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PubMed2006

Behavioral effects of memantine in Alzheimer disease patients receiving donepezil treatment.

OBJECTIVE: To investigate the behavioral effects of memantine in moderate to severe Alzheimer disease (AD). METHODS: The authors conducted a hypothesis-generating, exploratory analysis of a 24-week, double-blind, placebo-controlled trial comparing memantine (20 mg/day) with placebo in subjects with moderate to severe AD on stable donepezil treatment. They employed the Neuropsychiatric Inventory (NPI; 12-item), administered at baseline, week 12, and week 24, to assess the effects of memantine on behavior. Global, cognitive, and functional measures were collected and relationships between these assessments and changes in behavior were determined. The intent-to-treat population was examined using last-observation-carried-forward and observed-cases approaches. RESULTS: Patients treated with memantine had significantly lower NPI total scores than patients treated with placebo. Analyses of the 12 NPI domains revealed significant effects in favor of memantine on agitation/aggression, eating/appetite, and irritability/lability. Of patients who exhibited agitation/aggression at baseline, those treated with memantine showed significant reduction of symptoms compared with placebo-treated patients. Memantine-treated patients without agitation/aggression at baseline evidenced significantly less emergence of this symptom compared with similar patients receiving placebo. Caregivers of patients receiving memantine registered significantly less agitation-related distress. There were significant relationships between the NPI and the global rating scale and performance of activities of daily living, but not between changes in the NPI and cognition. CONCLUSION: Treatment with memantine reduced agitation/aggression, irritability, and appetite/eating disturbances. Memantine reduced agitation/aggression in patients who were agitated at baseline and delayed its emergence in those who were free of agitation at baseline.

Activities of Daily Living↗

PubMed2004

Memantine for dementia.

BACKGROUND: Alzheimer's disease, vascular and mixed dementia are the three commonest forms of dementia affecting older people. There is evidence that the excitatory activity of L-glutamate plays a role in the pathogenesis of Alzheimer's disease and in the damage from an ischaemic stroke. A low affinity antagonist to N-Methyl-D-aspartate (NMDA) type receptors, such as memantine, may prevent excitatory amino acid neurotoxicity without interfering with the physiological actions of glutamate required for memory and learning. OBJECTIVES: To determine the clinical efficacy and safety of memantine for people with Alzheimer's disease, or vascular or mixed dementia. SEARCH STRATEGY: Trials were identified from a search of the Trial-based Specialized Register of the Cochrane Dementia and Cognitive Improvement Group on 7 April 2004 using the terms: memantin*, namenda*, ebixa*, axura*, D-145, DMAA, DRG-0267. All major health care databases and many ongoing trial databases are searched regularly to keep this Register up to date. SELECTION CRITERIA: Double-blind, parallel group, placebo-controlled, randomised and unconfounded trials in which memantine was administered to people with dementia. DATA COLLECTION AND ANALYSIS: Data were extracted, pooled where possible, and weighted mean differences, standardized mean differences or odds ratios were estimated. Intention-to-treat (ITT) and observed cases (OC) analyses are reported, where data were available. MAIN RESULTS: The evidence suggests that memantine has a positive effect on cognition, mood and behaviour and the ability to perform activities of daily living in patients with moderate to severe Alzheimer's disease. The results in patients with mild to moderate vascular dementia, suggest a beneficial effect of 20mg/day of memantine on cognitive function measured at 28 weeks. However, these results are neither supported by an effect on ability to perform activities of daily living nor by an effect on the clinical impression of change. This suggests that, in patients with mild to moderate vascular dementia, the effect on cognitive function is not translated into clinically detectable changes. REVIEWERS' CONCLUSIONS: :Memantine 20 mg/day caused a clinically noticeable reduction in deterioration over 28 weeks in patients with moderate to severe Alzheimer disease. This was supported by less functional and cognitive deterioration. Patients taking memantine were less likely to become agitated. The effect in mild to moderate AD is unknown. Patients with mild to moderate vascular dementia receiving memantine 20 mg/day had less cognitive deterioration at 28 weeks but the effects were not clinically discernible. There is an early beneficial effect on cognition, mood, behaviour and clinical impression for memantine at 6 weeks. The drug is well tolerated in general and the incidence of adverse effects is low.

Activities of Daily Living↗

PubMed2005

Memantine for dementia.

BACKGROUND: Memantine, a low affinity antagonist to glutamate NMDA receptors, may prevent excitatory neurotoxicity in dementia. OBJECTIVES: To determine efficacy and safety of memantine for people with Alzheimer's disease (AD), vascular (VD) and mixed dementia. SEARCH STRATEGY: The Specialized Register of the Cochrane Dementia and Cognitive Improvement Group was searched on 20 May 2005. This register contains references from all major healthcare databases and many ongoing trial databases and is updated regularly. In addition the search engines Copernic and Google were used to identify unpublished trials through inspection of the websites of licensing bodies like the FDA , EMEA and NICE and of companies' websites (Lundbeck, Merz, Forest, Suntori etc) and clinical trials registries. SELECTION CRITERIA: Double-blind, parallel group, placebo-controlled, randomized trials of memantine in people with dementia. DATA COLLECTION AND ANALYSIS: Data were pooled where possible. Intention-to-treat (ITT) and observed case (OC) analyses are reported. MAIN RESULTS: 1. Moderate to severe AD. Two out of three six month studies show a small beneficial effect of memantine. Pooled data indicate a beneficial effect at six months on cognition (4.12 points on the 100 point SIB , 95% CI 2.14 to 5.74, P < 0.00001), activities of daily living (1.27 points on the 54 point ADCS-ADLsev, 95% CI 0.44 to 2.09, P = 0.003) and behaviour (2.76 points on the 144 NPI, 95% CI 0.88 to 4.63, P = 0.004), supported by clinical impression of change (0.28 points on the 7 point CIBIC+, 95% CI 0.15 to 0.41, P < 0.0001).2. Mild to moderate AD. In a single six month trial, memantine had a beneficial effect on ITT analysis of cognition, (1.9 ADAS-Cog points, 95% CI 0.35 to 3.45, P = 0.02) and behaviour (3.50 NPI points 95% CI 0.15 to 6.85, P = 0.04) supported by clinical global impression of change (0.30 CIBIC+ points, 95% CI 0.09 to 0.51, P = 0.005), but no effect on activities of daily living or OC analysis of cognition. The statistical significance of these benefits could be overturned by data from two unpublished studies which are known to show no significant effect. 3. Mild to moderate vascular dementia. In two six month studies, memantine improved cognition (1.85 ADAS-Cog points, 95% CI 0.88 to 2.83, P = 0.0002), and behaviour (0.84 95% CI 0.06 to 0.91, P = 0.03) but this was not supported by clinical global measures.4. Patients taking memantine appeared to be less likely to develop agitation (93/1167 [8%] versus 134/1141 [12%] (Peto odds ratio (OR): 0.65, 95% CI 0.49 to 0.86, P = 0.002). This was consistently seen in moderate to severe dementia. There were no data which suggested an effect on agitation which is already present.5. Memantine is well tolerated. AUTHORS' CONCLUSIONS: Published data suggest a small beneficial effect of memantine at six months in moderate to severe AD. The beneficial effect on cognition in patients with mild to moderate vascular dementia was not detectable on global assessment at six months. Whether memantine has any effect in mild to moderate AD is unknown.

Activities of Daily Living↗

PubMed2004

Inhibitory effects of memantine on human cytochrome P450 activities: prediction of in vivo drug interactions.

OBJECTIVE: The aim of the present study was to predict the drug interaction potential of memantine by elucidation of its inhibitory effects on cytochrome P450 enzymes using pooled human liver microsomes (HLM) and recombinant P450s. METHODS: The inhibitory potency of memantine on CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 activities was examined with specific probe drugs in HLM and recombinant P450s. The in vivo drug interactions of memantine were predicted in vitro using the [ I]/([ I] + KI) values. RESULTS: In HLM, memantine inhibited CYP2B6 and CYP2D6 activities, with KI (IC50) values of 76.7 (279.7) and 94.9 (368.7) microM, respectively. Both inhibitions were competitive. In addition, cDNA-expressed P450s were used to confirm these results. Memantine strongly inhibited recombinant CYP2B6 activity with IC50 ( KI) value of 1.12 (0.51) microM and activity of recombinant CYP2D6 with IC50 (KI) value of 242.4 (84.4) microM. With concentrations up to 1,000 microM, memantine showed no appreciable effect on CYP1A2, CYP2E1, CYP2C9, or CYP3A4 activities and a slight decrease of CYP2A6 and CYP2C19 activities. Based on [ I]/([ I] + KI) values calculated using peak total plasma concentration (or enzyme-available concentration in the liver) of memantine and the KI obtained in HLM, 1.3 (13.5), and 1.0% (11.2%), inhibition of the clearance of CYP2B6 and CYP2D6 substrates could be expected, respectively. Nevertheless, when considering KI values obtained from cDNA-expressed CYP2B6, as generally recommended, even 66.2% (95.9%) decrease in metabolism of coadministered CYP2B6 substrates could be anticipated. CONCLUSION: Memantine exerts selective inhibition of CYP2B6 activity at clinically relevant concentrations, suggesting the potential for clinically significant drug interactions. Inhibition of other CYPs during memantine therapy is unlikely. Moreover, memantine represents a new, potent, selective inhibitor of recombinant CYP2B6, which may prove useful for screening purposes during early phases of in vitro drug metabolism studies with new chemical entities.

Antiparkinson Agents↗

PubMed2004

Lack of pharmacokinetic or pharmacodynamic interaction between memantine and donepezil.

BACKGROUND: Memantine, a low- to moderate-affinity, uncompetitive N-methyl-D-aspartate receptor antagonist, was approved in the US for treatment of moderate to severe Alzheimer's disease in October 2003. OBJECTIVE: To determine whether an in vivo pharmacokinetic interaction exists between memantine and the acetylcholinesterase (AChE) inhibitor donepezil. METHODS: In this open-label, multiple-dose study, 24 healthy subjects (aged 18-35 y) received oral administration of memantine 10 mg on day 1. Following a 14-day washout period, subjects were orally administered donepezil 5 mg once daily for 7 days on an outpatient basis. Beginning on day 22, the donepezil dosage was doubled for 22 days to the target dose of 10 mg once daily, with the last donepezil dose concomitantly administered with memantine 10 mg on day 43. Assessments included pharmacokinetic as well as safety parameters. In addition, AChE inhibition was measured in red blood cells by radiolabeled-enzyme assay following administration of donepezil alone and after a single memantine dose. RESULTS: Data from 19 subjects who completed the study indicated no significant pharmacokinetic interactions between a single dose of memantine and multiple doses of donepezil. Percent maximum inhibition of AChE activity (mean +/- SD) by donepezil was 77.8 +/- 7.3% and not significantly different upon coadministration of a single dose of memantine (81.1 +/- 5.7%). Two subjects withdrew due to adverse events while taking donepezil alone. Single memantine doses administered with multiple donepezil doses were well tolerated. CONCLUSIONS: The pharmacokinetic and pharmacodynamic data from this study indicated a lack of interaction between memantine and donepezil, suggesting that memantine and donepezil may be safely and effectively used in combination.

Acetylcholinesterase↗

PubMed2003

Resource utilisation and cost analysis of memantine in patients with moderate to severe Alzheimer's disease.

BACKGROUND: Alzheimer's disease (AD) is a devastating illness that causes enormous emotional stress to affected families and is associated with substantial medical and nonmedical costs. OBJECTIVE: To determine the effects of 28 weeks of memantine treatment for patients with AD on resource utilisation and costs. STUDY DESIGN AND METHODS: Multicentre, prospective, double-blind, randomised, placebo-controlled clinical trial performed in the US. The Wilcoxon-Mann-Whitney test was used to examine the resource utilisation variables and logistic regression models were used for multivariate resource utilisation analyses. Analysis of covariance (ANCOVA) models (log and non-log) were computed to examine costs from a societal perspective. All costs were calculated in 1999 US dollars. STUDY POPULATION: Outpatients with moderate to severe AD. Overall, 252 patients received randomised treatment, and 166 patients (placebo n = 76, memantine n = 90) formed the treated-per-protocol (TPP) subset for the health economic analyses, on which the main cost analysis was based. MAIN OUTCOME MEASURE: Resource Utilisation in Dementia (RUD) scale, measuring patient and caregiver resource utilisation, and various sources for cost calculations. RESULTS: Controlling for baseline differences between the groups, significantly less caregiver time was needed for patients receiving memantine than for those receiving placebo (difference 51.5 hours per month; 95% CI -95.27, -7.17; p = 0.02). Analysis of residential status also favoured memantine: time to institutionalisation (p = 0.052) and institutionalisation at week 28 (p = 0.04 with the chi-square test). Total costs from a societal perspective were lower in the memantine group (difference dollars US 1089.74/month [non-overlapping 95% CI for treatment difference -1954.90, -224.58]; p = 0.01). The main differences between the groups were total caregiver costs (dollars US-823.77/month; p = 0.03) and direct nonmedical costs (dollars US-430.84/month; p = 0.07) favouring memantine treatment. Patient direct medical costs were higher in the memantine group (p < 0.01), mainly due to the cost of memantine. CONCLUSION: Resource utilisation and total health costs were lower in the memantine group than the placebo group. The results suggest that memantine treatment of patients with moderate to severe AD is cost saving from a societal perspective.

Activities of Daily Living↗

PubMed2005

Memantine: a pharmacoeconomic review of its use in moderate-to-severe Alzheimer's disease.

Memantine (Ebixa, Namenda, Axura) is an uncompetitive NMDA receptor antagonist used in the management of patients with moderate-to-severe Alzheimer's disease. It is currently the only drug approved for use in these more advanced stages of the disease. Significant reductions in functional and cognitive decline have been demonstrated with memantine relative to placebo in randomised, double-blind trials in this patient population. Clinical trial and postmarketing surveillance data indicate that the drug is generally well tolerated. Two fully published modelled cost-effectiveness analyses of memantine in moderate-to-severe Alzheimer's disease have been conducted in the UK and Finland, in which patient progression was simulated through health states related to dependency, residential setting and cognitive function. Although the specific costs included in the analyses varied, as did the study perspective and geographical location, results of the base-case analyses consistently showed that memantine was dominant over no pharmacological treatment. In the UK and Finnish analyses, memantine increased the duration of independence by 1.3 and 4.1 months, respectively, and the time to institutionalisation by 0.8 and 1 month. Mean total per-patient costs were reduced by 1963 pounds over 2 years (2003 costs) in the UK analysis and by 1687 eurossover 5 years (2001 costs) in the Finnish analysis. Memantine was also associated with a small gain in quality-adjusted life expectancy in the UK model. In sensitivity analyses, memantine remained dominant for almost all plausible changes to key variables. Memantine reduced total societal costs by $1090 per patient per month (1999 costs) compared with no pharmacological treatment over 28 weeks in a resource utilisation and cost analysis conducted alongside a pivotal US trial in patients with moderate-to-severe Alzheimer's disease. Results were primarily driven by reductions in total caregiver costs, which included the opportunity cost of time spent in caregiving tasks, and in direct nonmedical costs, which included the cost of care in a nursing home or similar institution.In conclusion, in patients with moderate-to-severe Alzheimer's disease, memantine is associated with significant reductions in functional and cognitive decline compared with no pharmacological treatment. Available pharmacoeconomic data from Europe and the US, despite some inherent limitations, support the use of memantine as a cost-effective treatment in this patient population, although definitive conclusions are not feasible because of limited data.

Alzheimer Disease↗

PubMed1992

Memantine in the treatment of mild to moderate dementia syndrome. A double-blind placebo-controlled study.

The efficacy and the tolerability of memantine (1-amino-3,5-dimethyladamantane hydrochloride, Akatinol Memantine, CAS 41100-52-1) were investigated in patients with mild to moderate dementia syndrome in a randomized two-centre placebo-controlled clinical study. The test substance was administered at a dose of 10 mg/d from day 1 to day 3 and then at a dose of 2 x 10 mg/d from day 4 to the end of treatment after 42 days. Altogether, 88 patients were recruited to the study; their average age was 71.5 years. The efficacy of memantine was judged on the basis of the baseline/6 week differences in the total sum scores of the Clinical Assessment Geriatric Scale (SCAG), the Gottfries-Bräne-Steen Scale (GBS), the SCAG and GBS subscales and the global assessment of the change in the patient's condition. The effects of memantine on performance were studied with the aid of psychomotor tests and a behaviour investigation relating to activities of daily living (ADL). The tolerability of memantine was assessed on the basis of the doctor's global assessment and of entries on structured documentation forms (DOTES/TWIS). Further safety parameters--in the form of clinicochemical tests and measurements of blood pressure and heart rate--were also monitored during the study. On both the psychopathological measurement level (SCAG, global assessment of the change in the patient's condition) and the behavioural level (GBS), confirmatory statistical analysis brought to light significant differences between memantine and placebo (p less than or equal to 0.05), these differences showing a superiority of memantine. The tolerability of memantine was good in the main. The observed adverse reactions were not serious and, except in 3 patients, were rated as causing little or no impairment. The present clinical study demonstrates the efficacy of memantine in patients suffering from mostly moderate dementia syndrome. Clinical and statistically relevant improvements in the dementia-induced disturbances were found on the both the psychopathological level (SCAG, CGI) and the behavioural level (GBS). On the performance level also, the ADL behaviour investigation detected a highly significant improvement in the quality of performance of instrumented activities of daily living under memantine. Also the time taken to carry out these tasks was significantly reduced in comparison with placebo.

Aged↗

PubMed1992

Open-channel block of N-methyl-D-aspartate (NMDA) responses by memantine: therapeutic advantage against NMDA receptor-mediated neurotoxicity.

Excessive activation of NMDA receptors is thought to mediate the calcium-dependent neurotoxicity associated with hypoxic-ischemic brain injury, trauma, epilepsy, and several neurodegenerative diseases. For this reason, various NMDA antagonists have been investigated for their therapeutic potential in these diseases, but heretofore none have proven to be both effective and safe. In the present study, memantine, an adamantane derivative similar to the antiviral drug amantadine, is shown to block the channels activated by NMDA receptor stimulation. From whole-cell and single-channel recording experiments, the mechanism of action of memantine is deduced to be open-channel block, similar to MK-801; however, unlike MK-801, memantine is well tolerated clinically. Compared to MK-801, memantine's safety may be related to its faster kinetics of action with rapid blocking and unblocking rates at low micromolar concentrations. Furthermore, at these levels memantine is an uncompetitive antagonist and should theoretically allow near-normal physiological NMDA activity throughout the brain even in the face of pathologically high focal concentrations of glutamate. These pharmacological properties confer upon memantine a therapeutic advantage against NMDA receptor-mediated neurotoxicity with few side effects compared with other organic NMDA open-channel blockers. Moreover, memantine is increasingly effective against escalating levels of glutamate, such as those observed during a stroke. Low micromolar concentrations of memantine, levels known to be tolerated by patients receiving the drug for the treatment of Parkinson's disease, prevent NMDA receptor-mediated neurotoxicity in cultures of rat cortical and retinal ganglion cell neurons; memantine also appears to be both safe and effective in a rat stroke model. These results suggest that memantine has considerable therapeutic potential for the myriad of clinical entities associated with NMDA receptor-mediated neurotoxicity.

Animals↗

PubMed2006

[Long-term effects of memantine therapy on neonatal rats with hypoxic-ischemic brain damage].

OBJECTIVE: Animal trials have demonstrated that memantine has neuroprotective effects on hypoxic-ischemic (HI) brain damage. Whether memantine can improve the long-term prognosis of rats with HI brain damage has not been reported. This study was designed to investigate the long-term effect of memantine therapy on neonatal rats with HI brain damage. METHODS: Sixty postnatal 7-day-old newborn rats were randomly assigned into Normal control, HI and Memantine treated groups. Memantine (20 mg/kg) was administered immediately after HI in the Memantine-treated group. All subjects received a 5-day training of Morris water maze test from 23 days old. The escape latency (EL) was recorded at 28 and 35 days old. RESULTS: The EL values of the Normal control, HI and Memantine-treated groups at 28 days old were 23.1 +/- 21.8, 35.1 +/- 5.3, and 20.6 +/- 3.4 seconds, respectively. There was a significant difference in the EL value between the HI and the Normal control groups (P < 0.05). The EL value of the Normal control, HI and Memantine-treated groups at 35 days old were 19.7 +/- 16.7, 35.6 +/- 32.3, and 16.3 +/- 13.2 seconds, respectively. A prolonged EL induced by HI still existed (P < 0.05 vs Normal controls) but memantine treatment shortened the EL (P < 0.01 vs HI group) at 35 days old. CONCLUSIONS: Administering memantine immediately after HI can markedly increase the abilities of spatial discrimination, learning and memory and improve the long-term prognosis in rats with HI brain damage.

Animals↗

PubMedDate not supplied

Cognitive response to memantine in moderate to severe Alzheimer disease patients already receiving donepezil: an exploratory reanalysis.

OBJECTIVE: To investigate the cognitive effects of the N-methyl-D-aspartate receptor antagonist, memantine, with a post-hoc exploratory reanalysis of a 24-week randomized, double-blind, placebo-controlled, parallel group clinical trial comparing memantine (20 mg per day) to placebo in patients with moderate to severe Alzheimer disease (AD) receiving treatment with the cholinesterase inhibitor, donepezil. METHODS: The effects of memantine on individual items of the Severe Impairment Battery (SIB), subscale performance, and 3 post-hoc-derived aggregate subscales were investigated. Analyses were based on the intention-to-treat population using last observation carried forward and observed cases approaches. The SIB components were assessed at baseline, weeks 4, 8, 12, 18, and 24. RESULTS: The mean change from baseline by visit and at study end point on the SIB showed statistically significant differences between the memantine and placebo groups at all visits beginning at week 8 (last observation carried forward and observed cases). The SIB subscale analysis showed statistically significantly greater effects of memantine than placebo on memory, language, and praxis. When the SIB domains were aggregated using a face valid approach to create 3 higher-order subscales, memantine treatment resulted in statistically significant differences on memory, language, and praxis compared with placebo. CONCLUSIONS: These post-hoc analyses support the beneficial effects of memantine on cognition observed in a previously reported clinical trial. The results presented here suggest an effect of memantine on memory, language, and praxis in patients with moderate to severe AD and support the efficacy of memantine for the treatment of cognitive deficits in AD.

Aged↗

PubMed2006

Memantine for dementia.

BACKGROUND: Memantine, a low affinity antagonist to glutamate NMDA receptors, may prevent excitatory neurotoxicity in dementia. OBJECTIVES: To determine efficacy and safety of memantine for people with Alzheimer's disease (AD), vascular (VD) and mixed dementia. SEARCH STRATEGY: The Specialized Register of the Cochrane Dementia and Cognitive Improvement Group was searched on 8th February 2006. This register contains references from all major healthcare databases and many ongoing trial databases and is updated regularly. In addition, the search engines Copernic and Google were used to identify unpublished trials through inspection of the websites of licensing bodies like the FDA , EMEA and NICE and of companies' websites (Lundbeck, Merz, Forest, Suntori etc) and clinical trials registries. SELECTION CRITERIA: Double-blind, parallel group, placebo-controlled, randomized trials of memantine in people with dementia. DATA COLLECTION AND ANALYSIS: Data were pooled where possible. Intention-to-treat (ITT) and observed case (OC) analyses are reported. MAIN RESULTS: 1. Moderate to severe AD. Two out of three six month studies show a small beneficial effect of memantine. Pooled data indicate a beneficial effect at six months on cognition (2.97 points on the 100 point SIB, 95% CI 1.68 to 4.26, P < 0.00001), activities of daily living (1.27 points on the 54 point ADCS-ADLsev, 95% CI 0.44 to 2.09, P = 0.003) and behaviour (2.76 points on the 144 point NPI, 95% CI 0.88 to 4.63, P=0.004), supported by clinical impression of change (0.28 points on the 7 point CIBIC+, 95% CI 0.15 to 0.41, P < 0.0001).2. Mild to moderate AD. Pooled data from three unpublished studies indicate a marginal beneficial effect at six months on ITT cognition (0.99 points on the 70 point ADAS-Cog, 95% CI 0.21 to 1.78, P = 0.01) which was barely detectable clinically (0.13 CIBIC+ points, 95% CI 0.01 to 0.25, P = 0.03) but no effect on behaviour, activities of daily living or OC analysis of cognition.3. Mild to moderate vascular dementia. Pooled data from two six month studies indicated a small beneficial effect of memantine on cognition (1.85 ADAS-Cog points, 95% CI 0.88 to 2.83, P = 0.0002), and behaviour (0.84 95% CI 0.06 to 0.91, P = 0.03) but this was not supported by clinical global measures.4. Patients taking memantine were slightly less likely to develop agitation (134/1739, 7.7% versus 175/1873, 9.3% OR 0.78, 95% CI 0.61 to 0.99, P = 0.04). This effect was slightly larger, but still small, in moderate to severe AD (58/506 [12%] vs 88/499 [18%]; OR = 0.6, 95% CI 0.42 to 0.86, P = 0.005). There is no evidence either way about whether it has an effect on agitation which is already present.5. Memantine is well tolerated. AUTHORS' CONCLUSIONS: Memantine has a small beneficial effect at six months in moderate to severe AD. In patients with mild to moderate dementia, the small beneficial effect on cognition was not clinically detectable in those with vascular dementia and was detectable in those with AD. Memantine is well tolerated.

Activities of Daily Living↗

PubMed2001

The NMDA antagonist memantine attenuates the expression of opioid physical dependence in humans.

RATIONALE: Preclinical observations suggest that NMDA receptor-mediated glutamatergic neurotransmission is involved in the expression and maintenance of opioid dependence. OBJECTIVE: The present study evaluated whether memantine, the clinically available non-competitive NMDA receptor antagonist, decreases naloxone-precipitated withdrawal in morphine-dependent humans. METHODS: Eight heroin-dependent, non-treatment seeking, inpatient participants were stabilized on a fixed dose of morphine (30 mg PO qid). Subsequently, they received a series of challenges with naloxone (0.4 mg, IM) and the severity of opioid withdrawal was monitored. Either placebo or memantine (60 mg PO) was given 6 h before each naloxone challenge. A modified multiple baseline, across-participants design was used to evaluate the effects of memantine on the severity of naloxone-precipitated opioid withdrawal. RESULTS: Naloxone increased ratings and produced physical changes consistent with opioid withdrawal. Memantine attenuated the severity of opioid withdrawal as assessed with the Clinical Institute for Narcotic Withdrawal Scale scale. Withdrawal was significantly reduced when naloxone was administered at 6 and 52 h after memantine, but not when administered 126 h (5 days) after memantine. Medication effects, assessed 5 h after memantine administration and before naloxone administration, included significant increases in ratings of "strong" and "good" drug effect, and "I feel sedated", "mellow", and "high". CONCLUSIONS: Memantine attenuated the expression of opioid physical dependence in humans, indicating that glutamatergic neurotransmission at the NMDA receptor site contributes to the maintenance of opioid dependence. This finding suggests that memantine may be a useful adjunct in the treatment of opioid dependence.

Adult↗

PubMed2004

Efficacy and tolerability of memantine in the treatment of dementia.

BACKGROUND: Until recently, acetylcholinesterase inhibitors were the only approved agents for the treatment of Alzheimer's disease (AD). These medications have also been used in the treatment of vascular dementia (VD). Memantine, the first N-methyl-D-aspartate (NMDA)-receptor antagonist to be well tolerated, has been approved for the treatment of moderate to severe AD. OBJECTIVE: The aim of this study was to review the current literature on the efficacy and tolerability of memantine in the treatment of AD and VD. METHODS: A MEDLINE search of the English-language literature from January 1970 to March 2004 was conducted to identify randomized, double-blind, placebo-controlled, parallel-group trials in which memantine was administered to patients with VD or AD. The search terms were memantine, NMDA inhibitor, and NMDA antagonist. RESULTS: Excessive glutamate, the brain's major excitatory neurotransmitter, can cause excitotoxicity by allowing too much calcium to enter neuronal cells. Moderate-affinity NMDA-receptor antagonists such as memantine block pathologic activity of glutamate while allowing physiologic activity. Use of memantine has been associated with significant improvements in measures of cognition, function, and behavior in both VD and AD. Adverse events associated with memantine have been comparable to those with placebo, with the exception of an increased incidence of dizziness, constipation, cataracts, nausea, dyspnea, confusion, headache, and urinary incontinence. CONCLUSIONS: Memantine seems to be promising and well tolerated in the treatment of moderate to severe VD or AD, either as monotherapy or in combination with donepezil. It appears to be particularly effective in improving cognitive, functional, and global outcomes in moderate to severe AD and in improving cognitive end points in mild to moderate VD. More research is needed on important clinical questions, including whether memantine can prolong patients' ability to provide self-care and delay institutional placement.

Aged↗

PubMed2006

Memantine, an uncompetitive low affinity NMDA open-channel antagonist improves clinical rating scores in a multiple infarct embolic stroke model in rabbits.

The blockade of NMDA receptors has been pursued as a strategy to reduce the consequences of acute ischemic stroke (AIS) and NMDA receptors remain a valid therapeutic target to treat AIS. Because the pharmacological and toxicity profile of memantine in Alzheimer's disease patients appears to be good, we determined whether memantine would be effective at improving behavioral performance following embolic strokes in rabbits. For these studies, we used a rabbit multiple infarct ischemia model with a well-defined behavioral endpoint. In this study, memantine dissolved in PBS was given intravenously either as a bolus injection (over 1 min) or infused over 60 min. The P(50) of the control groups measured 24 h after embolization were 1.12 +/- 0.18 mg and 1.08 +/- 0.23 mg for the bolus injected and infused groups, respectively. Bolus injections of memantine at 1 mg/kg and 10 mg/kg were not effective at altering the P(50) value and memantine at a dose of 25 mg/kg was lethal. However, slowly infused memantine (25 mg/kg) significantly increased the P(50) value to 2.31 +/- 0.48 mg and 3.13 +/- 1.13 mg when given 5 and 60 min following embolization, respectively. Memantine administered 180 min following embolization also increased the P(50) value to 2.69 +/- 2.21 mg, but the response was variable. These results suggest that uncompetitive NMDA antagonists, more specifically open channel blockers, which may be alternatives to high affinity NMDA antagonists, may have substantial therapeutic benefit for the treatment of AIS and memantine or new dual activity analogs of memantine should be further pursued as a useful therapy to treat the behavioral deficits associated with multiple-infarct ischemia.

Animals↗

PubMed2005

Investigation of the pharmacokinetic and pharmacodynamic interactions between memantine and glyburide/metformin in healthy young subjects: a single-center, multiple-dose, open-label study.

BACKGROUND: The high prevalence rates of both Alzheimer's disease (AD) and type 2 diabetes mellitus in the elderly population suggest that concomitant pharmacotherapy is likely. Given the renal tubular transport and extensive urinary excretion of memantine and metformin, it was of interest to assess the pharmacokinetic and pharmacodynamic interaction with glyburide/metformin. OBJECTIVE: The primary goal of this study was to determine whether an in vivo pharmacokinetic or pharmacodynamic interaction exists between memantine (an uncompetitive, moderate-affinity, N-methyl-D-aspartate receptor antagonist with fast blocking/unblocking kinetics that is available in the United States for moderate to severe AD) and glyburide/metformin (a combination pharmacotherapy formulation approved for glycemic control in patients with type 2 diabetes mellitus). METHODS: In this single-center, multiple-dose, open-label study, healthy adult subjects received a single oral dose of memantine hydrochloride (20 mg) on day 1. After a 14-day washout period, subjects were orally administered 1.25-mg glyburide/250-mg metformin BID with food for 6 days. On day 21, subjects were coadministered memantine (20 mg) and glyburide/metformin with food. Assessments included determination of pharmacokinetic parameters for memantine and the antidiabetic agents when administered alone and in combination, pharmacodynamic measurements of blood glucose levels, and analyses of tolerability. RESULTS: The study population consisted of 24 subjects (13 women, 11 men; 79.2% white) with a mean (SD) age of 26.1 (5.6) years and a mean (SD) weight of 69.5 (11.3) kg. Twenty-one subjects completed the study: 2 discontinued due to adverse events judged unrelated to study medication, and 1 withdrew consent. No significant pharmacokinetic or pharmacodynamic interactions were observed between memantine and glyburide/metformin. Adverse events included dizziness (41.7% of patients) with memantine administration and gastrointestinal effects (nausea, 9.1 %; vomiting, 9.1%; abdominal cramps, 13.6%) with glyburide/metformin administration. CONCLUSIONS: No pharmacokinetic interactions between memantine and glyburide/metformin were detected in this study of healthy young volunteers. Memantine had no effect on the pharmacodynamic activities of glyburide and metformin, and the drug combination was well tolerated in this population.

Adult↗

PubMed1998

Ethanol-reinforced behaviour in the rat: effects of uncompetitive NMDA receptor antagonist, memantine.

Ethanol has been reported to alter NMDA receptor-mediated biochemical and electrophysiological responses in vitro. The aim of the present study was to evaluate the effects of an uncompetitive NMDA receptor antagonist memantine, in animal models of alcoholism. Male Wistar rats were trained to drink 8% ethanol in a free-choice, limited access procedure. A separate group of animals was trained to lever press for 8% ethanol in an operant procedure where ethanol was introduced in the presence of sucrose. The selectivity of memantine's actions was assessed by studying its effects on food or water consumption in separate control experiments. Memantine (4.5-24 mg/kg) significantly, but not dose dependently, affected ethanol drinking in the limited access procedure. However, only 6 mg/kg memantine selectively decreased ethanol drinking. Memantine did not alter ethanol intake in rats trained to lever press for ethanol in the operant procedure. Only 9 mg/kg memantine reduced operant responding in the extinction procedure in the rats trained to lever press for ethanol. The same dose of memantine significantly reduced the operant behaviour of rats trained to respond for water. These results indicate that: (i) single doses of memantine only moderately and not dose dependently reduce alcohol drinking in the limited access procedure; (ii) memantine produces non-selective effects on operant behaviour in rats trained to lever press for ethanol in an oral self-administration procedure.

Alcohol Drinking↗

PubMed1998

Neuroprotective concentrations of the N-methyl-D-aspartate open-channel blocker memantine are effective without cytoplasmic vacuolation following post-ischemic administration and do not block maze learning or long-term potentiation.

The potential of most N-methyl-D-aspartate antagonists as neuroprotectants is limited by side effects. We previously reported that memantine is an open-channel N-methyl-D-aspartate blocker with a faster off-rate than many uncompetitive N-methyl-D-aspartate antagonists such as dizocilpine maleate. This parameter correlated with memantine's known clinical tolerability in humans with Parkinson's disease. Memantine is the only N-methyl-D-aspartate antagonist that has been used clinically for excitotoxic disorders at neuroprotective doses. Therefore, we wanted to investigate further the basis of its clinical efficacy, safety, and tolerability. Here we show for the first time for any clinically-tolerated N-methyl-D-aspartate antagonist that memantine significantly reduces infarct size when administered up to 2 h after induction of hypoxia/ischemia in immature and adult rats. We found that at neuroprotective concentrations memantine results in few adverse side effects. Compared to dizocilpine maleate, memantine displayed virtually no effects on Morris water maze performance or on neuronal vacuolation. At concentrations similar to those in brain following clinical administration, memantine (6-10 microM) did not attenuate long-term potentiation in hippocampal slices and substantially spared the N-methyl-D-aspartate component of excitatory postsynaptic currents, while dizocilpine maleate (6-10 microM) or D-2-amino-5-phosphovalerate (50 microM) completely blocked these phenomena. We suggest that the favorable kinetics of memantine interaction with N-methyl-D-aspartate channels may be partly responsible for its high index of therapeutic safety, and make memantine a candidate drug for use in many N-methyl-D-aspartate receptor-mediated human CNS disorders.

Animals↗