Dextrometorphan-Paroxetine, But Not Dronabinol, Effective for Treatment-Resistant Aggression and Agitation in an Elderly Patient With Lewy Body Dementia

Targeting Sigma Receptors for the Treatment of Neurodegenerative and Neurodevelopmental Disorders

The sigma-1 receptor is a 223 amino acid-long protein with a recently identified structure. The sigma-2 receptor is a genetically unrelated protein with a similarly shaped binding pocket and acts to influence cellular activities similar to the sigma-1 receptor. Both proteins are highly expressed in neuronal tissues. As such, they have become targets for treating neurological diseases, including Alzheimer's disease (AD), Huntington's disease (HD), Parkinson's disease (PD), multiple sclerosis (MS), Rett syndrome (RS), developmental and epileptic encephalopathies (DEE), and motor neuron disease/amyotrophic lateral sclerosis (MND/ALS). In recent years, there have been many pre-clinical and clinical studies of sigma receptor (1 and 2) ligands for treating neurological disease. Drugs such as blarcamesine, dextromethorphan and pridopidine, which have sigma-1 receptor activity as part of their pharmacological profile, are effective in treating multiple aspects of several neurological diseases. Furthermore, several sigma-2 receptor ligands are under investigation, including CT1812, rivastigmine and SAS0132. This review aims to provide a current and up-to-date analysis of the current clinical and pre-clinical data of drugs with sigma receptor activities for treating neurological disease.

Cannabinoids for the treatment of dementia

BACKGROUND

Dementia is a common chronic condition, mainly affecting older adults, characterised by a progressive decline in cognitive and functional abilities. Medical treatments for dementia are limited. Cannabinoids are being investigated for the treatment of dementia.

OBJECTIVES

To determine the efficacy and safety of cannabinoids for the treatment of dementia.

SEARCH METHODS

We searched ALOIS - the Cochrane Dementia and Cognitive Improvement Group's Specialised Register - on 8 July 2021, using the terms cannabis or cannabinoid or endocannabinoid or cannabidiol or THC or CBD or dronabinol or delta-9-tetrahydrocannabinol or marijuana or marihuana or hashish. The register contains records from all major healthcare databases (the Cochrane Library, MEDLINE, Embase, PsycINFO, CINAHL, LILACS), as well as from many clinical trials registries and grey literature sources.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) of cannabinoids for the treatment of dementia. We included participants of any age and of either sex with diagnosed dementia of any subtype, or with unspecified dementia of any severity, from any setting. We considered studies of cannabinoids administered by any route, at any dose, for any duration, compared with placebo, no treatment, or any active control intervention.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened and selected studies for inclusion, extracted data, and assessed the risk of bias in included studies. When necessary, other review authors were involved in reaching consensus decisions. We conducted meta-analyses using a generic inverse variance fixed-effect model to derive estimates of effect size. We used GRADE methods to assess our confidence in the effect estimates.

MAIN RESULTS

We included four studies (126 participants) in this review. Most participants had Alzheimer's disease; a few had vascular dementia or mixed dementia. Three studies had low risk of bias across all domains; one study had unclear risk of bias for the majority of domains.  The included studies tested natural delta-9-tetrahydrocannabinol (THC) (Namisol) and two types of synthetic THC analogue (dronabinol and nabilone). Three trials had a cross-over design. Interventions were applied over 3 to 14 weeks; one study reported adverse events over 70 weeks of follow-up. One trial was undertaken in the USA, one in Canada, and two in The Netherlands. Two studies reported non-commercial funding, and two studies were conducted with the support of both commercial and non-commercial funding. Primary outcomes in this review were changes in global and specific cognitive function, overall behavioural and psychological symptoms of dementia (BPSD), and adverse events. We found very low-certainty evidence suggesting there may be little or no clinically important effect of a synthetic THC analogue on cognition assessed with the standardised Mini-Mental State Examination (sMMSE) (mean difference (MD) 1.1 points, 95% confidence interval (CI) 0.1 to 2.1; 1 cross-over trial, 28 participants).  We found low-certainty evidence suggesting there may be little or no clinically important effect of cannabinoids on overall behavioural and psychological symptoms of dementia assessed with the Neuropsychiatric Inventory (or its modified nursing home version) (MD -1.97, 95% CI -3.87 to -0.07; 1 parallel group and 2 cross-over studies, 110 participants). All included studies reported data on adverse events. However, the total number of adverse events, the total numbers of mild and moderate adverse events, and the total number of serious adverse events (SAEs) were not reported in a way that permitted meta-analysis.  There were no clear differences between groups in numbers of adverse events, with the exception of sedation (including lethargy), which was more frequent among participants taking nabilone (N = 17) than placebo (N = 6) (odds ratio (OR) 2.83, 95% CI 1.07 to 7.48; 1 cross-over study, 38 participants). We judged the certainty of evidence for adverse event outcomes to be low or very low due to serious concerns regarding imprecision and indirectness.

AUTHORS' CONCLUSIONS

Based on data from four small, short, and heterogeneous placebo-controlled trials, we cannot be certain whether cannabinoids have any beneficial or harmful effects on dementia. If there are benefits of cannabinoids for people with dementia, the effects may be too small to be clinically meaningful. Adequately powered, methodologically robust trials with longer follow-up are needed to properly assess the effects of cannabinoids in dementia.

Effectiveness of Cannabinoids for Treatment of Dementia: A Systematic Review of Randomized Controlled Trials

Objective: In the last decade, research has focused on developing novel medications for the treatment of dementia. Cannabinoids are one of the potential agents under investigation. The present study aimed to examine the evidence concerning the effectiveness of cannabinoids for the treatment of dementia. Methods: We undertook a systematic review complying to PRISMA guidelines. Four databases were searched including Medline, Embase, Cochrane Library, and PsychINFO. Results: Five studies evaluated the use of cannabinoids for anorexia and agitation in dementia. One study used dronabinol 5 mg/day to target anorexic symptoms of dementia which positively impacted on weight. Results of two trials investigating the effectiveness of tetrahydrocannabinol (THC) 1.5-4.5 mg/day for the treatment of agitation indicated no significant differences between THC and placebo. The most recent trial reported significant improvement in agitation using nabilone at 1-2 mg/day. However, levels of evidence of these agents were rated as low and very low because of low sample size and methodology issues. No studies were available that investigated the use of cannabinoids to moderate cognitive symptoms in dementia. Conclusions: Findings from a few robust randomized controlled trials suggest that nabilone might be useful for the treatment of agitation in patients with dementia, but there is no convincing evidence for THC. Additional studies are needed to further clarify and assess the benefits of these treatments. Clinical Implications: There were no randomized controlled trials investigating the use of cannabinoids for the treatment of cognitive decline in dementia. Studies on THC reported no significant improvement in agitation. It may be too early to postulate that cannabinoids have any effect on dementia symptoms or their progression.