Liquid chromatography tandem mass spectrometry assay for the simultaneous determination of venlafaxine and O-desmethylvenlafaxine in human plasma and its application to a bioequivalence study

All-Solid State Potentiometric Sensors for Desvenlafaxine Detection Using Biomimetic Imprinted Polymers as Recognition Receptors

Using single-walled carbon nanotubes (SWCNTs) as an ion-to-electron transducer, a novel disposable all-solid-state desvenlafaxine-selective electrode based on a screen-printed carbon paste electrode was created. SWCNTs were put onto the carbon-paste electrode area, which was protected by a poly (vinyl chloride) (PVC) membrane with a desvenlafaxine-imprinted polymer serving as a recognition receptor. Electrochemical impedance spectroscopy and chronopotentiometric techniques were used to examine the electrochemical characteristics of the SWCNTs/PVC coating on the carbon screen-printed electrode. The electrode displayed a 57.2 ± 0.8 mV/decade near-Nernstian slope with a 2.0 × 10^-6 M detection limit. In 10 mM phosphate buffer, pH 6, the ODV-selective electrodes displayed a quick reaction (5 s) and outstanding stability, repeatability, and reproducibility. The usefulness of electrodes was demonstrated in samples of ODV-containing pharmaceutical products and human urine. These electrodes have the potential to be mass produced and employed as disposable sensors for on-site testing, since they are quick, practical, and inexpensive.

A Systematic Review on Analytical Methods to Determine Chiral and Achiral Forms of Venlafaxine and its Metabolite O-desmethylvenlafaxine

Background:

Venlafaxine (VEN) is a bicyclic phenylethylamine derivative and possesses a marked structural difference from other antidepressant drugs present in the market. It works by eliciting the neurotransmitter action in CNS. It occurs in two enantiomeric forms i.e. R and S VEN. After the first pass metabolism, it gets metabolized into more active form O-desmethylvenlafaxine (ODV) which also exist in the enantiomeric forms. So it is important to develop a suitable analytical and bioanalytical method for the determination of VEN and its metabolite to quantify them accurately.

Methods and Results:

The current review summarizes methods to determine chiral and achiral forms of VEN and ODV. According to the literature, it is clear that most widely used method for the determination of VEN and ODV is liquid chromatography-mass spectroscopy, other methods used for routine analysis include UV spectroscopy, reverse phase high-performance liquid chromatography with PDA detector. For the determination of enantiomeric forms of VEN and ODV, different chiral columns have been utilized. Capillary electrophoresis with charged cyclodextrins is also used to determine the enantiomeric forms.

Conclusion:

Various analytical methods for determining VEN and its metabolite in different matrices have been discussed thoroughly in the present review.

Magnetic solid-phase extraction coupled with UHPLC-MS/MS for four antidepressants and one metabolite in clinical plasma and urine samples

Aim: Routine therapeutic drug monitoring is highly recommended since common antidepressant combinations increase the risk of drug-drug interactions or overlapping toxicity. Materials & methods: A magnetic solid-phase extraction by using C₁₈-functionalized magnetic silica nanoparticles (C₁₈-Fe₃O₄@SiO₂ NPs) as sorbent was proposed for rapid extraction of venlafaxine, paroxetine, fluoxetine, norfluoxetine and sertraline from clinical plasma and urine samples followed by ultra-HPLC-MS/MS assay. Results: The synthesized C₁₈-Fe₃O₄@SiO₂ NPs showed high magnetization and efficient extraction for the analytes. After cleanup by magnetic solid-phase extraction, no matrix effects were found in plasma and urine matrices. The analytes showed LODs among 0.15-0.75 ng ml^-1, appropriate linearity (R ≥ 0.9990) from 2.5 to 1000 ng ml^-1, acceptable accuracies 89.1-110.9% with precisions ≤11.0%. The protocol was successfully applied for the analysis of patients' plasma and urine samples. Conclusion: It shows high potential in routine therapeutic drug monitoring of clinical biological samples.

Determination of Venlafaxine in Bulk and Pharmaceutical Formulations Using Stability Indicating RP-HPLC Method with UV Detector

Background:

A robust and validated analytical method is a key component at various stages of pharmaceutical product development to ensure identity, purity and quality of drugs and formulations.

Objective:

The aim of proposed work was to develop and validate a simple, sensitive and stability indicating high performance liquid chromatographic method for the estimation of venlafaxine hydrochloride in bulk and formulations for routine analysis as well as for preformulation studies.

Methods:

Efficient chromatographic separation has been performed on a HpyercloneTM 5µm BDS C18 column using a mobile phase consisting of a mixture of phosphate buffer (25 mM, pH 3.0) and acetonitrile (70:30 v/v) at a flow rate of 1 ml min-1. Venlafaxine hydrochloride was analyzed using UV detector at 225nm. Developed method was validated as per ICH guidelines.

Results:

The method has demonstrated linearity over the range of 100 to 2000 ng ml-1 with regression equation, mean peak area (y) = 93.32 x concentration - 322.00 (R2 = 1). The method has demonstrated good and consistent recovery (99.34 to 101.16%). Precision of the method reflected by the relative standard deviation values at intra-day and inter-day levels was less than 1.79%. The detection and quantitation limits were 6.55 ng ml-1 and 19.84 ng ml-1 respectively indicating sensitivity of the method. The method was successfully applied for the estimation of venlafaxine hydrochloride in marketed and inhouse formulations. Also, developed method was successfully used in drug-excipients compatibility studies for VEN.

Conclusion:

The method was found to be accurate, precise, sensitive and selective for the determination venlafaxine hydrochloride in bulk and pharmaceutical formulations.

Optimized bio-analytical methods development and comparative pharmacokinetic studies of four antidepressants in Egyptian population based on gender difference

The pharmacokinetics (PK) and pharmacodynamics of many oral antidepressants (OADs) vary substantially among different genders and ethnicities. Likewise is their therapeutic effectiveness, time to response and the incidence of adverse drug events. The aim of this study is to compare the PK of four OADs (desvenlafaxine; DSV, venlafaxine; VLX, escitalopram; ESP, and agomelatine; AGT) among Egyptian males and females. In this study, LC-MS/MS methods were developed and validated for determining the four OADs in human plasma. Samples were prepared by liquid-liquid extraction. Chromatographic separation was performed on reversed-phase C₁₈ columns followed by positive-ion electrospray ionization and MS/MS detection. The assays were applied for the assessment of PK parameters in human volunteers (n = 95). The developed methods were linear, accurate, and precise for the determination of DSV, VLX, ESP and AGT with extraction recovery of 90 ± 2.0, 98 ± 1.0, 90 ± 1.3 and 87 ± 4.3%, respectively. OADs levels were successfully measured in subjects' plasma and PK parameters were calculated. A prevalent inter-individual variation in PK of the studied OAD was observed. The PK profile of DSV, VLX or ESP did not vary significantly between male and female subjects (p = 0.07-0.98; confidence level (CL) = 95) while the PK of AGT exhibited a significant gender-based variation in both the C_max and the AUC_∞ (p = 0.047 and 0.0015; CL = 95). Our results highlight the significance of therapeutic drug monitoring of OADs. Further, it indicates the dose adjustment based on gender difference may not be relevant for DSV, VLX and ESP while it may be considered for AGT.

First MEPS/HPLC assay for the simultaneous determination of venlafaxine and O-desmethylvenlafaxine in human plasma

Background: A new high-performance liquid chromatography–fluorescence detection assay based on microextraction by packed sorbent as sample preparation approach is described to quantify venlafaxine (VEN) and its main metabolite [O-desmethylvenlafaxine (ODV)]in human plasma. Methods & results: Chromatographic separation of the target analytes (VEN and ODV) and internal standard (licarbazepine) was achieved in less than 6 min on a reverse-phase C18 column using isocratic elution. Calibration curves were linear in the ranges of 10–1000 ng ml-1 for VEN and 20–1000 ng ml-1 for ODV. The method was successfully applied to real plasma samples. Conclusion: This microextraction by packed sorbent/high-performance liquid chromatography–fluorescence detection assay offers a cost-effective tool that can be applied for therapeutic drug monitoring and also support other pharmacokinetic-based studies in humans.

A fully validated method for the simultaneous determination of 11 antidepressant drugs in whole blood by gas chromatography-mass spectrometry

Antidepressant drugs are widely used for the treatment of depression and other psychiatric disorders and as a result they are involved in numerous clinical and forensic cases. The aim of this study was the development, optimization and validation of a simple, specific and sensitive GC/MS method for the simultaneous determination of 11 antidepressant drugs and 4 of their metabolites (amitriptyline, citalopram, clomipramine, fluoxetine, fluvoxamine, maprotiline, desmethyl-maprotiline, mirtazapine, desmethyl-mirtazapine, nortriptyline, paroxetine, sertraline, desmethyl-sertraline, venlafaxine and desmethyl-venlafaxine) in whole blood. The combination of solid-phase extraction with derivatization using heptafluorobutyric anhydride efficiently reduced matrix effect and improved sensitivity of the method. In this assay, protriptyline was used as internal standard. Absolute recovery values for all analytes were ranged from 79.2 to 102.6%. LODs and LOQs were found to be between 0.30-1.50 μg/L and 1.00-5.00 μg/L, respectively. The calibration curves were linear (R(2)≥0.990) within the range of 5.00-1000 μg/L for all analytes. Accuracy expressed as the % E(r) was found to be between -12.3 and 12.2%. Precision expressed as the % RSD was found to be less than 11.7% for all antidepressants. The developed method proved to be suitable for routine work and it was used to successfully analyze more than 2500 clinical and forensic blood samples.

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.

Bioequivalence of venlafaxine modified-release capsule revisited with an innovative approach using experimental and predictive models

Background: To evaluate the venlafaxine:O-desmethyl venlafaxine (active metabolite) in vivo formation ratio (MR) in three independent bioequivalence (BE) studies consisting of single-dosed (under fasted and fed conditions) and multiple-dosed clinical trials on healthy subjects. The pooled data pharmacokinetic (PK) analysis demonstrates a model to conduct enantiomer/racemate/active metabolite bioanalysis for regulatory submission of bioavailability/bioequivalence (BA/BE) studies using an interesting MR concept. Results: BE was established for all three studies. Moreover, the venlafaxine:O-desmethyl venlafaxine MR for Cmax and AUClast differed by more than 50% for fasted and fed single-dosed studies, while pooled data analysis found the MR for Cmax to be approximately 0.63 and the AUC to be approximately 0.36 for both test and reference drugs. However, negligible variation was observed for both rate and extent of drug and active metabolite absorption into the systemic circulation at steady state, as the MR for both Cmax and AUC was approximately 0.62. Conclusions: The applications/consequences of the above results are immense. First, an achiral assay for venlafaxine and O-desmethyl venlafaxine estimation in human plasma has been justified for the regulatory acceptance of BA/BE studies, supported with both single- and multiple-dosed PK data showing negligible variation in terms of MR at Cmax. Second, the current investigation shows the MR to be within ±10% when compared with the single-dosed reported study on a western population. Third, the racial effect would not lead to any significant clinical outcome using an interchangeable venlafaxine 150-mg capsule manufactured by Ranbaxy with an Efexor 150-mg capsule manufactured by Wyeth. Furthermore, a decision tree is proposed to evaluate if a racemate or an enantiomer drug and active metabolite bioanalysis should be executed for BA/BE regulatory submission using respective achiral or chiral assays when the drug moiety is a racemate or an enantiomer, formulated in modified-release dosage forms.