Donepezil plasma concentrations, CYP2D6 and CYP3A4 phenotypes, and cognitive outcome in Alzheimer's disease

Co-administration of Ceratonia siliqua extract nanoparticles promotes the oral bioavailability and neurotherapeutic efficacy of donepezil in a dementia model

BACKGROUND

This study aimed to assess the herb-drug interactions between crude/silver nanoparticle (SNP)-loaded carob extract (Car, NCar, respectively) and donepezil-HCl (DPZ) and their impact on neurotherapeutic outcomes in a dementia model.

METHODS

Carob pods were subjected to ethanol extraction, and their phytoconstituents were chromatographically analysed. SNP-loaded extract was synthesized and characterized, and dementia-like symptoms were induced in Wistar rats by repeated dosing with 175 mg/kg AlCl3 for 60 days, after which the animals were treated with Car, NCar, DPZ, and combinations of Car/NCar-DPZ for 30 days. The effect of carob formulations on DPZ bioavailability was in-silico profiled and the herb-drug interactions were mathematically assessed as combination indices.

RESULTS

Different formulations significantly improved cognitive/spatial memory functions, restored dysregulated brain redox and cholinergic functions, and markedly inhibited cholinesterase, as reflected by the reduction/absence of amyloid plaques and neurofibrillary tangles. In silico profiling of the major phytoconstituents revealed their non-P-glycoprotein substrate nature and CYP3A4, 2C19, and 2C9 inhibition, which might have improved the oral bioavailability of DPZ. The combination index calculations revealed strong synergy between DPZ and both carob formulations, with the strongest effect exhibited by the DPZ/NCar combination.

CONCLUSION

The co-administration of carob extract/SNPs represents a promising approach for enhancing the neurotherapeutic efficacy of DPZ.

Effect of concomitant use of yokukansan on steady-state blood concentrations of donepezil and risperidone in real-world clinical practice

AIM

Yokukansan is one of the most frequently used herbal medicines that can improve the behavioral and psychological symptoms of dementia. In this exploratory study, we investigated whether yokukansan affects the steady-state blood concentrations of donepezil, risperidone, and the major metabolites of both drugs in a real-world clinical setting.

METHODS

A non-randomized, open-label, single-arm study examining drug-drug interactions was conducted. Fifteen dementia patients taking donepezil for at least 4 weeks and eight schizophrenia patients taking risperidone for at least 2 weeks were orally administered 2.5 g of yokukansan three times a day before or between meals, and blood samples were collected before and 8 weeks after starting co-treatment with yokukansan. Plasma concentrations of donepezil, risperidone, and each metabolite were measured using high-performance liquid chromatography-tandem mass spectrometry and compared before and after the 8-week administration of yokukansan.

RESULTS

The plasma concentrations of donepezil and its metabolites (6-O-desmethyl-donepezil, 5-O-desmethyl-donepezil, and donepezil-N-oxide), risperidone, and its metabolite paliperidone did not differ before and after the 8-week treatment with yokukansan.

CONCLUSIONS

The findings of this study show that the concomitant use of yokukansan may have little clinical impact on the steady-state blood levels of donepezil and risperidone in patients with dementia or schizophrenia.

Machine learning-based virtual screening and molecular modelling studies for identification of butyrylcholinesterase inhibitors as anti-Alzheimer's agent

Butyrylcholinesterase (BChE) is a hydrolase involved in the metabolism and detoxification of specific esters in the blood. It is also implicated in the progression of Alzheimer's disease, a type of dementia. As the disease progresses, the level of BChE tends to increase, opting for a major role as an acetylcholine-degrading enzyme and surpassing the role of acetylcholinesterase. Hence, the development of BChE inhibitors could be beneficial for the latter stages of the disease. In the present study, machine learning (ML) models were developed and employed to identify new BChE inhibitors. Further, the identified molecules were subjected to molecular property filters. The filtered ligands were studied through molecular modelling techniques, viz. molecular docking and molecular dynamics (MD). Support vector machine-based ML models resulted in the identification of 3291 compounds that would have predicted IC50 values less than 200 nM. The docking study showed that compounds ART13069594, ART17350769 and LEG19710163 have mean binding energies of -9.62, -9.26 and -8.93 kcal/mol, respectively. The MD study displayed that all the selected ligands showed stable complexes with BChE. The trajectories of all the ligands were stable similar to the standard BChE inhibitors.Communicated by Ramaswamy H. Sarma.

Pharmacokinetic/Pharmacodynamic Models of an Alzheimer's Drug, Donepezil, in Rats

To investigate the relationship between the pharmacokinetics (PK) and pharmacodynamics (PD) of donepezil (Don), simultaneous examination of the PK of Don and the change in acetylcholine (ACh) in the cerebral hippocampus was analyzed using microdialysis in rats. Don plasma concentrations reached their maximum at the end of a 30-minute infusion. The maximum plasma concentrations (C_maxs) of the major active metabolite, 6-O-desmethyl donepezil, were 9.38 and 13.3 ng/ml at 60 minutes after starting infusions at 1.25 and 2.5 mg/kg doses, respectively. The amount of ACh in the brain increased shortly after the start of the infusion and reached the maximum value at about 30 to 45 minutes, then decreased to the baseline with a slight delay from the transition of the Don concentration in plasma at a 2.5 mg/kg dose. However, the 1.25 mg/kg group showed little increase in ACh in the brain. The PK/PD models of Don, which were constructed using a general 2-compartment PK model with/without Michaelis-Menten metabolism and the suppressive effect of conversion of ACh to choline using an ordinary indirect response model, were able to effectively simulate Don's plasma and ACh profiles. The ACh profile in the cerebral hippocampus at a 1.25 mg/kg dose was effectively simulated using both constructed PK/PD models and parameters obtained at a 2.5 mg/kg dose by the PK/PD models and indicated that Don largely had no effect on ACh. When these models were used to simulate at 5 mg/kg, the Don PK were nearly linear, whereas the ACh transition had a different profile to lower doses. SIGNIFICANCE STATEMENT: Efficacy/safety of a drug and its pharmacokinetics (PK) are closely correlated. Therefore, it is important to understand the relationship between the drug's PK and its pharmacodynamics (PD). A quantitative procedure of achieving these goals is the PK/PD analysis. We constructed the PK/PD models of donepezil in rats. These models can predict the acetylcholine-time profiles from the PK. The modeling technique is a potential therapeutic application to predict the effect when changes in the PK are caused by pathological condition and co-administered drugs.

Neurotherapeutic Effects of Quercetin and Its Metabolite Compounds on Cognitive Impairment and Parkinson's Disease: An In Silico Study

BACKGROUND AND OBJECTIVE

Little is known about the metabolomic profile of quercetin and its biological effects. This study aimed to determine the biological activities of quercetin and its metabolite products, as well as the molecular mechanisms of quercetin in cognitive impairment (CI) and Parkinson's disease (PD).

METHODS

Key methods used were MetaTox, PASS Online, ADMETlab 2.0, SwissADME, CTD MicroRNA MIENTURNE, AutoDock, and Cytoscape.

RESULTS

A total of 28 quercetin metabolite compounds were identified by phase I reactions (hydroxylation and hydrogenation reactions) and phase II reactions (methylation, O-glucuronidation, and O-sulfation reactions). Quercetin and its metabolites were found to inhibit cytochrome P450 (CYP) 1A, CYP1A1, and CYP1A2. The studied compounds demonstrated significant gastrointestinal absorption and satisfied Lipinsky's criterion. Due to their high blood-brain barrier permeability, P-glycoprotein inhibition, anticancer, anti-inflammatory, and antioxidant capabilities, quercetin and its metabolite products have been proposed as promising molecular targets for the therapy of CI and PD. By regulating the expression of crucial signaling pathways [mitogen-activated protein kinase (MAPK) signaling pathway, and neuroinflammation and glutamatergic signaling], genes [brain derived neurotrophic factor (BDNF), human insulin gene (INS), and dopamine receptor D2 (DRD2), miRNAs (hsa-miR-16-5p, hsa-miR-26b-5p, hsa-miR-30a-5p, hsa-miR-125b-5p, hsa-miR-203a-3p, and hsa-miR-335-5p], and transcription factors [specificity protein 1 (SP1), v-rel avian reticuloendotheliosis viral oncogene homolog A (RELA), and nuclear factor Kappa B subunit 1 (NFKB1)], quercetin exhibited its neurotherapeutic effects in CI and PD. In addition to inhibiting β-N-acetylhexosaminidase, quercetin also showed robust interactions and binding affinities with heme oxygenase 1 (HMOX1), superoxide dismutase 2 (SOD2), tumor necrosis factor (TNF), nitric oxide synthase 2 (NOS2), brain-derived neurotrophic factor (BDNF), INS, DRD2, and γ-aminobutyric acid type A (GABAa).

CONCLUSION

This study identified 28 quercetin metabolite products. The metabolites have similar characteristics to quercetin such as physicochemical properties, absorption, distribution, metabolism, and excretion (ADME), and biological activities. More research, especially clinical trials, is needed to find out how quercetin and its metabolites protect against CI and PD.

The Influence of Selected Antipsychotic Drugs on Biochemical Aspects of Alzheimer's Disease

The aim of this study was to assess the potency of selected antipsychotic drugs (haloperidol (HAL), bromperidol (BRMP), benperidol (BNP), penfluridol (PNF), pimozide (PIM), quetiapine (QUET) and promazine (PROM)) on the main pathological hallmarks of Alzheimer's disease (AD). Binary mixtures of donepezil and antipsychotics produce an anti-BuChE effect, which was greater than either compound alone. The combination of rivastigmine and antipsychotic drugs (apart from PNF) enhanced AChE inhibition. The tested antipsychotics (excluding HAL and PNF) significantly reduce the early stage of Aβ aggregation. BRMP, PIM, QUET and PROM were found to substantially inhibit Aβ aggregation after a longer incubation time. A test of human erythrocytes hemolysis showed that short-term incubation of red blood cells (RBCs) with QUET resulted in decreased hemolysis. The antioxidative properties of antipsychotics were also proved in human umbilical vein endothelial cells (HUVEC); all tested drugs were found to significantly increase cell viability. In the case of astrocytes, BNP, PNF, PIM and PROM showed antioxidant potential.

Neurobiological Highlights of Cognitive Impairment in Psychiatric Disorders

This review is focused on several psychiatric disorders in which cognitive impairment is a major component of the disease, influencing life quality. There are plenty of data proving that cognitive impairment accompanies and even underlies some psychiatric disorders. In addition, sources provide information on the biological background of cognitive problems associated with mental illness. This scientific review aims to summarize the current knowledge about neurobiological mechanisms of cognitive impairment in people with schizophrenia, depression, mild cognitive impairment and dementia (including Alzheimer's disease).The review provides data about the prevalence of cognitive impairment in people with mental illness and associated biological markers.

Impact of Plasma Donepezil Concentration on Behavioral and Psychological Symptoms of Dementia in Patients with Alzheimer’s Disease

Background/Aims

The behavioral and psychological symptoms of dementia (BPSD) detract from the quality of life of not only dementia patients but also their family members and caregivers. Donepezil is used to treat Alzheimer's disease and is metabolized via cytochrome P450 (CYP) 2D6 and CYP3A4/5. It is controversial whether donepezil improves or exacerbates BPSD. This study investigated the relationships among BPSD, the pharmacokinetics of donepezil including its metabolite, 6-O-desmethyl donepezil, genetic polymorphisms of CYPs and P-glycoprotein, and patient backgrounds in 52 patients with Alzheimer's disease.

Methods

BPSD were assessed using the Neuropsychiatric Inventory (NPI), with scores ≥20 points defined as severe BPSD. Plasma donepezil and 6-O-desmethyl donepezil concentrations were measured using liquid chromatography–tandem mass spectrometry.

Results

Although significant relationships between NPI scores and plasma donepezil concentrations were not seen, none of the 15 patients (29%) with high plasma donepezil concentrations (≥60 ng/mL) developed severe BPSD. Polymorphisms of CYP2D6, CYP3A5, and ABCB1 did not influence NPI scores. There were no significant relationships between NPI and patient background factors such as dosing regimen, concomitant use of other drugs, or laboratory test results. Two patients who underwent multiple blood samplings over 2 years showed an inverse correlation between plasma donepezil concentrations and NPI scores.

Discussion/Conclusions

These results indicate that higher plasma concentrations of donepezil contribute to preventing or alleviating rather than developing or deteriorating BPSD.

Long-acting injectable donepezil microspheres: Formulation development and evaluation

Novel formulations of donepezil (DNP)-loaded microspheres based on a bio-degradable polymer of poly(lactic-co-glycolic acid) (PLGA) with a one-month duration of effect were developed, aimed at reducing dosing frequency and adverse effects and improving patient adherence. The spherical and monodispersed DNP-loaded microspheres were precisely fabricated by the Inventage Lab Precision Particle Fabrication method (IVL-PPFM®) based on micro-electromechanical systems (MEMS) and microfluidic technology. The types of polymers and end-groups, the drug/polymer ratio (DPR), and the routes of administration for DNP were studied to ensure an effective concentration and desired duration. Laser-light particle size analysis and scanning electron microscopy were used to characterization. Also, non-clinical animal models of beagle dogs are used to optimize DNP formulations and evaluate their pharmacokinetic properties. The PK results showed that the DPR was a critical factor in determining the exposure level and duration of DNR release. Furthermore, the lactide ratio, which varied depending upon the type of polymer, determined the hydrophobic interaction and was also an important factor affecting the desired DNP release. Since DNP shows a large inter-species variation between dogs and humans, PK modeling and simulation of the reference drug (i.e., Aricept®) and DNP-loaded microspheres were used for formulation development to overcome and interpret these variations. In addition, the developed PK model was extrapolated to humans using the estimated PK parameter and published clinical pharmacology data for DNP. The predicted PK profile of the DNP-loaded microsphere in humans showed that the formulation with PLGA 7525A and the DPR of 1/9 could maintain drug concentration for a month and could control initial burst release. The data obtained from the study could be used as scientific evidence for decision-making in future formulation development.

Adverse Drug Reactions of Acetylcholinesterase Inhibitors in Older People Living with Dementia: A Comprehensive Literature Review

The rising of global geriatric population has contributed to increased prevalence of dementia. Dementia is a neurodegenerative disease, which is characterized by progressive deterioration of cognitive functions, such as judgment, language, memory, attention and visuospatial ability. Dementia not only has profoundly devastating physical and psychological health outcomes, but it also poses a considerable healthcare expenditure and burdens. Acetylcholinesterase inhibitors (AChEIs), or so-called anti-dementia medications, have been developed to delay the progression of neurocognitive disorders and to decrease healthcare needs. AChEIs have been widely prescribed in clinical practice for the treatment of Alzheimer's disease, which account for 70% of dementia. The rising use of AChEIs results in increased adverse drug reactions (ADRs) such as cardiovascular and gastrointestinal adverse effects, resulting from overstimulation of peripheral cholinergic activity and muscarinic receptor activation. Changes in pharmacokinetics (PK), pharmacodynamics (PD) and pharmacogenetics (PGx), and occurrence of drug interactions are said to be major risk factors of ADRs of AChEIs in this population. To date, comprehensive reviews in ADRs of AChEIs have so far been scarcely studied. Therefore, we aimed to recapitulate and update the diverse aspects of AChEIs, including the mechanisms of action, characteristics and risk factors of ADRs, and preventive strategies of their ADRs. The collation of this knowledge is essential to facilitate efforts to reduce ADRs of AChEIs.

In Vitro Metabolism of Donepezil in Liver Microsomes Using Non-Targeted Metabolomics

Donepezil is a reversible acetylcholinesterase inhibitor that is currently the most commonly prescribed drug for the treatment of Alzheimer’s disease. In general, donepezil is known as a safe and well-tolerated drug, and it was not associated with liver abnormalities in several clinical trials. However, rare cases of drug-related liver toxicity have been reported since it has become commercially available. Few studies have investigated the metabolic profile of donepezil, and the mechanism of liver damage caused by donepezil has not been elucidated. In this study, the in vitro metabolism of donepezil was investigated using liquid chromatography–tandem mass spectrometry based on a non-targeted metabolomics approach. To identify metabolites, the data were subjected to multivariate data analysis and molecular networking. A total of 21 donepezil metabolites (17 in human liver microsomes, 21 in mice liver microsomes, and 17 in rat liver microsomes) were detected including 14 newly identified metabolites. One potential reactive metabolite was identified in rat liver microsomal incubation samples. Metabolites were formed through four major metabolic pathways: (1) O-demethylation, (2) hydroxylation, (3) N-oxidation, and (4) N-debenzylation. This study indicates that a non-targeted metabolomics approach combined with molecular networking is a reliable tool to identify and detect unknown drug metabolites.

CYP2D6 Predicts Plasma Donepezil Concentrations in a Cohort of Thai Patients with Mild to Moderate Dementia

Purpose

Donepezil, a drug frequently used to treat dementia, is mainly metabolized by cytochrome P450 2D6 (CYP2D6). This study investigated the relationships between CYP2D6 genotype and activity scores as well as predicted phenotype of plasma donepezil concentrations in 86 Thai dementia participants.

Materials and Methods

CYP2D6 was genotyped using bead-chip technology (Luminex xTAG^® v.3). Steady-state trough plasma donepezil concentrations were measured using high-performance liquid chromatography.

Results

Sixteen genotypes were found but the most frequent genotypes detected among our participants were CYP2D6*10/*10 (27.9%) and *1/*10 (26.7%). One-third of the participants had an activity score of 1.25 which predicted that they were normal metabolizers. The overall median (interquartile range) of plasma donepezil concentration was 51.20 (32.59–87.24) ng/mL. Normal metabolizers (NMs) had lower plasma donepezil concentrations compared to intermediate metabolizers (IMs) (41.15 (28.44–67.65) ng/mL vs 61.95 (35.25–97.00) ng/mL). Multivariate analysis showed that CYP2D6 activity score (r² = 0.50) and the predicted phenotype (independent of dose) could predict the plasma donepezil concentration (r² = 0.49).

Conclusion

Plasma donepezil concentration in NMs was lower compared to IMs. Additional studies with larger sample size and use of next-generation sequencing as well as its outcomes are warranted to confirm the benefit of using pharmacogenetic-guided treatment for donepezil.

Impact of CYP2D6, CYP3A5, and ABCB1 Polymorphisms on Plasma Concentrations of Donepezil and Its Metabolite in Patients With Alzheimer Disease

BACKGROUND

Donepezil is one of the most commonly prescribed drugs for the treatment of Alzheimer disease. It is predominantly metabolized through CYP2D6 and to a lesser extent by CYP3A4/5. There are conflicting reports regarding the influence of CYP2D6, CYP3A5, and ABCB1 polymorphisms on the plasma concentration of donepezil. This study investigated the influence of these polymorphisms and sex on the plasma concentrations of donepezil and its active metabolite, 6-O-desmethyl donepezil (6ODD), in 47 patients with Alzheimer disease.

METHODS

Plasma donepezil and 6ODD concentrations were measured using liquid chromatography tandem mass spectrometry. Sex, the concomitant use of psychotropics, and CYP2D6, CYP3A5, and ABCB1 polymorphisms were analyzed as possible influencers.

RESULTS

The mean plasma concentrations of donepezil and 6ODD were well correlated (R2 = 0.418). The mean plasma concentration ratio of donepezil to 6ODD (metabolic ratio) was significantly lower in intermediate metabolizers of CYP2D6 than in extensive metabolizers. The metabolic ratio in patients receiving psychotropics was significantly lower than in those not receiving psychotropics. Among intermediate metabolizers, patients positive for CYP3A5 *3/*3 showed a significant increase in plasma mean 6ODD concentrations when compared with those who did not express this gene (CYP3A5 *1/*1 or *1/*3).

CONCLUSIONS

Results indicate that the mean plasma concentration ratio of donepezil to 6ODD is associated with CYP2D6 polymorphism and the concomitant use of psychotropics in patients with Alzheimer disease. In intermediate metabolizers, CYP3A5 may play a significant role in the metabolism of donepezil.

Centella asiatica Water Extract Shows Low Potential for Cytochrome P450-Mediated Drug Interactions

Centella asiatica (CA) shows considerable promise for development as a botanical drug for cognitive decline. Its primary bioactive components include triterpene glycosides asiaticoside and madecassoside and their corresponding aglycones asiatic acid and madecassic acid. Exploration of the bioactivity of CA's caffeoylquinic acids is ongoing. In this study, an aqueous extract of CA (CAW-R61J) was evaluated for drug interaction potential through inhibition or induction of P450 enzymes, as required by the US Food and Drug Administration. CAW-R61J was assessed for induction potential of CYP1A2, CYP2B6, and CYP3A4 using transporter-certified cryopreserved human hepatocytes in sandwich culture. Gene expression of these target P450s was quantified, and enzyme activities were determined to confirm gene expression results. No induction was observed up to 16.7 µg/ml CAW-R61J (equivalent to 1.1 µM asiaticoside, 0.8 µM madecassoside, 0.09 µM asiatic acid, and 0.12 µM madecassic acid). Reversible and time-dependent inhibitory effects of CAW-R61J on CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4/5 were evaluated using human liver microsomes. CAW-R61J showed weak reversible inhibition of most of the P450 forms tested, with the strongest being CYP2C9 (IC50 of 330 µg/ml). CAW-R61J (≤1000 µg/ml) was not a time-dependent inhibitor of any of these P450 enzymes. In summary, CAW-R61J had no, or only a weak impact, on P450 induction and inhibition in vitro. The clinical relevance of these results will depend on the in vivo concentration of CAW-R61J components achieved in humans. Plasma triterpene concentrations measured in our recent clinical studies suggest minimal risk of P450-mediated drug interactions by these components. SIGNIFICANCE STATEMENT: A preparation of Centella asiatica is currently under clinical development for the prevention or treatment of cognitive decline. The US Food and Drug Administration required an evaluation of its potential for drug interactions mediated through drug-metabolizing enzymes. This in vitro study revealed minimal induction or inhibition of a range of P450 enzymes, including CYP3A4, by the C. asiatica extract, suggesting a low potential for drug interactions modulated by P450 metabolism.

Are cytochrome P4502D6 and apolipoprotein E genotypes associated with long-term cognitive and functional changes in patients treated with donepezil?

AIM

We investigated the associations of the single-nucleotide polymorphism rs1080985 of cytochrome P4502D6 (CYP2D6) and the apolipoprotein E (APOE) genotypes with cognitive and functional changes in patients treated with donepezil.

METHODS

Sixty-five outpatients with Alzheimer's disease or mixed dementia being treated with donepezil were assessed at baseline and over 27 months. Changes in cognitive status, assessed with the Mini-Mental State Examination, and in functional status, assessed by the Activities of Daily Living Scale and the Instrumental Activities of Daily Living Scale, were evaluated as a function of CYP2D6 and APOE genotypes by using linear mixed models. Multiplicative interactions between the CYP2D6 and APOE genotypes and time were investigated.

RESULTS

Individuals with the mutated CYP2D6 exhibited a slower decline in total Mini-Mental State Examination scores, orientation, registration, and functional status than those with the wild type. A significant interaction between CYP2D6, APOE, and time was found for changes in the Activities of Daily Living Scale; among the ε4 carriers, those with the mutated CYP2D6 exhibited a slower decline on the Activities of Daily Living Scale than those with the wild type.

CONCLUSION

The CYP2D6 and APOE genotypes may modulate the effectiveness of donepezil on cognitive and functional status.

Therapeutic Drug Monitoring of Rivastigmine and Donepezil Under Consideration of CYP2D6 Genotype-Dependent Metabolism of Donepezil

Background

The efficacy of acetylcholinesterase inhibitors (AChE-I) might depend on blood concentration. While rivastigmine metabolism is independent of the cytochrome P450 system, its isoenzymes, especially CYP2D6, metabolize donepezil. CYP2D6 polymorphisms can cause altered enzyme activity resulting in lower or higher than expected drug concentrations of donepezil.

Objective

We investigated correlations between clinical efficacy and serum concentrations of rivastigmine and donepezil under special consideration of CYP2D6 genotype or gene dose–dependent metabolism of donepezil.

Methods

Serum concentrations of donepezil and rivastigmine were measured by liquid chromatography – tandem mass spectrometry (LC-MS/MS). Real-time quantitative polymerase chain reaction (PCR) and allele-specific PCR were performed to assess CYP2D6 genotype and gene dose.

Results

Patients treated with rivastigmine (n=28) or donepezil (n=48) were included in the study. Both gene dose and metabolism type significantly predicted the level of donepezil serum concentration (p=0.019 and p=0.013, respectively). In the rivastigmine group, changes of the word list delayed recall subtest before treatment and under stable medication were significantly associated with rivastigmine serum levels (β=0.465; p=0.018). Drug serum concentrations were outside the recommended range in a substantial percentage of participants, which might have contributed to poor correlations between changes in cognitive measures and drug concentrations. Donepezil serum concentrations significantly depended on CYP2D6 gene dose.

Conclusion

Testing AChE-I serum concentration should be considered in patients without clinical response to treatment or those with severe side effects. Patients with donepezil drug levels outside the recommended range might additionally profit from CYP2D6 genotyping or treatment with an AChE-I independent of CYP metabolism.

Serum Concentrations of Cholinesterase Inhibitors in Patients With Alzheimer's Dementia Are Frequently Below the Recommended Levels

Background

Acetylcholinesterase inhibitors (AChE-I) are recommended for the treatment of cognitive symptoms but also of behavioral and psychological symptoms in dementia. They are widely used not only in Alzheimer's disease, but also in other forms of dementia. Efficacy of treatment might depend on serum concentration of the respective AChE-I.

Objective

In patients with mild to moderate Alzheimer's dementia, we measured serum concentrations of hepatically metabolized donepezil and renally excreted rivastigmine and investigated possible modifiers. Additionally, we looked at correlations between serum concentrations and efficacy for both drugs.

Methods

Serum concentrations of donepezil and rivastigmine were measured by liquid chromatography – tandem mass spectrometry (LC-MS/MS). Real-time quantitative polymerase chain reaction (PCR). Allele specific PCR were performed to determine CYP2D6 genotype and gene dose. Clinical efficacy was assessed by changes of the subtest wordlist delayed recall of the Consortium to Establish a Registry for Alzheimer's Disease-Neuropsychological Assessment Battery (CERAD-NAB).

Results

Sixty-seven patients treated with a stable dosage of donepezil 10 mg (n=41) or rivastigmine 9.5 mg (n=26) were included. Mean serum concentration of donepezil and rivastigmine were 41.2 and 6.5 ng/ml, respectively. Serum concentrations were below the recommended range in 73% of the subjects in the donepezil group and in 65% of the participants in the rivastigmine group. When applying a dose-related reference, ranges 63% of patients in the donepezil group and 32% in the rivastigmine group had concentrations below the expected range. Gene dose, sex, and duration of treatment significantly predicted donepezil serum concentration (p=0.046, p=0.001, p=0.030 respectively). Only for rivastigmine did the serum concentration significantly contribute to the regression model predicting changes on the subtest word list delayed recall (β=0.472; p=0.019).

Conclusions

Serum concentrations of about two thirds of the patients were below the recommended range. When not looking at absolute values but at the dose-related reference ranges, these numbers improved but still 32%, respectively 63% of patients had low serum concentrations. High serum concentrations of rivastigmine predicted clinical response to cognition. Therapeutic drug monitoring might help to identify the cause of poor clinical response to cognition and behavioral and psychological symptoms in patients with AChE-I treatment.

Cognitive symptoms of Alzheimer's disease: clinical management and prevention

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by the accumulation of amyloid β in the form of extracellular plaques and by intracellular neurofibrillary tangles, with eventual neurodegeneration and dementia. There is currently no disease-modifying treatment though several symptomatic medications exist with modest benefit on cognition. Acetylcholinesterase inhibitors have a consistent benefit across all stages of dementia; their benefit in mild cognitive impairment and prodromal AD is unproven. Memantine has a smaller benefit on cognition overall which is limited to the moderate to severe stages, and the combination of a cholinesterase inhibitor and memantine may have additional efficacy. Evidence for the efficacy of vitamin E supplementation and medical foods is weak but might be considered in the context of cost, availability, and safety in individual patients. Apparently promising disease-modifying interventions, mostly addressing the amyloid cascade hypothesis of AD, have recently failed to demonstrate efficacy so novel approaches must be considered.

Influence of CYP2D6, CYP3A5, ABCB1, APOE polymorphisms and nongenetic factors on donepezil treatment in patients with Alzheimer's disease and vascular dementia

PURPOSE

This study aims to evaluate the influence of genetic polymorphisms of CYP2D6, CYP3A5, ABCB1, and APOE genes and nongenetic factors on steady-state plasma concentrations (Cpss) of donepezil and therapeutic outcomes in Thai patients with Alzheimer's disease (AD) and vascular dementia (VAD).

PATIENTS AND METHODS

Eighty-five dementia patients who received donepezil for at least six months were recruited. CYP2D6, CYP3A5, ABCB1, and APOE polymorphisms were genotyped. Cpss of donepezil was measured. Association of genetic and non-genetic factors with Cpss and clinical outcomes of donepezil (cognitive function as measured by the Thai Mental State Examination score; TMSE) were determined by using univariate and multivariate analysis.

RESULTS

Both univariate and multiple linear regression analysis indicated that only CYP2D6*10 allele was associated with higher Cpss (p-value =0.029 and B =0.478, p-value =0.032, respectively) that might influence the clinical outcomes of donepezil. ie, TMSE (p-value =0.010 and B =4.527, p-value =0.001) and ΔTMSE (p-value =0.023 and B =4.107, p-value =0.002), especially in patients with AD. Interestingly, concomitant use of memantine was found to be associated with increased Cpss of donepezil (p-value =0.007 and B =0.511, p-value =0.014). Whereas, co-medication with antidepressant drugs attenuated clinical responses in patients with AD (TMSE: B =-2.719, p-value =0.013 and ΔTMSE: B =-2.348, p-value =0.028). Age was a significant predictor of donepezil response in VAD patients. No significant association of CYP3A5*3, ABCB1 3435C>T or ABCB1 1236C>T, and APOE ε4 genotypes with Cpss or clinical outcomes of donepezil was found in this study.

CONCLUSION

Our results suggests that CYP2D6*10 strongly influences Cpss and there is a trend toward better outcomes of donepezil in patients with AD. Nongenetic factors including concomitant drugs treatment might alter Cpss of donepezil or clinical outcomes.

Atomoxetine improves memory and other components of executive function in young-adult rats and aged rhesus monkeys

Atomoxetine is a norepinephrine reuptake inhibitor and FDA-approved treatment for attention deficit/hyperactivity disorder (ADHD) in children, adolescents, and adults. While there is some evidence that atomoxetine may improve additional domains of cognition beyond attention in both young adults and aged individuals, this subject has not been extensively investigated. Here, we evaluated atomoxetine (in low mg/kg doses) in a variable stimulus duration (vSD) and a variable intertrial interval (vITI) version of the five choice-serial reaction time task (5C-SRTT), and an eight-arm radial arm maze (RAM) procedure in young-adult rats. The compound was further evaluated (in μg/kg-low mg/kg doses) along with nicotine (as a reference compound) and the Alzheimer's disease treatment donepezil in a distractor version of a delayed match to sample task (DMTS-D) in aged monkeys (mean age = 21.8 years). Atomoxetine (depending on the dose) improved accuracy (sustained attention) as well as behaviors related to impulsivity, compulsivity and cognitive inflexibility in both the vSD and vITI tasks and it improved spatial reference memory in the RAM. In the DMTS-D task, both nicotine and atomoxetine, but not donepezil attenuated the effects of the distractor on accuracy at short delays (non-spatial working/short term memory). However, combining sub-effective doses of atomoxetine and donepezil did enhance DMTS-D accuracy indicating the potential of using atomoxetine as an adjunctive treatment with donepezil. Collectively, these animal studies support the further evaluation of atomoxetine as a repurposed drug for younger adults as well older individuals who suffer from deficits in attention, memory and other components of executive function.

[Is it personalized treatment of dementia based on the CYP2D6 gene polymorphism possible?]

Treatment of dementia is an urgent problem of modern neurology. Currently, four drugs are recommended to treat dementia, two of which (donepezil and galantamine) are metabolized with participation of the CYP2D6 enzyme. Genetic heterogeneity of CYP2D6 is associated with different enzyme activity, which affects the concentration of its substrates in blood and, accordingly, the clinical effect and the risk of side-effects of drugs.

AIM

To genotype the single nucleotide polymorphism 1846G>A in the CYP2D6 gene and evaluate its effect on the efficacy and safety of donepezyl in the treatment of Alzheimer's disease (AD).

MATERIAL AND METHODS

Twenty-one patients with AD were genotyped for the CYP2D6 1846G>A polymorphism, which corresponds to the most common in Caucasians allele CYP2D6*4. An effect of this polymorphism on the efficacy and safety of donepezyl was assessed.

RESULTS AND CONCLUSION

There was no association between the CYP2D6 genotype and the efficacy of antidementia therapy (OR=0,44, 95% CI -3.0-1,38; p=0,46).

Pisa syndrome due to donepezil: pharmacokinetic interactions to blame?

We report a case of Pisa syndrome (PS) due to the acetylcholinesterase inhibitor donepezil which may have been precipitated by pharmacokinetic interactions with commonly used medications. PS is defined as a reversible lateral bending of the trunk with a tendency to lean to one side. This is a rare but very distressing complication with this commonly used medication which was not initially recognised, leading to increasing disability for the patient and significant carer stress. Cessation of donepezil and modulation of potential interacting medications resulted in complete resolution.