Clinical Trials in Parkinson's Disease Dementia and Dementia with Lewy Bodies

Observational study of quality of life of Parkinson's patients and their caregivers

BACKGROUND

Parkinson's disease (PD) is a degenerative disorder that leads to a decrease in cognitive performance and affects patients' quality of life (QoL). The purpose of this study was to investigate the QoL of PD patients and their caregivers in relation to each patient's cognitive impairment.

METHODS

A total of 60 subjects with idiopathic PD were recruited; all had a primary caregiver. Patients' cognitive abilities were evaluated by the Mini-Mental State Examination, the Activities of Daily Living Scale, and the Instrumental Activities of Daily Living Scale. The 39-item Parkinson's Disease Questionnaire and the 36-item Short Form Health Survey were used to assess the QoL of patients and caregivers, respectively.

RESULTS

The Mini-Mental State Examination was a significant predictor of most of the QoL subscales, including mobility, stigma, social support, cognition, and physical discomfort. The Activities of Daily Living Scale and the Instrumental Activities of Daily Living Scale were significant predictors of mobility, activities of daily living, and cognition. Patients' clinical conditions also significantly affected all of the 36-item Short Form Health Survey subscales; predicted physical functioning, bodily pain, vitality, and social role functioning on the Activities of Daily Living Scale; and predicted physical functioning, physical role functioning, and emotional role functioning on the Mini-Mental State Examination.

CONCLUSIONS

Our results confirm a relationship between PD patients QoL and the perceived burden of their caregivers. Indeed, patients' cognitive impairment strictly correlated to lower QoL scores in both patients and caregivers and is a strong predictor of caregiver stress and burden. These results emphasize the importance of implementing early interventions to prevent or ameliorate caregivers' burnout.

[Treatment of Lewy body dementia]

Lewy body dementia (LBD) is more frequent than previously considered and is characterized by the scarcity of therapeutic resources and the difficulty of treatment since many patients are hypersensitive to neuroleptics. Although further research is required in this field, standardization of the diagnostic criteria has improved the data obtained from research. Currently, anticholinesterase drugs have proven utility in LBD and there is increasing evidence that memantine can also be useful. Typical neuroleptics are dangerous in these patients and should never be used. Among atypical neuroleptics, quetiapine is the best option, although conclusive data are lacking.

Cognitive function as an emerging treatment target for marijuana addiction

Cannabis is the most widely used illicit substance in the world, and demand for effective treatment is increasing. However, abstinence rates following behavioral therapies have been modest, and there are no effective pharmacotherapies for the treatment of cannabis addiction. We propose a novel research agenda and a potential treatment strategy, based on observations that both acute and chronic exposure to cannabis are associated with dose-related cognitive impairments, most consistently in attention, working memory, verbal learning, and memory functions. These impairments are not completely reversible upon cessation of marijuana use, and moreover may interfere with the treatment of marijuana addiction. Therefore, targeting cognitive impairment associated with chronic marijuana use may be a promising novel strategy for the treatment of marijuana addiction. Preclinical studies suggest that medications enhancing the cholinergic transmission may attenuate cannabis-induced cognitive impairments, but these cognitive enhancing medications have not been examined in controlled human studies. Preliminary evidence from individuals addicted to other drugs suggests that computerized cognitive rehabilitation may also have utility to improve cognitive function in marijuana users. Future clinical studies optimally designed to measure cognitive function as well as drug use behavior would be needed to test the efficacy of these treatments for marijuana addiction.

Cognitive enhancement as a pharmacotherapy target for stimulant addiction

BACKGROUND

No medications have been proven to be effective for cocaine and methamphetamine addiction. Attenuation of drug reward has been the main strategy for medications development, but this approach has not led to effective treatments. Thus, there is a need to identify novel treatment targets in addition to the brain reward system.

AIM

To propose a novel treatment strategy for stimulant addiction that will focus on medications enhancing cognitive function and attenuating drug reward.

METHODS

Pre-clinical and clinical literature on potential use of cognitive enhancers for stimulant addiction pharmacotherapy was reviewed.

RESULTS AND CONCLUSIONS

Cocaine and methamphetamine users show significant cognitive impairments, especially in attention, working memory and response inhibition functions. The cognitive impairments seem to be predictive of poor treatment retention and outcome. Medications targeting acetylcholine and norepinephrine are particularly well suited for enhancing cognitive function in stimulant users. Many cholinergic and noradrenergic medications are on the market and have a good safety profile and low abuse potential. These include galantamine, donepezil and rivastigmine (cholinesterase inhibitors), varenicline (partial nicotine agonist), guanfacine (alpha(2)-adrenergic agonist) and atomoxetine (norepinephrine transporter inhibitor). Future clinical studies designed optimally to measure cognitive function as well as drug use behavior would be needed to test the efficacy of these cognitive enhancers for stimulant addiction.

Cholinergic functioning in stimulant addiction: implications for medications development

Acetylcholine, the first neurotransmitter discovered, participates in many CNS functions, including sensory and motor processing, sleep, nociception, mood, stress response, attention, arousal, memory, motivation and reward. These diverse cholinergic effects are mediated by nicotinic- and muscarinic-type cholinergic receptors (nAChR and mAChR, respectively). The goal of this review is to synthesize a growing literature that supports the potential role of acetylcholine as a treatment target for stimulant addiction. Acetylcholine interacts with the dopaminergic reward system in the ventral tegmental area, nucleus accumbens and prefrontal cortex. In the ventral tegmental area, both nAChR and mAChR stimulate the dopaminergic system. In the nucleus accumbens, cholinergic interneurons integrate cortical and subcortical information related to reward. In the prefrontal cortex, the cholinergic system contributes to the cognitive aspects of addiction. Preclinical studies support a facilitative role of nicotinic receptor agonists in the development of stimulant addiction. In contrast, nonselective muscarinic receptor agonists seem to have an inhibitory role. In human studies, acetylcholinesterase inhibitors, which increase synaptic acetylcholine levels, have shown promise for the treatment of stimulant addiction. Further studies testing the efficacy of cholinergic medications for stimulant addiction are warranted.