Can Amantadine Ameliorate Neurocognitive Functions After Subarachnoid Haemorrhage? A Preliminary Study

Significance of NMDA receptor-targeting compounds in neuropsychological disorders: An In-depth Review

N-methyl-D-aspartate receptors (NMDARs), a subclass of glutamate-gated ion channels, play an integral role in the maintenance of synaptic plasticity and excitation-inhibition balance within the central nervous system (CNS). Any irregularities in NMDAR functions, whether hypo-activation or over-activation, can destabilize neural networks and impair CNS function. Several decades of experimental and clinical investigations have demonstrated that NMDAR dysfunction is implicated in the pathophysiology of various neurological disorders. Despite designing a long list of compounds that differentially modulate NMDARs, success in developing drugs that can selectively and effectively regulate various NMDAR subtypes while showing encouraging efficacy in clinical settings remains limited. A better understanding of the basic mechanism of NMDAR function, particularly its selective regulation in pathological conditions, could aid in designing effective drugs for the treatment of neurological conditions. Here, we reviewed the experimental and clinical investigations that studied the effects of available NMDAR modulators in various neurological disorders and weighed up the pros and cons of the use of these substances on the improvement of functional outcomes of these disorders. Despite numerous efforts to develop NMDAR modulatory drugs that did not produce the desired outcomes, NMDARs remain a significant target for advancing novel drugs to treat neurological disorders. This article reviews the complexity of NMDAR signaling dysfunction in different neurological diseases, the efforts taken to examine designed compounds targeting specific subtypes of NMDARs, including challenges accompanied by using these substances, and the potential enhancements in drug discovery for NMDAR modulatory compounds by innovative technologies.

Neurostimulant Use for Rehabilitation and Recovery After Stroke: A Narrative Literature Review

BACKGROUND

Stroke often results in significant impairments across various domains, including movement, language, cognition, and mood. Neurostimulants have been proposed as potential therapeutic interventions to enhance recovery in these areas.

METHODS

This narrative literature review examines clinical trials investigating the efficacy of neurostimulants in poststroke recovery. It evaluates outcomes related to aphasia, motor deficits, cognition, fatigue, and depression.

RESULTS

The qualitative analysis included 34 trials testing the following neurostimulants: methylphenidate (n=6), amphetamines (n=8), memantine (n=2), modafinil (n=2), levodopa (n=14), amantadine (n=1), bromocriptine (n=3), and ropinirole (n=1). Of the 34 studies, 31 were randomized, placebo-controlled (double-blind, n=27; single-blind, n=2; unblinded n=2), 2 were randomized and not placebo-controlled, and 1 was not randomized. Study design was either multiarm (n=23), crossover (n=10), or used subjects as their own control (n=1). Mean sample size was 49.4 (5-593).

CONCLUSIONS

Current evidence suggests that memantine may be effective for aphasia, although few phase III trials exist, whereas bromocriptine and amphetamines lack sufficient evidence for long-term recovery of aphasia. Levodopa may improve motor aphasias but has not shown long-term benefits for motor recovery. Similarly, ropinirole has not been shown to improve poststroke motor outcomes. Methylphenidate has limited efficacy for cognitive improvement but may enhance poststroke functionality and mood. Modafinil may help with poststroke fatigue. In conclusion, there are promising results of positive effects of neurostimulants with few side effects, though studies are limited by heterogeneous designs and small sample sizes. Neurostimulant efficacy must be assessed in conjunction with specific rehabilitation modalities as part of larger, well-designed studies to best understand their effects on impairment.

The impact of sleep problems on cerebral aneurysm risk is mediated by hypertension: a mediated Mendelian randomization study

Introduction

Cerebral aneurysm (CA) is a common vascular disease. The risk factors of CA include hypertension, smoking, and a family history of genetic predisposition. Although sleep-related problems have been found to have a strong association with cardiovascular disease, there is a lack of research regarding the causal relationship with cerebral aneurysms.

Methods

In this study, we investigated the causal relationship between four sleep-related problems, including snoring, insomnia, narcolepsy, and napping during the day, and CA using a two-sample Mendelian randomization (MR) analysis. Moreover, the potential confounders before sleep problems and CA were further analyzed by multivariate MR (MVMR).

Results

The causal relationship between insomnia and CA was obtained analytically by means of six MR analyses. There was a strong causal effect relationship between insomnia and CA, which suggests this as a potential risk factor [odds ratio (OR) = 8.35, 95% confidence interval (CI) = 2.422-28.791, p = 7.772e-04]. On this basis, hypertension was identified as a mediator between insomnia and CA by MVMR, with a mediating effect of 52.538% (OR = 3.05, 95% CI = 1.549-4.55, p = 0.015).

Conclusion

The causal relationship between insomnia and CA was predicted using genetic variance data, and insomnia was found to be a potential risk factor. Furthermore, hypertension is a mediator between insomnia and CA. Therefore, focusing on sleep problems and improving sleep quality may be an active and effective strategy to prevent CA.

Informing future randomized controlled trials of amantadine hydrochloride in neurocritical care and post-neurocritical care stroke patients through a retrospective study

BACKGROUND

Amantadine hydrochloride has been increasingly prescribed as a neurostimulant for neurocritical care stroke patients to promote wakefulness during inpatient recovery. However, a lack of guidelines makes it difficult to decide who may benefit from this pharmacotherapy and when amantadine should be initiated during the hospital stay. This study aims to determine some factors that may be associated with favorable response to amantadine to inform future randomized controlled trials of amantadine in critical care or post-critical care stroke patients.

METHODS

Retrospective chart review for this study included neurocritical care and post-neurocritical care patients with acute ischemic or hemorrhagic stroke who were started on amantadine (N = 34) in the years 2016-2019. Patients were labeled as either responders or nonresponders of amantadine within 9 days of initiation using novel amantadine scoring criteria utilized and published in Neurocritical Care in the year 2021, which included spontaneous wakefulness and Glasgow Coma Scale (GCS). Amantadine response status and predictive variables were analyzed using nonparametric tests and adjusted multivariable regression models.

RESULTS

There were large but nonsignificant variations in the median total milligrams of amantadine received in the first 9 days (IQR = 700-1,450 mg, p = 0.727). GCS on the day before amantadine initiation was significantly higher for responders (median = 12, IQR = 9-14) than nonresponders (median = 9, IQR = 8-10, p = 0.009). Favorable responder status was significantly associated with initiation in the critical care unit versus the step-down unit or the general medical/surgical floor [𝛃=1.02, 95% CI (0.10, 1.93), p = 0.031], but there was no significant associations with hospital day number started [𝛃=-0.003, 95% CI (-0.02, 0.02), p = 0.772].

CONCLUSIONS

Future randomized controlled trials of amantadine in hospitalized stroke patients should possibly consider examining dose-dependent relationships to establish stroke-specific dosing guidelines, minimum GCS threshold for which amantadine is efficacious, and the impact of patients' determined level of acuity on clinical outcomes instead of solely examining the impact of earlier amantadine initiation by hospital day number. Future research with larger sample sizes is needed to further examine these relationships and inform future clinical trials.

Does amantadine improve cognitive recovery in severe disorders of consciousness after aneurysmal subarachnoid hemorrhage? A double-blind placebo-controlled study

BACKGROUND

Severe disorders of consciousness (sDoC) are a common sequela of aneurysmal subarachnoid hemorrhages (aSAH), and amantadine has been used to improve cognitive recovery after traumatic brain injury.

OBJECTIVE

This study evaluated the effect of amantadine treatment on consciousness in patients with sDoC secondary to aSAH.

METHODS

This double-center, randomized, prospective, cohort study included patients ≥ 18 years old with sDoC after aSAH from February 2020 to September 2023. Individual patient data of patients were pooled to determine the effect of amantadine, in comparison to placebo. The primary outcomes at 3 and 6 months after the ictus were evaluated using the modified Rankin scale (mRS) and Glasgow outcome scale (GOS). In addition to all-cause mortality, secondary endpoints were assessed weekly during intervention by scores on Rappaport's Disability Rating Scale (RDRS) and Coma Recovery Scale-Revised (CRSR).

RESULTS

Overall, 37 patients with sDoC and initial Glasgow Coma Scale (GCS) varying between 3 and 11 were recruited and randomized to amantadine (test group, n = 20) or placebo (control group, n = 17). The average age was 59.5 years (28 to 81 year-old), 24 (65%) were women, and the mean GCS at the beginning of intervention was 7.1. Most patients evolved to vasospasm (81%), with ischemia in 73% of them. The intervention was started between 30 to 180 days after the ictus, and administered for 6 weeks, with progressively higher doses. Neither epidemiological characteristics nor considerations regarding the treatment of the aneurysm and its complications differed between both arms. Overall mortality was 10.8% (4 deaths). During the study, four patients had potential adverse drug effects: two presented seizures, one had paralytic ileus, and another evolved with tachycardia; the medication was not suspended, only the dose was not increased. At data opening, 2 were taking amantadine and 2 placebo.

CONCLUSION

Despite some good results associated with amantadine in the literature, this study did not find statistically significant positive effects in cognitive recovery in patients with delayed post-aSAH sDoC. Further large randomized clinical trials in patients' subgroups are needed to better define its effectiveness and clarify any therapeutic window where it can be advantageous.

Amantadine treatment is associated with improved consciousness in patients with non-traumatic brain injury

OBJECTIVE

This study determined the effect of amantadine treatment on consciousness in patients with non-traumatic brain injury.

METHODS

We pooled individual patient data of five single-centre observational studies to determine the effect of amantadine treatment among patients with ischaemic stroke, intracerebral haemorrhage, subarachnoid haemorrhage, community-acquired bacterial meningitis and status epilepticus, admitted between January 2012 and December 2015 and ventilated ≥7 days. Patient selection and multivariable regression modelling were used to adjust for differences in intergroup comparison and for parameters associated with consciousness. Improvement of consciousness 5 days after treatment initiation was defined as primary outcome. Secondary outcomes included Glasgow Coma Scale (GCS) at day 5 and GCS at day 10, rate of ICU delirium, epileptic seizures and all-cause mortality at 90 days.

RESULTS

Overall, 84 of 294 (28.6%) eligible patients received amantadine. Amantadine treatment was associated with improvement of consciousness at day 5 (amantadine: 86.9% vs control: 54.0%; absolute difference: 32.9 (20.0-44.2); adjusted OR (aOR): 5.71 (2.50-13.05), p<0.001). Secondary outcomes showed differences in GCS 5 days (9 (8-11) vs 6 (3-9), p<0.001) and GCS 10 days (10(8-11) vs 9(6-11),p=0.003) after treatment initiation. There were no significant differences regarding all-cause mortality (aOR: 0.89 (0.44-1.82), p=0.758) and ICU delirium (aOR: 1.39 (0.58-3.31), p=0.462). Rate of epileptic seizures after initiation of amantadine treatment was numerically higher in the amantadine group (amantadine: 10.7% vs control: 3.0%; absolute difference: 7.7 (0.3-16.4); aOR: 3.68 (0.86-15.71), p=0.079).

CONCLUSIONS

Amantadine treatment is associated with improved consciousness among patients with different types of non-traumatic brain injury in this observational cohort analysis. Epileptic seizures should be considered as potential side effects and randomised controlled trials are needed to confirm these findings.

Amantadine and Modafinil as Neurostimulants During Post-stroke Care: A Systematic Review

Amantadine and modafinil are neurostimulants that may improve cognitive and functional recovery post-stroke, but the existing study results vary, and no comprehensive review has been published. This systematic review describes amantadine and modafinil administration practices post-stroke, evaluates timing and impact on clinical effectiveness measures, and identifies the incidence of potential adverse drug effects. A librarian-assisted search of the MEDLINE (PubMed) and EMBASE databases identified all English-language publications with "amantadine" or "modafinil" in the title or abstract from inception through February 1, 2020. Publications meeting predefined Patient, Intervention, Comparator, Outcome (PICO) criteria were included: Patients (≥ 18 years of age post-stroke); Intervention (amantadine or modafinil administration); Comparison (pretreatment baseline or control group); Outcomes (cognitive or functional outcome). Amantadine and modafinil administration practices, cognitive and functional outcomes, and incidence of potential adverse drug effects were collected following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidance. Quantitative analyses were not performed due to heterogeneity in the clinical effectiveness measures; descriptive data are presented as number (percent) or median (interquartile range). Of 12,620 publications initially identified, 10 amantadine publications (n = 121 patients) and 12 modafinil publications (n = 120 patients) were included. Amantadine was initiated 39 (16, 385) days post-stroke, with most common initial doses of 100 mg once or twice daily (range 100-200 mg/day), and final daily dose of 200 (188, 200) mg/day. Modafinil was initiated 170 (17, 496) days post-stroke, with initial and final daily doses of 100 (100, 350) mg/day and 200 (100, 350) mg/day, respectively. The most common indication was consciousness disorders for amantadine (n = 3/10 publications; 30%) and fatigue for modafinil (n = 5/12; 42%). Forty unique clinical effectiveness measures (1.8 per study) with 141 domains (6.4 per study) were described across all studies. A positive response in at least one clinical effectiveness measure was reported in 70% of amantadine publications and 83% of modafinil publications. Only one publication each for amantadine (10%; n = 5 patients) and modafinil (8%; n = 21 patients) studied acutely hospitalized or ICU patients; both were randomized studies showing improvements in neurocognitive function for amantadine and fatigue for modafinil. Potential adverse drug effects were reported in approximately 50% of publications, most commonly visual hallucinations with amantadine (2% of patients) and dizziness (5% of patients) and dry eyes or mouth (5% of patients). Amantadine and modafinil may improve cognitive and functional recovery post-stroke, but higher-quality data are needed to confirm this conclusion, especially in the acute care setting.

Amantadine: reappraisal of the timeless diamond-target updates and novel therapeutic potentials

The aim of the current review was to provide a new, in-depth insight into possible pharmacological targets of amantadine to pave the way to extending its therapeutic use to further indications beyond Parkinson's disease symptoms and viral infections. Considering amantadine's affinities in vitro and the expected concentration at targets at therapeutic doses in humans, the following primary targets seem to be most plausible: aromatic amino acids decarboxylase, glial-cell derived neurotrophic factor, sigma-1 receptors, phosphodiesterases, and nicotinic receptors. Further three targets could play a role to a lesser extent: NMDA receptors, 5-HT3 receptors, and potassium channels. Based on published clinical studies, traumatic brain injury, fatigue [e.g., in multiple sclerosis (MS)], and chorea in Huntington's disease should be regarded potential, encouraging indications. Preclinical investigations suggest amantadine's therapeutic potential in several further indications such as: depression, recovery after spinal cord injury, neuroprotection in MS, and cutaneous pain. Query in the database http://www.clinicaltrials.gov reveals research interest in several further indications: cancer, autism, cocaine abuse, MS, diabetes, attention deficit-hyperactivity disorder, obesity, and schizophrenia.

Amantadine and Modafinil as Neurostimulants Following Acute Stroke: A Retrospective Study of Intensive Care Unit Patients

Background/Objective

Neurostimulants may improve or accelerate cognitive and functional recovery after intracerebral hemorrhage (ICH), ischemic stroke (IS), or subarachnoid hemorrhage (SAH), but few studies have described their safety and effectiveness in the intensive care unit (ICU). The objective of this study was to describe amantadine and modafinil administration practices during acute stroke care starting in the ICU and to evaluate safety and effectiveness.

Methods

Consecutive adult ICU patients treated with amantadine and/or modafinil following acute non-traumatic IS, ICH, or SAH were evaluated. Neurostimulant administration data were extracted from the electronic medication administration record, including medication (amantadine, modafinil, or both), starting dose, time from stroke to initiation, and whether the neurostimulant was continued at hospital discharge. Patients were considered responders if they met two of three criteria within 9 days of neurostimulant initiation: increase in Glasgow coma scale (GCS) score ≥ 3 points from pre-treatment baseline, improved wakefulness or participation documented in caregiver notes, or clinical improvement documented in physical or occupational therapy notes. Potential confounders of the effectiveness assessment and adverse drug effects were also recorded.

Results

A total of 87 patients were evaluable during the 3.7-year study period, including 41 (47%) with ICH, 29 (33%) with IS, and 17 (20%) with SAH. The initial neurostimulant administered was amantadine in 71 (82%) patients, modafinil in 13 (15%), or both in 3 (3%) patients. Neurostimulants were initiated a median of 7 (4.25, 12.75) days post-stroke (range 1–27 days) for somnolence (77%), not following commands (32%), lack of eye opening (28%), or low GCS (17%). The most common starting dose was 100 mg twice daily for both amantadine (86%) and modafinil (54%). Of the 79 patients included in the effectiveness evaluation, 42 (53%) were considered responders, including 34/62 (55%) receiving amantadine monotherapy and 8/24 (33%) receiving both amantadine and modafinil at the time they met the definition of a responder. No patient receiving modafinil monotherapy was considered a responder. The median time from initiation to response was 3 (2, 5) days. Responders were more frequently discharged home or to acute rehabilitation compared to non-responders (90% vs 62%, p = 0.006). Among survivors, 63/72 (88%) were prescribed a neurostimulant at hospital discharge. The most common potential adverse drug effect was sleep disruption (16%).

Conclusions

Neurostimulant administration during acute stroke care may improve wakefulness. Future controlled studies with a neurostimulant administration protocol, prospective evaluation, and discretely defined response and safety criteria are needed to confirm these encouraging findings.

Electronic supplementary material

The online version of this article (10.1007/s12028-020-00986-4) contains supplementary material, which is available to authorized users.

Amantadine and memantine: a comprehensive review for acquired brain injury

This comprehensive review discusses clinical studies of patients following brain injuries (traumatic, acquired, or stroke), who have been treated with amantadine or memantine. Both amantadine and memantine are commonly used in the acute rehabilitation setting following brain injuries, despite their lack of FDA-approval for neuro-recovery. Given the broad utilization of such agents, there is a need to review the evidence supporting this common off-label prescribing. The purpose of this review is to describe the mechanisms of action for memantine and amantadine, as well as to complete a comprehensive review of the clinical uses of these agents. We included 119 original, clinical research articles from NCBI Medline, published before 2019. We focused on the domains of neuroplasticity, functional recovery, motor recovery, arousal, fatigue, insomnia, behavior, agitation, and cognition. Most of the existing research supporting the use of amantadine and memantine in recovery from brain injuries was done in very small populations, limiting the significance of conclusions. While most studies are positive; small effect sizes are usually reported, or populations are subject to bias. Furthermore, evidence is so limited that this review includes research regarding both acute and chronic acquired brain injury populations. Fortunately, reported short-term side effects generally are modest, and stop soon after amantadine/memantine is discontinued. However, responses are inconsistent, and the phenotype of responders remains elusive.