Optimized method development and validation for determining donepezil in rat plasma: A liquid-liquid extraction, LC-MS/MS, and design of experiments approach.

Donepezil (DPZ), a piperidine-based reversible cholinesterase inhibitor, finds extensive use in treating Alzheimer's disease (AD). Originally designed as an oral formulation, DPZ encounters drawbacks such as a brief duration of action and reduced treatment effectiveness in elderly patients with memory impairment or difficulty swallowing medications. To address these issues and improve patient compliance, researchers are actively exploring alternative DPZ formulations. Consequently, reliable methods are necessary to quantitate DPZ in biological samples for in vivo assessment. Therefore, we propose an efficient, sensitive, wide-dynamic, and cost-effective method for quantitating DPZ in rat plasma. Our method employs liquid-liquid extraction (LLE) followed by liquid chromatography and tandem mass spectrometry, enabling in vivo evaluation of novel DPZ formulations. Notably, our method requires only 20 µL of rat plasma and employs icopezil as the internal standard-a cost-effective compound with chemical similarity to DPZ. We meticulously optimized LLE conditions, taking into account factor interactions through design of experiments (DOE). Our rapid and straightforward extraction and purification involved using 500 µL of pure methyl tert-butyl ether to extract DPZ from the sample within five minutes. The dynamic range of the method extends from 0.5 ng/mL to 1,000 ng/mL, demonstrating excellent sensitivity and suitability for pharmacokinetic studies across diverse DPZ formulations. Following the FDA guidelines, we rigorously validated the developed method, evaluating selectivity, linearity (with a coefficient of determination ≥0.9999), accuracy (ranging from 96.0% to 109.6%), precision (≤13.9%), matrix effect (92.2% to 103.8%), recovery (98.5% to 106.8%), the lower limit of quantitation (0.5 ng/mL), and stability. Finally, we effectively employed the validated method for the long-term pharmacokinetic assessment of a DPZ formulation. We expect that this approach will make a substantial contribution to the advancement of new DPZ formulations, ultimately benefiting individuals afflicted by AD.

Simultaneous estimation of rutin and donepezil through RP-HPLC: implication in pharmaceutical and biological samples.

Aim: A HPLC method was developed and validated for the novel combination of rutin (RN) and donepezil (DNP). Materials & methods: RN and DNP were simultaneously eluted through a C18 column (Ø 150 × 4.6 mm) with a 60:40 v/v ratio of 0.1% formic acid aqueous solution to methanol at 0.5 ml/min. Results: The purposed method was found linear, selective, reproducible, accurate and precise with percent RSD less than 2. The limit of quantification for RN and DNP was found 3.66 and 3.25 µg/ml, respectively. Conclusion: Validated as per the ICH guidelines, the developed method efficiently quantified RN and DNP co-loaded in DQAsomes (121 nm) estimating matrix effect, release profile, entrapment efficiency, loading efficiency and in vivo plasma kinetics.

[Box: see text].

A green micelle-enhanced first derivative synchronous fluorescence approach for determination of donepezil HCl and trazodone HCl in their pure state, pharmaceutical dosage form and spiked human plasma.

The study's objective is to establish an eco-friendly, sensitive and economical quantitative methodology for the concurrent analysis of donepezil HCl (DPZ) and trazodone HCl (TRZ) in raw materials, tablets and human plasma. The first derivative synchronous fluorescence spectroscopic (FDSFS) technique was applied at constant wavelength difference (∆λ = 120) for assessment of DPZ and TRZ at each other's zero-crossing point at 279 nm and 297 nm, respectively. The submitted technique was validated in accordance with ICH Q2 R1 guidelines and the linearity of the standard calibration curve was observed over the concentration range of 10-500 ng/ml for DPZ and 20-1,000 ng/ml for TRZ. The detection limits (LOD) were found to be 2.65 and 5.4 ng/ml, and the limits of quantitation (LOQ) were 8.05 and 16.3 ng/ml for DPZ and TRZ, respectively. This technique was used further to quantify the studied medications in their laboratory-prepared mixtures, commercial tablets and spiked plasma samples. The results obtained were not significantly different from those acquired from the comparison methods, indicating the high accuracy and precision of the proposed method. Furthermore, the ecological friendliness of the suggested method was evaluated and proven to be excellent using Green Analytical Procedure Index (GAPI) and Analytical GREEnness (AGREE) evaluation tools.

The measured CSF/plasma donepezil concentration ratio but not individually measured CSF and plasma concentrations significantly increase over 24 h after donepezil treatment in patients with Alzheimer's disease.

BACKGROUND: The acetylcholinesterase inhibitor donepezil is administered as a treatment for Alzheimer's disease (AD). However, the appropriate donepezil dosage is still a matter of debate. METHODS: Forty AD patients receiving 10 mg/day of donepezil were randomly divided into four groups based on the time of plasma and cerebrospinal fluid (CSF) sampling: 6 h (n = 5), 12 h (n = 12), 18 h (n = 6) and 24 h (n = 17) after donepezil administration. High-performance liquid chromatography measured the donepezil concentration in plasma samples and CSF samples collected at 4-time points. RESULTS: Plasma and CSF levels among the groups were not significantly different. Conversely, the CSF/plasma donepezil concentration ratio considerably increased in the 24 h group compared to the 6 h (p < 0.005) and 12 h (p < 0.05) groups. CONCLUSION: The measurement of the CSF/plasma donepezil concentration ratio could be used to better evaluate the optimal dose of donepezil.

[Pharmacokinetics/Pharmacodynamic Analysis to Link Pharmacokinetics to Efficacy and Drug Interaction of Alzheimer's Disease Drugs].

In recent years, the number of patients with Alzheimer's type dementia continues to increase year by year. As a first-line drug, cholinesterase inhibitor is used. There is a close relationship between the time course of the drug plasma concentration (pharmacokinetics; PK) and the time course of its effects and side effects (pharmacodynamics; PD). However, the relationship between PK and PD is not simply that plasma concentrations are proportional to the effects. The effect is expressed through the characteristics of various pharmacokinetic processes. Therefore, it is important to investigate the transition of effects accompanying its pharmacokinetics. We conducted a fundamental PK/PD analysis using donepezil. Time course of acetylcholine in the hippocampus was investigated with relation to its PK after donepezil administration using rats. The PK and PD characteristics of the drug, including its active metabolite, were investigated. Additionally, Alzheimer's type dementia drugs are often given in combination with antiplatelet drugs such as cilostazol. It is reported that donepezil and cilostazol interact clinically, partly due to inhibition in the efflux transporters in certain tissues. There are various transporters in the body, and interactions through them may cause unexpected changes in the effects. So, it is important to calculate the correlation between the donepezil level in plasma and tissues after their combined administration. From the PK/PD point of view, the results of this study will provide insight into the time course of effects and the characteristics of drug-drug interaction in clinical practice.

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.

Enhanced anti-amnestic effect of donepezil by Ginkgo biloba extract (EGb 761) via further improvement in pro-cholinergic and antioxidative activities.

ETHNOPHARMACOLOGICAL RELEVANCE: EGb 761 is a standardized dry extract of Ginkgo biloba L. leaves traditionally used by Eastern Asia and has been associated with beneficial effects on neurodegeneration disorders, including Alzheimer's disease. AIM OF THE STUDY: Since beneficial interactions between EGb 761 and donepezil have been observed in previous clinical studies, the current study was proposed aiming to further explore related mechanisms from both pharmacokinetics and pharmacodynamics aspects. MATERIALS AND METHODS: Pharmacodynamic interactions were studied in scopolamine-induced cognitive impairment rats received two-weeks treatment of vehicle, EGb 761 and/or donepezil by the Morris water maze test and ex vivo evaluation of biomarkers of cholinergic transmission and oxidative stress in rat brain. In the meantime, pharmacokinetic profiles of donepezil and bilobalide were obtained and compared among all treatment groups. In addition, impact of the bioavailable EGb 761 components on donepezil brain penetration was evaluated with the hCMEC/D3 cell monolayer model. RESULTS: Scopolamine-induced rats with co-treatment of EGb 761 and donepezil had significantly improved cognitive function in the Morris water maze test with increased brain levels of superoxide dismutase and decreased brain levels of acetylcholinesterase and malondialdehyde than that with treatment of only EGb 761 or donepezil. Despite such beneficial pharmacodynamics outcomes, the two-week co-treatment of EGb 761 and donepezil did not alter the plasma pharmacokinetics and brain uptake of donepezil or bilobalide, which was further verified in the hCMEC/D3 monolayer model. CONCLUSION: Co-administration of EGb 761 and donepezil exerted better anti-amnestic effect via further enhanced pro-cholinergic and antioxidative effects of EGb 761 or donepezil in scopolamine-induced cognitive impairment rat without alteration in their systemic/brain exposure.

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 CYP 2D6 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 (ß=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.

Pharmacokinetic Evaluation by Modeling and Simulation Analysis of a Donepezil Patch Formulation in Healthy Male Volunteers.

INTRODUCTION: This study characterized the pharmacokinetics (PKs) of a donepezil patch formulation currently under development, using mixed effect modeling analysis, and explored optimal patch dosing regimens in comparison with the donepezil oral formulation. METHODS: PK data used in this analysis were from 60 healthy Korean male subjects participating in two Phase I studies, where subjects received single or multiple doses of donepezil of 43.75, 87.5, and 175 mg via patches, and 12 of them received a single oral dose of 10 mg of donepezil, followed by a single dose of donepezil via a patch. Donepezil PKs were analyzed by nonlinear mixed effect modeling using NONMEM software. RESULTS: A well-stirred model with two-compartment distribution and delayed absorption was chosen as the best model for the oral formulation. The PKs of donepezil after the patch applications were best described by a two-compartment linear model with zero-order absorption (D2) and absorption delay. The relative bioavailability (BA) of donepezil after the patch application compared with oral dosing was described to be affected by the duration of patch application. CONCLUSION: PK simulations based on the chosen PK models suggested that, overall, donepezil exposure in plasma is similar whether with 10 mg of oral donepezil every 24 h or a 175 mg patch every 72 h, and likewise with 5 mg of oral donepezil every 24 h or an 87.5 mg patch every 72 h.

Simultaneous determination of donepezil, 6-O-desmethyl donepezil and spinosin in beagle dog plasma using liquid chromatography‒tandem mass spectrometry and its application to a drug-drug interaction study.

Spinosin, which is traditionally used for sedation and sleep disorders, has recently shown potential effects in alleviating memory loss. As spinosin is the main bioactive component in a standardized dried 50% ethanol extract of the seeds of Zizyphus jujuba var. spinosa, a Phase IIb clinical trial is ongoing, in Korea for the combination of the above extract formulated in a tablet (DHP1401 tablet) with donepezil hydrochloride (Aricept® tablet) in patients with mild to moderate Alzheimer's disease. Therefore, to promote safety and efficacy evaluations, a reliable method for the simultaneous detection and analysis of the two drugs is needed. Toward this end, in this study, we established and validated a rapid and sensitive LC-MS/MS method for the simultaneous determination of donepezil, its pharmacologically active metabolite 6-O-desmethyl donepezil, and spinosin in beagle dog plasma (50 µL). After optimization of the system, we used methanol for simple protein precipitation. Chromatographic separation was performed using a Phenomenex Luna C18 column (100 × 2.0 mm, 3 µm) with a mobile phase consisting of 0.1% formic acid in acetonitrile-0.1% formic acid in distilled water (2:8, v/v) at a flow rate of 0.65 mL/min. All analytes were detected and quantified in selected reaction monitoring mode. All calibration curves showed good linearity (r ≥ 0.9965) over the concentration range of 0.02-20, 0.02-10, and 0.5-250 ng/mL for donepezil, for 6-O-desmethyl donepezil, and spinosin, respectively. This validated method was then successfully applied to a pharmacokinetic study in beagle dogs with no evidence for potential drug-drug interactions between DHP1401 and donepezil hydrochloride. This information and optimized assay can be useful for the anticipated co-administration of these two drugs in clinical settings.

Development of HPLC method coupled with fluorescence detection for simultaneous determination of donepezil HCl and trazodone HCl in spiked human plasma and tablets dosage forms.

OBJECTIVES: Elderly people with dementia are commonly suffered from sleep disorders. So, the use of Donepezil hydrochloride as anti-Alzheimer drug and Trazodone hydrochloride as antidepressants with hypnotic action is very important in these cases. This study reports about novel and sensitive RP-HPLC method with fluorescence detection for simultaneous bioanalytical determination of Donepezil hydrochloride (DON) and co-administered, Trazodone hydrochloride (TRA) in their pure forms, spiked human plasma and tablets. MATERIALS AND METHODS: Elution of both drugs was achieved with excellent resolution using a RP-C18 Hypersil Gold column and an isocratic mobile phase consisting of phosphate buffer (50mm, pH 4.6): methanol: acetonitrile (60:35:5) with a flow rate of 1.5mL/min and 20µL as injection volume. A Fluorescence detector at 300nm for excitation and 400nm for emission was used. RESULTS: Retention times were 4.3 and 6.3min for Donepezil hydrochloride and Trazodone hydrochloride, respectively. Linearity ranges of the assay were 25-1000 and 50-5000ng/mL and the limits of detection (LOD) and quantitation (LOQ) were 8.52, 15.47 and 25.81, 46.89ng/mL for Donepezil hydrochloride and Trazodone hydrochloride, respectively. CONCLUSION: The high sensitivity of the proposed method enabled the successful determination of the cited drugs in spiked human plasma with mean percentage of recoveries of 91.58±3.34 and 100.30±5.11 for Donepezil hydrochloride and Trazodone hydrochloride, respectively.

Hyperbranched cellulose polyester of oral thin film and nanofiber for rapid release of donepezil; preparation and in vivo evaluation.

Cellulose blended hyperbranched polyester (CHP) and hyperbranched cellulose polyester (HPC) were synthesized by melt condensation method using 2,2-bis (methylol) propionic acid and p-TSA. Obtained polymers were utilized for the preparation of various donepezil loaded thinfilm (CHPF, HPCF) and nanofibers (CHPN, HPCN) using solvent casting and electrospinning technique respectively. Formulated thinfilms and nanofibers were subjected to thermal analysis and microscopic evaluations. Compared with thinfilm formulations, hyperbranched nanofiber has shown lower particle size about 50-100 nm. This might be helped in releasing 98% of drug in the span of 10 min in in vitro studies for HPCN 4 formulation. Further investigation of in vivo bioavailability studies, peak plasma concentration was observed at 3 to 3.5 h for HPCN formulation. Hyperbranched cellulose formulations (HPCN 4) have significantly higher absorption (AUC 0-∞) (1294.1 ±â€¯5.4 ng/mL) than cellulose blended hyperbranched polymer formulations (876.1 ±â€¯6.1 ng/mL). These studies revealed that the hyperbranched nanofiber formulations possess high mechanical strength and good drug release properties. Current study concludes prepared Hyperbranched cellulose nanofiber will be good alternative for commercially available dosage forms for the treatment of Alzheimer's diseases.

Development of bioanalytical HPLC method for simultaneous determination of the antialzhiemer, donepezil hydrochloride and the antidepressant, citalopram hydrobromide in raw materials, spiked human plasma and tablets dosage form.

OBJECTIVES: A novel, fast and sensitive HPLC method has been developed for the simultaneous bioanalytical determination of Donepezil hydrochloride (DON) and Citalopram hydrobromide (CTP) in raw materials, spiked human plasma and tablets. MATERIALS AND METHODS: Elution of both drugs was achieved with very good resolution using a RP-C18 chromatographic column, samples were analyzed using Hypersil Gold (100mm×4.6mm), 5µm particle size column and an isocratic binary mobile phase consists of phosphate buffer (0.05 M): acetonitrile (65:35). A Diode array detector at wavelength 232nm was used. Chromatographic separation was within a short run time (less than 7minutes) for both drugs. RESULTS: Retention times for DON and CTP were 4.5 and 5.8min, respectively. Linear calibration curves were obtained for DON and CTP over the concentration ranges of 0.1-10 and 0.1-50µg/mL. The mean extraction recoveries from spiked plasma were 93.22 and 92.64 for DON and CTP, respectively. The limits of detection and quantification were 0.017, 0.035µg/mL and 0.052, 0.106µg/mL for DON and CTP, respectively. CONCLUSION: The proposed method was successfully applied to the analysis of the cited drugs in raw materials, spiked human plasma and tablets with excellent accuracy and precision.