low-affinity NMDA receptor antagonist, memantine, acutely increases electrophysiological measures of auditory information processing in both healthy... (Randomized Controlled Trial)
Randomized Controlled Trial
The uncompetitive low-affinity NMDA receptor antagonist, memantine, acutely increases electrophysiological measures of auditory information processing in both healthy subjects (HS) and patients with schizophrenia. Memantine effects on functional measures of auditory discrimination performance and learning are not known; conceivably, beneficial effects on these measures might suggest a role for memantine in augmenting the cognitive and functional impact of auditory targeted cognitive training (TCT). Here, carefully characterized HS (n = 20) and schizophrenia patients (n = 22) were tested in measures of auditory discrimination performance (words-in-noise (WIN), quick speech-in-noise (QuickSIN), gaps-in-noise) and auditory frequency modulation learning (a component of TCT) on 2 days about a week apart, after ingesting either placebo or 20 mg memantine po, in a double-blind, within-subject cross-over random order design. Memantine modestly enhanced functional measures of auditory discrimination in both schizophrenia patients (WIN) and HS (WIN and QuickSIN), as well as auditory frequency modulation learning in schizophrenia patients. These findings converge with a growing literature showing that memantine can enhance a range of metrics of auditory function. These properties could contribute to the apparent benefits of memantine as an adjunctive treatment in schizophrenia, and suggest that memantine might augment learning and potentially clinical gains from auditory-based TCT.
Topics: Auditory Perception; Discrimination, Psychological; Double-Blind Method; Humans; Memantine; Receptors, N-Methyl-D-Aspartate; Schizophrenia
PubMed: 32961542
DOI: 10.1038/s41386-020-00865-8 -
Neuropharmacology Feb 2024The great potential for NMDA receptor modulators as druggable targets in neurodegenerative disorders has been met with limited success. Considered one of the rare... (Review)
Review
The great potential for NMDA receptor modulators as druggable targets in neurodegenerative disorders has been met with limited success. Considered one of the rare exceptions, memantine has consistently demonstrated restorative and prophylactic properties in many AD models. In clinical trials memantine slows the decline in cognitive performance associated with AD. Here, we provide an overview of the basic properties including pharmacological targets, toxicology and cellular effects of memantine. Evidence demonstrating reductions in molecular, physiological and behavioural indices of AD-like impairments associated with memantine treatment are also discussed. This represents both an extension and homage to Dr. Chris Parson's considerable contributions to our fundamental understanding of a success story in the AD treatment landscape.
Topics: Humans; Memantine; Alzheimer Disease; Receptors, N-Methyl-D-Aspartate; Cognition
PubMed: 37832633
DOI: 10.1016/j.neuropharm.2023.109737 -
Journal of Affective Disorders Jun 2016Acetylcholinesterase inhibitors (AceI) and memantine might prove useful in bipolar disorder (BD) given their neuroprotective and pro-cognitive effects, as highlighted by... (Meta-Analysis)
Meta-Analysis Review
Acetylcholinesterase inhibitors and memantine in bipolar disorder: A systematic review and best evidence synthesis of the efficacy and safety for multiple disease dimensions.
BACKGROUND
Acetylcholinesterase inhibitors (AceI) and memantine might prove useful in bipolar disorder (BD) given their neuroprotective and pro-cognitive effects, as highlighted by several case reports. We aimed to systematically review the efficacy and safety of AceI and memantine across multiple outcome dimensions in BD.
METHODS
Systematic PubMed and SCOPUS search until 04/17/2015 without language restrictions. Included were randomized controlled trials (RCTs), open label studies and case series of AceI or memantine in BD patients reporting quantitative data on depression, mania, psychotic symptoms, global functioning, or cognitive performance. We summarized results using a best-evidence based synthesis.
RESULTS
Out of 214 hits, 12 studies (RCTs=5, other designs=7, total n=422) were included. Donepezil (studies=5; treated=102 vs. placebo=21): there was strong evidence for no effect on mania and psychotic symptoms; low evidence indicating no effect on depression. Galantamine (studies=3; treated=21 vs. controls=20) (placebo=10, healthy subjects=10): there was strong evidence for no effect on mania; moderate evidence for no effect on depression; low evidence for no effect on global functioning. Memantine (studies=4; treated=152 vs. placebo=88): there was conflicting evidence regarding efficacy for mania, depression and global functioning.
LIMITATIONS
Paucity of RCTs; small sample size studies; heterogeneous design, outcome and patient characteristics.
CONCLUSION
There is limited but converging evidence of no effect of AceI in BD, and conflicting evidence about memantine in BD. Too few studies of mostly medium/low quality and lacking sufficient numbers of patients in specific mood states, especially mania, contributed data, focusing solely on short-term/medium-term treatment, necessitating additional high-quality research to yield more definite results.
Topics: Adult; Bipolar Disorder; Case-Control Studies; Cholinesterase Inhibitors; Clinical Trials as Topic; Depression; Depressive Disorder; Donepezil; Evidence-Based Medicine; Excitatory Amino Acid Antagonists; Female; Galantamine; Humans; Indans; Male; Memantine; Middle Aged; Piperidines; Psychotic Disorders; Randomized Controlled Trials as Topic; Treatment Outcome
PubMed: 27010579
DOI: 10.1016/j.jad.2016.03.034 -
PloS One 2015We performed an updated meta-analysis of randomized placebo-controlled trials testing memantine monotherapy for patients with Alzheimer's disease (AD). (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
We performed an updated meta-analysis of randomized placebo-controlled trials testing memantine monotherapy for patients with Alzheimer's disease (AD).
METHODS
The meta-analysis included randomized controlled trials of memantine monotherapy for AD, omitting those in which patients were also administered a cholinesterase inhibitor. Cognitive function, activities of daily living, behavioral disturbances, global function, stage of dementia, drug discontinuation rate, and individual side effects were compared between memantine monotherapy and placebo groups. The primary outcomes were cognitive function and behavioral disturbances; the others were secondary outcomes.
RESULTS
Nine studies including 2433 patients that met the study's inclusion criteria were identified. Memantine monotherapy significantly improved cognitive function [standardized mean difference (SMD)=-0.27, 95% confidence interval (CI)=-0.39 to -0.14, p=0.0001], behavioral disturbances (SMD=-0.12, 95% CI=-0.22 to -0.01, p=0.03), activities of daily living (SMD=-0.09, 95% CI=-0.19 to -0.00, p=0.05), global function assessment (SMD=-0.18, 95% CI=-0.27 to -0.09, p=0.0001), and stage of dementia (SMD=-0.23, 95% CI=-0.33 to -0.12, p=0.0001) scores. Memantine was superior to placebo in terms of discontinuation because of inefficacy [risk ratio (RR)=0.36, 95% CI=0.17¬ to 0.74, p=0.006, number needed to harm (NNH)=non significant]. Moreover, memantine was associated with less agitation compared with placebo (RR=0.68, 95% CI=0.49 to 0.94, p=0.02, NNH=non significant). There were no significant differences in the rate of discontinuation because of all causes, all adverse events, and individual side effects other than agitation between the memantine monotherapy and placebo groups.
CONCLUSIONS
Memantine monotherapy improved cognition, behavior, activities of daily living, global function, and stage of dementia and was well-tolerated by AD patients. However, the effect size in terms of efficacy outcomes was small and thus there is limited evidence of clinical benefit.
Topics: Activities of Daily Living; Alzheimer Disease; Humans; Memantine; Publication Bias; Randomized Controlled Trials as Topic; Treatment Outcome
PubMed: 25860130
DOI: 10.1371/journal.pone.0123289 -
Science Advances Dec 2023Cortical spreading depolarization (CSD) is a promising target for neuroprotective therapy in traumatic brain injury (TBI). We explored the effect of NMDA receptor...
Cortical spreading depolarization (CSD) is a promising target for neuroprotective therapy in traumatic brain injury (TBI). We explored the effect of NMDA receptor antagonism on electrically triggered CSDs in healthy and brain-injured animals. Rats received either one moderate or four daily repetitive mild closed head impacts (rmTBI). Ninety-three animals underwent craniectomy with electrocorticographic (ECoG) and local blood flow monitoring. In brain-injured animals, ketamine or memantine inhibited CSDs in 44 to 88% and 50 to 67% of cases, respectively. Near-DC/AC-ECoG amplitude was reduced by 44 to 75% and 52 to 67%, and duration by 39 to 87% and 61 to 78%, respectively. Daily memantine significantly reduced spreading depression and oligemia following CSD. Animals ( = 31) were randomized to either memantine (10 mg/kg) or saline with daily neurobehavioral testing. Memantine-treated animals had higher neurological scores. We demonstrate that memantine improved neurovascular function following CSD in sham and brain-injured animals. Memantine also prevented neurological decline in a blinded, preclinical randomized rmTBI trial.
Topics: Rats; Animals; Memantine; Brain Injuries, Traumatic; Brain; Electrocorticography; Receptors, N-Methyl-D-Aspartate
PubMed: 38091390
DOI: 10.1126/sciadv.adj2417 -
Schizophrenia Research Aug 2014The Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) and Treatment Units for Research on Neurocognition and Schizophrenia projects were... (Review)
Review
The Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) and Treatment Units for Research on Neurocognition and Schizophrenia projects were designed to facilitate the development of new drugs for the treatment of cognitive impairments in people with schizophrenia. The MATRICS project identified three drug mechanisms of particular interest: dopaminergic, cholinergic, and glutamatergic. As a group, while people with schizophrenia have moderate cognitive impairment, it is the best predictor of long-term outcome. Unfortunately, there are no approved medications for cognitive impairment in this population. Hence, the development of new pharmacological approaches is critical for reducing illness-related disability. The combination of an acetylcholinesterase inhibitor (AChEI) and memantine is more effective than either medication alone to improve cognition in Alzheimer's dementia. Galantamine is not only an AChEI, but also a positive allosteric modulator of the α4β2 and α7 nicotinic receptors. Hypofunction of N-methyl-d-aspartate (NMDA) receptors has been implicated in the pathophysiology of cognitive symptoms in schizophrenia and hence memantine may positively impact cognition. Memantine decreases the tonic NMDA current and galantamine enhances the action potential mediated by a postsynaptic NMDA current. This results in an increased signal transmission; therefore, a greater signal-to-noise ratio occurs with the combination than memantine alone. Galantamine improves the α-amino-3-hydroxy-5-methyl-4-isoxazol-propionate (AMPA)-mediated signaling which could be neuroprotective and may improve memory coding. The combination of galantamine and memantine may be particularly effective in schizophrenia in order to increase the selective cognition enhancement produced by either medication alone. In the future, multitarget-directed ligands may play a role in the treatment of complex diseases like schizophrenia.
Topics: Animals; Cognition Disorders; Drug Therapy, Combination; Galantamine; Humans; Memantine; Nootropic Agents; Randomized Controlled Trials as Topic; Schizophrenia
PubMed: 24878431
DOI: 10.1016/j.schres.2014.04.037