Effect of donepezil added to atypical antipsychotics on cognition in patients with schizophrenia: an open-label trial

Cholinergic Functioning, Cognition, and Anticholinergic Medication Burden in Schizophrenia

Acetylcholine (ACh) signaling is critical for central nervous function and is known to be abnormal in schizophrenia (SZ), a chronic neuropsychiatric disorder in which cognitive deficits persist, despite treatment. This review provides a summary of the clinical evidence linking ACh abnormalities to SZ-associated cognitive deficits, an overview of ACh-based pro-cognitive strategies attempted in SZ, and a survey of recent studies that describe the impact of anticholinergic medication burden on cognitive outcomes in SZ. Methodological challenges that currently limit more substantial investigation of ACh in SZ patients and future directions are also discussed.

The effects of donepezil on phencyclidine-induced cognitive deficits in a mouse model of schizophrenia

Donepezil is the first-line of treatment for Alzheimer's disease (AD), which improves cognitive impairment effectively, but whether it has an impact on cognitive impairment in schizophrenia remains unknown. In this study, we evaluated the effects and mechanisms of donepezil on schizophrenia-like cognitive deficits induced by phencyclidine (PCP). The cognitive deficits model of schizophrenia was established by injecting PCP into mice. Risperidone, an atypical antipsychotic drug, served as positive control drug. Three behavioral tests including novel object recognition (NOR) test, Morris Water Maze (MWM) and passive avoidance (PA) test were performed to evaluate the effect of donepezil on PCP-induced cognitive deficits. Furthermore, the content of BDNF and NGF in the hippocampus and cortex of mice was determined using ELISA. Expressions of p-GSK-3β/GSK-3β, p-Akt/Akt, Bcl-2/Bax and Caspase-3 in the hippocampus and cortex were detected by Western blot. Results revealed that donepezil has a protective effect on PCP-induced cognitive dysfunction. Moreover, donepezil can also improve PCP-induced schizophrenia-like cognitive deficits by inhibiting neuronal apoptosis and regulating synaptic plasticity, which was possible through the up-regulation of p-Akt, p-GSK-3β, Bcl-2 and the down-regulation of Bax, Caspase-3. The results indicated that donepezil might exhibit a beneficial effect on the treatment of cognitive dysfunction in schizophrenia.

Medications Used for Cognitive Enhancement in Patients With Schizophrenia, Bipolar Disorder, Alzheimer's Disease, and Parkinson's Disease

BACKGROUND/AIMS

Cognitive impairment, which frequently occurs in patients with schizophrenia, bipolar disorder, Alzheimer's disease, and Parkinson's disease, has a significant impact on the daily lives of both patients and their family. Furthermore, since the medications used for cognitive enhancement have limited efficacy, the issue of cognitive enhancement still remains a clinically unsolved challenge.

SAMPLING AND METHODS

We reviewed the clinical studies (published between 2007 and 2017) that focused on the efficacy of medications used for enhancing cognition in patients with schizophrenia, bipolar disorder, Alzheimer's disease, and Parkinson's disease.

RESULTS

Acetylcholinesterase inhibitors and memantine are the standard treatments for Alzheimer's disease and Parkinson's disease. Some studies have reported selective cognitive improvement in patients with schizophrenia following galantamine treatment. Newer antipsychotics, including paliperidone, lurasidone, aripiprazole, ziprasidone, and BL-1020, have also been reported to exert cognitive benefits in patients with schizophrenia. Dopaminergic medications were found to improve language function in patients with Parkinson's disease. However, no beneficial effects on cognitive function were observed with dopamine agonists in patients with schizophrenia. The efficacies of nicotine and its receptor modulators in cognitive improvement remain controversial, with the majority of studies showing that varenicline significantly improved the cognitive function in schizophrenic patients. Several studies have reported that N-methyl-d-aspartate glutamate receptor (NMDAR) enhancers improved the cognitive function in patients with chronic schizophrenia. NMDAR enhancers might also have cognitive benefits in patients with Alzheimer's disease or Parkinson's disease. Raloxifene, a selective estrogen receptor modulator, has also been demonstrated to have beneficial effects on attention, processing speed, and memory in female patients with schizophrenia.

CONCLUSION

Clinical trials with larger sample sizes evaluating comprehensive cognitive domains are warranted to examine the efficacy of medications in cognitive enhancement in patients with schizophrenia, bipolar disorder, Alzheimer's disease, and Parkinson's disease.

Agomelatine as a Treatment for Attention-Deficit/Hyperactivity Disorder in Children and Adolescents: A Double-Blind, Randomized Clinical Trial

OBJECTIVE

Attention-deficit/hyperactivity disorder (ADHD) is a chronic neurodevelopmental disorder. Due to lack of response to the medication and significant side effects of the treatment with stimulants, alternative medications should be considered. The aim of this study is to evaluate efficacy of agomelatine in treatment of ADHD.

METHODS

Fifty-four outpatients, children 6-15 years old, with diagnosis of ADHD according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) diagnostic criteria participated in a 6-week, parallel, double-blind, randomized clinical trial. Fifty patients completed 6 weeks of treatment with either ritalin (methylphenidate hydrochloride [MPH]) (20 mg/day in participants below 30 kg and 30 mg/day in patients with weight ≥30 kg) or agomelatine (15 mg/day in patients with weight ≥30 kg and 25 mg/day in patients with weight ≥45 kg). Participants were assessed using Parent and Teacher ADHD Rating Scale-IV at baseline and at weeks 3 and 6.

RESULTS

General linear model repeated measures showed no significant differences between the two groups on Parent and Teacher Rating Scale scores (F = 1.13, df = 1.26, p = 0.305, and F = 0.95, df = 1.25, p = 0.353, respectively). Changes in Teacher and Parent ADHD Rating Scale scores from baseline to the study end were not significantly different between the agomelatine group (9.28 ± 8.72 and 24.12 ± 7.04, respectively) and the MPH group (6.64 ± 11.04 and 25.76 ± 7.82, respectively) (p = 0.46 and p = 0.44, respectively). There was a trend for less insomnia in the agomelatine group versus MPH-treated group (4% vs. 24%, p = 0.09).

CONCLUSIONS

A treatment course of 6 weeks with agomelatine demonstrated a favorable safety and efficacy profile in children and adolescents with ADHD. Nonetheless, larger controlled studies with longer treatment periods are necessary.

Psychopharmacological treatment of neurocognitive deficits in people with schizophrenia: a review of old and new targets

Neurocognitive impairments significantly contribute to disability and the overall clinical picture in schizophrenia spectrum disorders. There has therefore been a concerted effort, guided by the discovery of neurotransmitter and synaptic systems in the central nervous system, to develop and test compounds that may ameliorate neurocognitive deficits. The current article summarizes the results of efforts to test neurocognitive-enhancing agents in schizophrenia. Overall, existing clinical trials provide little reason to be enthusiastic about the benefits of psychopharmacological agents at enhancing neurocognition in schizophrenia-a state of affairs that may reflect the inadequacy of single neurotransmitter or receptor models. The etiologic and phenomenological complexity of neurocognitive deficits in schizophrenia may be better served by psychopharmacological agents that (i) target neurotransmitter systems proximal in the causal chain to neurocognitive deficits; (ii) enhance distal survival processes in the central nervous system-neurogenesis, neuronal growth, synaptogenesis, and connectivity; and (iii) counteract the negative effects of aberrant neurodevelopment in schizophrenia, such as neuroinflammation and oxidative stress. Future efforts to develop psychopharmacological agents for neurocognitive impairment in schizophrenia should reflect the knowledge of its complex etiology by addressing aberrations along its causal chain. Clinical trials may benefit methodologically from (i) an appreciation of the phenomenological heterogeneity of neurocognitive deficits in schizophrenia; (ii) a characterization of the predictors of treatment response; and (iii) a recognition of issues of sample size, statistical power, treatment duration, and dosing.

Spontaneous object recognition and its relevance to schizophrenia: a review of findings from pharmacological, genetic, lesion and developmental rodent models

RATIONALE

Spontaneous (novel) object recognition (SOR) is one of the most widely used rodent behavioural tests. The opportunity for rapid data collection has made SOR a popular choice in studies that explore cognitive impairment in rodent models of schizophrenia, and that test the efficacy of drugs intended to reverse these deficits.

OBJECTIVES

We provide an overview of the many recent studies that have used SOR to explore the mnemonic effects of manipulation of the key transmitter systems relevant to schizophrenia-the dopamine, glutamate, GABA, acetylcholine, serotonin and cannabinoid systems-alone or in combination. We also review the use of SOR in studying memory in genetically modified mouse models of schizophrenia, as well as in neurodevelopmental and lesion models. We end by discussing the construct and predictive validity, and translational relevance, of SOR with respect to cognitive impairment in schizophrenia.

RESULTS

Perturbation of the dopamine or glutamate systems can generate robust and reliable impairment in SOR. Impaired performance is also seen following antagonism of the muscarinic acetylcholine system, or exposure to cannabinoid agonists. Cognitive enhancement has been reported using alpha7-nicotinic acetylcholine receptor agonists and 5-HT(6) antagonists. Among non-pharmacological models, neonatal ventral hippocampal lesions and maternal immune activation can impair SOR, while mixed results have been obtained with mice carrying mutations in schizophrenia risk-associated genes, including neuregulin and COMT.

CONCLUSIONS

While SOR is not without its limitations, the task represents a useful method for studying manipulations with relevance to cognitive impairment in schizophrenia, as well as the interactions between them.

Phencyclidine withdrawal disrupts episodic-like memory in rats: reversal by donepezil but not clozapine

Episodic memory is the capacity to recall an event in time and place (What? Where? When?). Impaired episodic memory is a debilitating cognitive symptom in schizophrenia but is poorly controlled by currently available antipsychotic drugs. Consistent with glutamatergic abnormality in schizophrenia, the NDMA receptor antagonist, phencyclidine (PCP), induces persistent 'schizophrenia-like' symptoms including memory deficits in humans and rodents and is widely used as an animal model of the disorder. However, in contrast to humans, PCP and PCP withdrawal-induced memory deficits in rodents are reversed by antipsychotic drugs such as clozapine. One possible explanation is that the memory tasks used in animal studies do not simultaneously test the What? Where? When? components that characterize episodic memory in human tasks. We investigated whether subchronic PCP withdrawal disrupts memory in rats in a task that requires simultaneous integration of memory for object, place and context. Rats learn to discriminate objects under specific spatial and contextual conditions analogous to the What? Where? When? components of human episodic memory. We found that PCP withdrawal impaired performance on this task and that the atypical antipsychotic drug clozapine did not reverse this impairment. However the acetylcholinesterase inhibitor (AChEI) donepezil, which has been shown to improve episodic memory in humans did reverse the effect of PCP. This suggests that PCP withdrawal disruption of object-place-context recognition in rats may prove to be a useful model to investigate episodic memory impairment in schizophrenia and supports the suggestion that AChEIs could prove to be a useful pharmacological strategy to specifically treat episodic memory problems in schizophrenia.

Polypharmacy in schizophrenia

PURPOSE OF REVIEW

Although most guidelines recommend monotherapy in schizophrenia, the combined application of multiple psychotropic agents is very common, especially in treatment-refractory cases. We review the empirical basis supporting these attempts and their relevance for clinical practice.

RECENT FINDINGS

Polypharmacy intends to address different aspects of treatment resistance, most importantly insufficient response of psychotic positive and negative symptoms, but also cognitive disturbances, affective comorbidity, obsessive-compulsive syndromes and side-effects of antipsychotic drugs. This review summarizes the current state of evidence of combined antipsychotic treatment strategies and the augmentation of antipsychotics with mood stabilizers, antidepressants and experimental substances.

SUMMARY

In general, rigorous data on combination therapy in schizophrenia are rare and further randomized controlled trials, naturalistic trials and head-to-head-trials are necessary. Some evidence supports a combination of antipsychotics and antidepressants for negative symptoms and comorbid major depressive episodes. The add-on of lithium and mood stabilizers lacks compelling evidence, but might be beneficial for specific subgroups. For treatment-resistant cognitive symptoms, antipsychotic medication should be combined with cognitive remediation, as no pharmacological add-on strategy has gained convincing evidence so far. Treatment-emergent positive and/or negative symptoms under clozapine monotherapy might benefit from adding a second atypical substance.

Pharmacological strategies for enhancing cognition in schizophrenia

Researchers have long recognized that individuals with schizophrenia experience challenges in a wide range of cognitive domains, and research on cognitive impairment in schizophrenia is not a recent phenomena. However, the past 10-20 years have seen an increasing recognition of the central importance of cognition to understanding function and outcome in this illness (Green et al. in Schizophr Bull 26:119-136, 2000), an awareness that has shifted the emphasis of at least some work on schizophrenia. More specifically, there has been a rapidly growing body of work on methods of enhancing cognition in schizophrenia, as a means to potentially facilitate improved outcome and quality of life for individuals with this debilitating illness. The current chapter reviews the results of a range of studies examining adjunctive pharmacological treatments to enhance cognition in schizophrenia using a range of designs, including single-dose studies, open-label repeated dosing studies, and double-blind parallel group and crossover designs with repeated dosing. Although many of the single-dose and open-label studies have suggested positive cognitive effects from a range of agents, few of the larger-scale double-blind studies have generated positive results. The current state of results may reflect the need to identify alternative molecular mechanisms for enhancing cognition in schizophrenia or the need to reconceptualize the ways in which pharmacological agents may improve cognition in this illness, with a concomitant change in the traditional clinical trial study design used in prior studies of cognitive enhancement in schizophrenia.

Translational Aspects of the Novel Object Recognition Task in Rats Abstinent Following Sub-Chronic Treatment with Phencyclidine (PCP): Effects of Modafinil and Relevance to Cognitive Deficits in Schizophrenia

Phencyclidine (PCP) induces a behavioral syndrome in rodents that bears remarkable similarities to some of the core symptoms observed in schizophrenic patients, among those cognitive deficits. The successful alleviation of cognitive impairments associated with schizophrenia (CIAS) has become a major focus of research efforts as they remain largely untreated. The aim of the present study was to investigate the effects of selected antipsychotic and cognition enhancing drugs, namely haloperidol, risperidone, donepezil, and modafinil in an animal model widely used in preclinical schizophrenia research. To this end, the novel object recognition (NOR) task was applied to rats abstinent following sub-chronic treatment with PCP. Rats were administered either PCP (5 mg/kg, i.p.) or vehicle twice a day for 7 days, followed by a 7-day washout period, before testing in NOR. Upon testing, vehicle-treated rats successfully discriminated between novel and familiar objects, an effect abolished in rats that had previously been exposed to PCP treatment. Acute treatment with modafinil (64 mg/kg, p.o.) ameliorated the PCP-induced deficit in novel object exploration, whereas haloperidol (0.1 mg/kg, s.c.), risperidone (0.2 mg/kg, i.p.), and donepezil (3 mg/kg, p.o.) were without significant effect. Given the negligible efficacy of haloperidol and risperidone, and the contradictory data with donepezil to treat CIAS in the clinic, together with the promising preliminary pro-cognitive effects of modafinil in certain subsets of schizophrenic patients, the sub-chronic PCP-NOR abstinence paradigm may represent an attractive option for the identification of potential novel treatments for CIAS.

Phencyclidine-induced cognitive deficits in mice are ameliorated by subsequent subchronic administration of donepezil: role of sigma-1 receptors

This study was undertaken to examine the effects of two acetylcholinesterase inhibitors (donepezil and physostigmine) on cognitive deficits in mice after repeated administration of the NMDA receptor antagonist phencyclidine (PCP). In the novel object recognition test, PCP (10 mg/kg/day for 10 days)-induced cognitive deficits were significantly improved by subsequent subchronic (14 days) administration of donepezil (1.0 mg/kg/day), but not donepezil (0.1 mg/kg/day). Furthermore, the effect of donepezil (1.0 mg/kg/day) on PCP-induced cognitive deficits was significantly antagonized by co-administration of the selective sigma-1 receptor antagonist NE-100 (1.0 mg/kg/day), suggesting the role of sigma-1 receptors in the active mechanisms of donepezil. In contrast, PCP-induced cognitive deficits were not improved by subsequent subchronic (14 days) administration of physostigmine (0.25 mg/kg/day). Moreover, repeated administration of PCP significantly caused the reduction of sigma-1 receptors in the hippocampus. The present study suggests that agonistic activity of donepezil at sigma-1 receptors plays a role in the active mechanisms of donepezil on PCP-induced cognitive deficits in mice. Therefore, it is likely that donepezil would be potential therapeutic drugs for the treatment of the cognitive deficits in schizophrenia.