Simultaneous determination of citalopram and its metabolite in human plasma by LC–MS/MS applied to pharmacokinetic study

Development and validation of UHPLC-MS/MS method for simultaneous quantification of escitalopram and its major metabolites in human plasma and its application in depressed patients

Escitalopram, one of the Selective Serotonin Reuptake Inhibitors (SSRIs), has been widely used in the patients with major depression. In this study, a simple, sensitive and rapid method was established and validated for simultaneous quantification of Escitalopram (S-CT), desmethyl escitalopram (S-DCT), didemethyl escitalopram (S-DDCT) and escitalopram N-Oxide (S-NOCT) in human plasma by ultra-high performance liquid chromatography-tandem with mass spectrometry (UHPLC-MS/MS). Analytes were extracted from plasma by utilizing protein precipitation and then separated on a Hypersil GOLD C18 column (50 mm × 2.1 mm, 1.9 µm). The mobile phase was water: acetonitrile (70:30, v/v) with 0.25% formic acid at a flow-rate of 0.3 mL/min, within a 5 min run time. The mass analysis used positive electro-spray ionization (ESI) in selection reaction monitoring (SRM). The calibration ranges of the analytes were: S-CT: 2.0-200.0 ng/mL, S-DCT: 1.0-100.0 ng/mL, S-DDCT: 0.5-50.0 ng/mL, S-NOCT: 0.2-20.0 ng/mL. The method has been fully validated for selectivity, linearity, accuracy, precision, matrix effect, recovery, stability and carry over and all the results met the admissible limits according to the the US Food and Drug Administration guidelines. Mean plasma concentration (ng/mL) of S-CT, S-DCT, S-DDCT and S-NOCT in 93 depressed patients were 51.10 ± 45.73, 10.32 ± 15.25, 1.53 ± 1.79 and 0.87 ± 0.94, respectively. it is the first time that a UHPLC-MS/MS method for simultaneous quantification of S-CT and its 3 metabolites in human plasma was established and validated.

Validation of a quick and simple chromatographic method for simultaneous quantification of sertraline, escitalopram, risperidone and paliperidone levels in the human plasma

Simultaneous quantification of multiple psychiatric drugs is important for the therapeutic drug monitoring of psychiatric patients. In addition, it would be highly advantageous if the method could be simple, straightforward, and not time-consuming. A 200 µl plasma sample was deproteinized, drugs were separated by a ZORBAX Eclipse XDB-Phenyl column with the mobile phase composed of acetonitrile and 0.1 % formic acid in water (60:40, v/v), and recorded in the MRM mode by using a positive electrospray source with tandem mass spectrometry detection. The dynamic range was 2-256 ng/ml for all the analyzed drugs, except escitalopram (8-256 ng/ml). Quality control samples were prepared in quintuplicates in three relevant concentrations for each drug. Coefficients of determination (R2 ) were higher than 0.99, while the relative difference between nominal and measured concentrations (RE) and CV were lower than 15% for all targets. High performance liquid chromatography coupled with the mass detector (HPLC-MS/MS) method for simultaneous determination of sertraline, escitalopram, risperidone and paliperidone in human plasma was validated with respect to selectivity, linearity, accuracy, precision, matrix effect and stability. This method has significant advantages in terms of low sample volume (200 µl), short preparation time (3 hours) and short runtime per sample (4 minutes).

Determination of Antidepressants in Human Plasma by Modified Cloud-Point Extraction Coupled with Mass Spectrometry

Cloud-point extraction (CPE) is rarely combined with liquid chromatography coupled to mass spectrometry (LC-MS) in drug determination due to the matrix effect (ME). However, we have recently shown that ME is not a limiting factor in CPE. Low extraction efficiency may be improved by salt addition, but none of the salts used in CPE are suitable for LC-MS. It is the first time that the influences of a volatile salt-ammonium acetate (AA)-on the CPE extraction efficiency and ME have been studied. Our modification of CPE included also the use of ethanol instead of acetonitrile to reduce the sample viscosity and make the method more environmentally friendly. We developed and validated CPE-LC-MS for the simultaneous determination of 21 antidepressants in plasma that can be useful for clinical and forensic toxicology. The selected parameters included Triton X-114 concentration (1.5 and 6%, w/v), concentration of AA (0, 10, 20 and 30%, w/v), and pH (3.5, 6.8 and 10.2). The addition of 10% of AA increased recovery twice. For 20 and 30% (w/v) of AA, three phases were formed that prolonged the extraction process. The developed CPE method (6% Triton X-114, 10% AA, pH 10.2) was successfully validated through LC-MS/MS simultaneous determination of 21 antidepressants in human plasma. The linearity was in the range of 10-750 ng/mL (r2 > 0.990).

Toxicity Profile, Pharmacokinetic, and Drug-Drug Interaction Study of Citalopram and Sertraline Following Oral Delivery in Rat: An LC-MS/MS Method for the Simultaneous Determination in Plasma

The burden of depression and other mental disorders is on the rise globally, and successful treatment sometimes requires modifications of drugs and/or dose regimens. The development of novel analytical methods for the determination of antidepressant drugs in biological fluids is thus urgently required. Herein, a sensitive, robust, and rapid liquid chromatographic coupled tandem mass spectrometric method was developed and validated for the determination of citalopram (CIT) and sertraline (SER) in rat plasma after oral administration. The analytes of interest and internal standard (duloxetine (DUL)) were extracted from 100 μL of plasma with solid-phase extraction on an Oasis HLB cartridge followed by the separation with gradient elution with water containing 0.1% formic acid and acetonitrile on an Agilent Eclipse Plus ODS (4.6 × 100 mm, 3.5 μm) column at flow rate 0.2 mL min^-1. The triple quadrupole mass spectrometry was applied via electrospray ionization source for detection. The fragmentation pattern of the protonated CIT, SER, and DUL was elucidated using multiple reaction monitoring of the transitions of m/z 325.2 to 109, 306.1 to 158.9, and 298.1 to 154.1 as [M + H]⁺ for CIT, SER, and DUL, respectively. The proposed method has been validated as per US-FDA bioanalytical guidelines in terms of linearity, accuracy, precision, matrix effects, stability, selectivity, and recovery. The method was linear over the concentration range of 1-2000 and 1-1000 ng mL^-1 with the lower limit of detection of 0.12 and 0.19 ng mL^-1 for CIT and SER, respectively. The interday and intraday precisions and accuracy expressed by the relative standard deviation and the relative standard error were both lower than 11.1% and 2.1%, respectively. The proposed method was successfully applied for the pharmacokinetics and drug monitoring studies of CIT and SER in rat plasma after a single oral dose of 120 mg kg^-1 of CIT and SER. Coadministration of SER with CIT has affected the peak plasma concentrations, maximum plasma concentration time, area under the concentration-time curve, and oral clearance of CIT. Molecular modeling study showed that SER could competitively inhibit CYP2D6, the main enzyme involved in CIT metabolism. A possible drug-drug interaction in psychiatric patients undergoing chronic SER and CIT treatment is therefore worthy of more attention in an effort to avoid side effects and serotonin syndrome.

Micellar liquid chromatographic method for the simultaneous determination of citalopram hydrobromide with its two demethylated metabolites. Utility as a diagnostic tool in forensic toxicology

A micellar liquid chromatographic method has been developed for the simultaneous determination of citalopram hydrobromide (CTA) with its two demethylated metabolites namely; desmethyl citalopram hydrochloride (DCTA) and didesmethyl citalopram tartrate (DDCTA). Separation was conducted on a C18 column using a mobile phase composed of 0.18 M sodium dodecyl sulphate (SDS), 15% 1-propanol, 0.3% tri-ethylamine, adjusted to pH 4 with 0.2 M o-phosphoric acid and adopting UV detection at 240 nm. Analysis was performed at 60 °C applying a flow rate of 2 mL/min. The proposed method was linear over the concentration ranges of 1.0-200.0, 0.6-200.0, and 0.5-200.0 μg/mL for CTA, DCTA, and DDCTA respectively, with corresponding limits of detection (LOD) of 0.5, 0.4, and 0.3 μg/mL and limits of quantification (LOQ) of 0.8, 0.5, and 0.4 μg/mL. The method was fully validated which allowed its application for the determination of CTA in its tablets. Moreover, the proposed method was extended to assay CTA with its metabolites in rat tissue organs samples which allowed the method to be used as a diagnostic tool in forensic toxicology.

Simultaneous Quantification of Citalopram and its Main Metabolite, Desmethylcitalopram, in Human Saliva by UHPLC

Background:

This study was designed to develop a reliable method for simultaneous quantita-tion of Citalopram (CIT) and its main active metabolite, Desmethylcitalopram (DCIT), in saliva of patients undergoing treatment with CIT.

Methods:

To compare two procedures of saliva purification, Solid-Phase (SPE) and Liquid-Liquid (LLE) extractions, saliva samples obtained from healthy volunteers were spiked with adequate quantities of CIT and DCIT. Different cartridges were used for SPE, while dichloromethane for LLE. Chromatographic separation and quantitation were carried out by UHPLC with DAD detector using a C-18 column and a mixture of acetonitrile and redistilled water (37:63, v:v) with the addition of formic acid (pH 3.5) as a mobile phase.

Results:

A comparison of both purification procedures showed that the most satisfactory results were obtained by SPE using Discovery C18 cartridge and redistilled water with formic acid (pH 3.5) as a washing solvent. Dichloromethane proved to be the best extractant in LLE. Both procedures enabled the separation of analytes from human saliva with high precision and recovery.

Conclusions:

Validation of the developed UHPLC procedure revealed that, regardless of how the sample was purified, the method was characterized by good linearity (between 10 and 1000 ng/mL), sensitivity, reproducibility, specificity and low values of limits of detection and quantitation. The limits of quantitation were 4.0 and 8.0 ng/mL for SPE and LLE, respectively. The efficiency of the method in therapeutic drug monitoring of CIT and DCIT in saliva of patients was confirmed.

Inhibition of the Serotonin Transporter Is Altered by Metabolites of Selective Serotonin and Norepinephrine Reuptake Inhibitors and Represents a Caution to Acute or Chronic Treatment Paradigms

Previous studies of transgenic mice carrying a single isoleucine to methionine substitution (I172M) in the serotonin transporter (SERT) demonstrated a loss of sensitivity to multiple antidepressants (ADs) at SERT. However, the ability of AD metabolites to antagonize SERT was not assessed. Here, we evaluated the selectivity and potency of these metabolites for inhibition of SERT in mouse brain-derived synaptosomes and blood platelets from wild-type (I172 mSERT) and the antidepressant-insensitive mouse M172 mSERT. The metabolites norfluoxetine and desmethylsertraline lost the selectivity demonstrated by the parent compounds for inhibition of wild-type mSERT over M172 mSERT, whereas desvenlafaxine and desmethylcitalopram retained selectivity. Furthermore, we show that the metabolite desmethylcitalopram accumulates in the brain and that the metabolites desmethylcitalopram, norfluoxetine, and desvenlafaxine inhibit serotonin uptake in wild-type mSERT at potencies similar to those of their parent compounds, suggesting that metabolites may play a role in effects observed following AD administration in wild-type and M172 mice.

Estimation of CYP2D6*10 genotypes on citalopram disposition in Chinese subjects by population pharmacokinetic assay

WHAT IS KNOWN AND OBJECTIVE

There is great interindividual variability in citalopram (CIT) pharmacokinetics. We attempted to establish a population pharmacokinetic (PPK) model of CIT in Chinese healthy subjects, to evaluate the effect of genetic polymorphism on CIT pharmacokinetics and to compare the PPK and non-compartmental (NCA) assays in the estimation of CIT bioequivalence.

METHODS

Blood samples of 23 healthy subjects were collected after administration of CIT; plasma concentration of CIT was analysed using LC/MS-MS. CYP2C19 and CYP2D6*10 genotypes were determined. PPK model was established by using nonlinear mixed-effect modelling (NONMEM). The model was evaluated using goodness-of-fit plots and relative error measurements. Bioequivalence of CIT was evaluated by both PPK and NCA method.

RESULTS AND DISCUSSION

The estimated population absorption rate constant (ka ), clearance (CL/F) and volume of distribution (Vd/F) in Chinese healthy subjects are 0.64 L/h, 12.7 L/h and 705 L, respectively. Different CYP2C19 and CYP2D6 genotypes have impacts on CIT pharmacokinetics. There is about 5.5% decrement of CL/F for each CYP2C19*2 or CYP2D6*10 allele. The 90% confidence interval of CIT bioavailability obtained from NCA and PPK model were 96.4-105.4% and 92.5-103.4%, respectively.

WHAT IS NEW AND CONCLUSION

The PPK of CIT is best characterized by a one-compartment disposition model with first-order absorption. CYP2C19 and CYP2D6 genotypes have impacts on the CL/F of CIT. Bioequivalence of CIT can be estimated by both NCA and PPK model.

Fragmentation of toxicologically relevant drugs in positive-ion liquid chromatography-tandem mass spectrometry

The identification of drugs and related compounds by LC-MS-MS is an important analytical challenge in several application areas, including clinical and forensic toxicology, doping control analysis, and environmental analysis. Although target-compound based analytical strategies are most frequently applied, at some point the information content of the MS-MS spectra becomes relevant. In this article, the positive-ion MS-MS spectra of a wide variety of drugs and related substances are discussed. Starting point was an MS-MS mass spectral library of toxicologically relevant compounds, available on the internet. The positive-ion MS-MS spectra of ∼570 compounds were interpreted by chemical and therapeutic class, thus involving a wide variety of drug compound classes, such benzodiazepines, beta-blockers, angiotensin-converting enzyme inhibitors, phenothiazines, dihydropyridine calcium channel blockers, diuretics, local anesthetics, vasodilators, as well as various subclasses of anti-diabetic, antidepressant, analgesic, and antihistaminic drugs. In addition, the scientific literature was searched for available MS-MS data of these compound classes and the interpretation thereof. The results of this elaborate study are presented in this article. For each individual compound class, the emphasis is on class-specific fragmentation, as discussing fragmentation of all individual compounds would take far too much space. The recognition of class-specific fragmentation may be quite informative in determining the compound class of a specific unknown, which may further help in the identification. In addition, knowledge on (class-specific) fragmentation may further help in the optimization of the selectivity in targeted analytical approaches of compounds of one particular class.