Simultaneous determination of dextromethorphan, dextrorphan, and guaifenesin in human plasma using semi-automated liquid/liquid extraction and gradient liquid chromatography tandem mass spectrometry

Development of an enantioselective high-performance liquid chromatography-tandem mass spectrometry method for the quantitative determination of methorphan and its O-demethylated metabolite in human blood and its application to post-mortem samples

In the present work an isocratic enantioselective high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the separation and quantitative determination of dextro - and levo -methorphan and their pharmacologically relevant metabolites, dextrorphan and levorphanol, respectively, in human blood samples. The separation of enantiomers of methorphan and metabolites was performed on the polysaccharide-based chiral column Lux AMP in combination with acetonitrile and 5 mM aqueous ammonium bicarbonate pH 11 in the ratio 50:50 (%, v/v) as mobile phase with the flow rate 1 mL/min. The mass spectrometer was operated in scheduled multiple reaction monitoring (MRM) mode, with four transitions for each dextromethorpan, levomethorphan, dextrorphan and dextromethorphan-d3 and two transitions for each levorphanol, levorphanol-d3 and dextrorphan-d3. Application of this method to human post-mortem blood samples confirmed cases of severe overdosing with dextromethorphan, levomethorphan, and less commonly with both.

Physiologically based pharmacokinetic (PBPK) modeling of the role of CYP2D6 polymorphism for metabolic phenotyping with dextromethorphan

The cytochrome P450 2D6 (CYP2D6) is a key xenobiotic-metabolizing enzyme involved in the clearance of many drugs. Genetic polymorphisms in CYP2D6 contribute to the large inter-individual variability in drug metabolism and could affect metabolic phenotyping of CYP2D6 probe substances such as dextromethorphan (DXM). To study this question, we (i) established an extensive pharmacokinetics dataset for DXM; and (ii) developed and validated a physiologically based pharmacokinetic (PBPK) model of DXM and its metabolites dextrorphan (DXO) and dextrorphan O-glucuronide (DXO-Glu) based on the data. Drug-gene interactions (DGI) were introduced by accounting for changes in CYP2D6 enzyme kinetics depending on activity score (AS), which in combination with AS for individual polymorphisms allowed us to model CYP2D6 gene variants. Variability in CYP3A4 and CYP2D6 activity was modeled based on in vitro data from human liver microsomes. Model predictions are in very good agreement with pharmacokinetics data for CYP2D6 polymorphisms, CYP2D6 activity as described by the AS system, and CYP2D6 metabolic phenotypes (UM, EM, IM, PM). The model was applied to investigate the genotype-phenotype association and the role of CYP2D6 polymorphisms for metabolic phenotyping using the urinary cumulative metabolic ratio (UCMR), DXM/(DXO + DXO-Glu). The effect of parameters on UCMR was studied via sensitivity analysis. Model predictions indicate very good robustness against the intervention protocol (i.e. application form, dosing amount, dissolution rate, and sampling time) and good robustness against physiological variation. The model is capable of estimating the UCMR dispersion within and across populations depending on activity scores. Moreover, the distribution of UCMR and the risk of genotype-phenotype mismatch could be estimated for populations with known CYP2D6 genotype frequencies. The model can be applied for individual prediction of UCMR and metabolic phenotype based on CYP2D6 genotype. Both, model and database are freely available for reuse.

Chiral analysis of dextromethorphan and levomethorphan in human hair by liquid chromatography-tandem mass spectrometry

PURPOSE

Methorphan exists in two enantiomeric forms including dextromethorphan and levomethorphan. Dextromethorphan is an over-the-counter antitussive drug, whereas levomethorphan is strictly controlled as a narcotic drug. Chiral analysis of methorphan could, therefore, assist clinicians and forensic experts in differentiating between illicit and therapeutic use and in tracing the source of the drug.

METHODS

A method for enantiomeric separation and quantification of levomethorphan and dextromethorphan in human hair was developed and validated using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Hair was extracted in hydrochloric acid/methanol (1:20, v/v). The supernatant were separated using a Supelco Astec Chirobiotic™ V2 column (250 × 2.1 mm, i.d., 5 μm particle size) and analyzed on a triple quadrupole linear ion trap mass spectrometer in multiple reaction monitoring mode.

RESULTS

The limits of detection for dextromethorphan and levomethorphan were 2 and 1 pg/mg, respectively; the lower limit of quantification was 2 pg/mg for both drugs. Good linearity (r > 0.995) was observed for both analytes over the linear range. Precision values were below 10% for both analytes; accuracy values ranged from 87.5 to 101%. The extraction recoveries were 78.3-98.4%, and matrix effects were 70.5-88.6%. This method was applied to human hair samples from 120 people suspected of methorphan use to further distinguish the drug chirality. Dextromethorphan was detected in all 120 samples at a concentration range of 2.7-19,100 pg/mg, whereas levomethorphan was not detected in any sample.

CONCLUSIONS

A sensitive quantitative method was established for the enantiomeric separation of dextromethorphan and levomethorphan in hair. This is the first study to achieve chiral analysis of methorphan in human hair.

Eco-friendly UPLC-MS/MS analysis of possible add-on therapy for COVID-19 in human plasma: Insights of greenness assessment

Facing the pandemic COVID-19 is of highest priority for all researchers nowadays. Recent statistics indicate that the majority of the cases are home-treated. Two drugs of interest, Guaifenesin and Bromohexine HCl, are among the add-on therapy for treatment of COVID-19 mild cases, which has raised the need for their simultaneous determination. The analysis of the two drugs of interest was described using ultra-performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) in plasma of healthy human volunteers using tetryzoline HCl as an internal standard (IS) after liquid-liquid extraction. The applied chromatographic conditions were Kinetex C₁₈ (100 Å, 2.6 µm X 50 mm X 4.6 mm) column and a mixture of methanol: water (95: 5, v/v) as a mobile phase at flow rate 1 mL/min. The positive ionization mode was used for detecting the ions, by observing the pairs of transition m/z 199 < 125 for GUF, m/z 377 < 114 for BRM and m/z 201 < 131 for IS. The linearity range was from 50 to 1500 ng/mL for GUF and 0.5-50 µg/mL for BRM. Limit of detection (LOD) was found to be 35.16 and 0.43 ng/ml for GUF and BRM, respectively. The method was validated according to FDA guidance. The proposed method was assessed to be more eco-friendly versus the reported method using the greenness assessment tools: National Environmental Methods Index (NEMI), Assessment of Green Profile (AGP), Green Analytical Procedure Index (GAPI) and Eco-Scale. The proposed method was applied for the application of a pilot pharmacokinetic study.

Use of continuous wavelet transform approach for simultaneous quantitative determination of multicomponent mixture by UV-Vis spectrophotometry

In the present paper, a multicomponent analysis approach based on spectrophotometry method was developed for simultaneous determination of Guaifenesin (GU), Chlorpheniramine (CHL) and Pseudoephedrine (PSE) without any separation steps. The method under study is signal processing method based on Continuous Wavelet Transform (CWT) coupled with zero cross point technique. In this paper, CWT method was tested by synthetic ternary mixtures and was applied to the commercial cough syrup as a real sample and assessed by applying the standard addition technique. For demonstrate the accuracy of the results, other applications of signal processing, such as Derivative Transform (DT), Partial Least Squares (PLS) regression and Principal Components Regression (PCR) were used as comparative methods. Afterwards, the obtained results from analyzing the cough syrup by all methods were compared to the High-Performance Liquid Chromatography (HPLC) as a reference method. One-way analysis of variance test at 95% confidence level showed no significant differences between CWT and other applications.

A New UPLC Approach for the Simultaneous Quantitative Estimation of Four Compounds in a Cough Syrup Formulation

A new ultra-performance liquid chromatographic (UPLC) method was developed for the simultaneous estimation of potassium guaiacolsulfonate (PGS), guaifenesin (GUA), diphenhydramine HCl (DIP) and carbepentane citrate (CAR) in a commercial cough syrup. The chromatographic separation of four compounds PGS, GUA, DIP and CAR was performed on a BEH phenyl column (100 × 2.1 mm, 1.7 µm i.d.) using a mobile phase consisting of acetonitrile and 0.1 M HCl (50 : 50, v/v). In addition, the optimized conditions of the chromatographic analysis were found with the flow rate of 0.38 mL/min, the column temperature of 30°C and the injection volume of 1.2 µL with the photodiode array detection of 220 nm. Calibration curves in the concentration ranges of 10-98 µg/mL for PGS, 5-80 µg/mL for GUA, 5-25 µg/mL for DIP and CAR were computed by the regression of the analyte concentration on the chromatographic peak area. The newly developed UPLC method was validated by analyzing the quaternary mixtures of the related compounds, intraday and interday experiment and standard addition samples. After method validation, the proposed UPLC approach was successfully applied for the analysis of the commercial syrup formulation containing PGS, GUA, DIP and CAR compounds.

Postmortem distribution of guaifenesin concentrations reveals a lack of potential for redistribution

Therapeutic (or non-toxic) postmortem guaifenesin blood and liver concentrations have not been previously described. Peripheral blood guaifenesin concentrations were compared to central blood and liver concentrations in eight medical examiner cases. Specimens were initially screened for alcohol and simple volatiles, drugs of abuse, alkaline, and acid/neutral drugs. Guaifenesin, when detected by the acid/neutral drug screen, was subsequently confirmed and quantified by a high performance liquid chromatography procedure. Data suggest that postmortem guaifenesin peripheral blood concentrations may be considered non-toxic to at least 5.4mg/L with liver concentrations to at least 7.0mg/kg. Overall, guaifenesin concentrations ranged from 1.9 to 40mg/L in peripheral blood, 2.2-150mg/L in central blood, and 2.6-36mg/kg in liver. The median guaifenesin central blood to peripheral blood ratio was 1.1 (N=8). Similarly, liver to peripheral blood ratios showed a median value of 0.9L/kg (N=5). Given that a liver to peripheral blood ratio less than 5L/kg is consistent with little to no propensity for postmortem redistribution, these data suggest that guaifenesin is not prone to substantial postmortem redistribution.

Development and validation of a sensitive UHPLC-MS/MS method for the simultaneous analysis of tramadol, dextromethorphan chlorpheniramine and their major metabolites in human plasma in forensic context: application to pharmacokinetics

The prerequisites for forensic confirmatory analysis by LC/MS/MS with respect to European Union guidelines are chromatographic separation, a minimum number of two MS/MS transitions to obtain the required identification points and predefined thresholds for the variability of the relative intensities of the MS/MS transitions (MRM transitions) in samples and reference standards. In the present study, a fast, sensitive and robust method to quantify tramadol, chlorpheniramine, dextromethorphan and their major metabolites, O-desmethyltramadol, dsmethyl-chlorpheniramine and dextrophan, respectively, in human plasma using ibuprofen as internal standard (IS) is described. The analytes and the IS were extracted from plasma by a liquid-liquid extraction method using ethyl acetate-diethyl-ether (1:1). Extracted samples were analyzed by ultra-high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS). Chromatographic separation was performed by pumping the mobile phase containing acetonitrile, water and formic acid (89.2:11.7:0.1) for 2.0 min at a flow rate of 0.25 μL/min into a Hypersil-Gold C18 column, 20 × 2.0 mm (1.9 µm) from Thermoscientific, New York, USA. The calibration curve was linear for the six analytes. The intraday precision (RSD) and accuracy (RE) of the method were 3-9.8 and -1.7-4.5%, respectively. The analytical procedure herein described was used to assess the pharmacokinetics of the analytes in 24 healthy volunteers after a single oral dose containing 50 mg of tramadol hydrochloride, 3 mg chlorpheniramine maleate and 15 mg of dextromethorphan hydrobromide.

MARS: bringing the automation of small-molecule bioanalytical sample preparations to a new frontier

Background: In recent years, there has been a growing interest in automating small-molecule bioanalytical sample preparations specifically using the Hamilton MicroLab® STAR liquid-handling platform. In the most extensive work reported thus far, multiple small-molecule sample preparation assay types (protein precipitation extraction, SPE and liquid–liquid extraction) have been integrated into a suite that is composed of graphical user interfaces and Hamilton scripts. Using that suite, bioanalytical scientists have been able to automate various sample preparation methods to a great extent. However, there are still areas that could benefit from further automation, specifically, the full integration of analytical standard and QC sample preparation with study sample extraction in one continuous run, real-time 2D barcode scanning on the Hamilton deck and direct Laboratory Information Management System database connectivity. Results: We developed a new small-molecule sample-preparation automation system that improves in all of the aforementioned areas. Conclusion: The improved system presented herein further streamlines the bioanalytical workflow, simplifies batch run design, reduces analyst intervention and eliminates sample-handling error.

Chiral analyses of dextromethorphan/levomethorphan and their metabolites in rat and human samples using LC-MS/MS

In order to develop an analytical method for the discrimination of dextromethorphan (an antitussive medicine) from its enantiomer, levomethorphan (a narcotic) in biological samples, chiral analyses of these drugs and their O-demethyl and/or N-demethyl metabolites in rat plasma, urine, and hair were carried out using LC-MS/MS. After the i.p. administration of dextromethorphan or levomethorphan to pigmented hairy male DA rats (5 mg/kg/day, 10 days), the parent compounds and their three metabolites in plasma, urine and hair were determined using LC-MS/MS. Complete chiral separation was achieved in 12 min on a Chiral CD-Ph column in 0.1% formic acid-acetonitrile by a linear gradient program. Most of the metabolites were detected as being the corresponding O-demethyl and N, O-didemethyl metabolites in the rat plasma and urine after the hydrolysis of O-glucuronides, although obvious differences in the amounts of these metabolites were found between the dextro and levo forms. No racemation was observed through O- and/or N-demethylation. In the rat hair samples collected 4 weeks after the first administration, those differences were more clearly detected and the concentrations of the parent compounds, their O-demethyl, N-demethyl, and N, O-didemethyl metabolites were 63.4, 2.7, 25.1, and 0.7 ng/mg for the dextro forms and 24.5, 24.6, 2.6, and 0.5 ng/mg for the levo forms, respectively. In order to fully investigate the differences of their metabolic properties between dextromethorphan and levomethorphan, DA rat and human liver microsomes were studied. The results suggested that there might be an enantioselective metabolism of levomethorphan, especially with regard to the O-demethylation, not only in DA rat but human liver microsomes as well. The proposed chiral analyses might be applied to human samples and could be useful for discriminating dextromethorphan use from levomethorphan use in the field of forensic toxicology, although further studies should be carried out using authentic human samples.

Simultaneous quantification of dextromethorphan and its metabolites dextrorphan, 3-methoxymorphinan and 3-hydroxymorphinan in human plasma by ultra performance liquid chromatography/tandem triple-quadrupole mass spectrometry

A rapid and sensitive ultra performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) method has been developed and validated for the simultaneous quantitative determination of dextromethorphan (DM) and its metabolites dextrorphan (DX), 3-methoxymorphinan (3MM) and 3-hydroxymorphinan (3HM), in human lithium heparinized plasma. The extraction involved a simple liquid-liquid extraction with 1 ml n-butylchloride from 200μl aliquots of plasma, after the addition of 20 μl 4% (v/v) ammonium hydroxide and 100 μl stable labeled isotopic internal standards in acetonitrile. Chromatographic separations were achieved on an Aquity UPLC(®) BEH C(18) 1.7 μm 2.1 mm x 100mm column eluted at a flow-rate of 0.250 ml/min on a gradient of acetonitrile. The overall cycle time of the method was 7 min, with elution times of 1.3min for DX and 3HM, 2.8 min for 3MM and 2.9min for DM. The multiple reaction monitoring transitions were set at 272>215 (m/z), at 258>133 (m/z), at 258>213 (m/z) and at 244>157 (m/z) for DM, DX, 3MM and 3HM, respectively. The calibration curves were linear (r²≥0.995) over the range of 0.500-100 nM with the lower limit of quantitation validated at 0.500 nM for all compounds, which is equivalent to 136, 129, 129 and 122 pg/ml for DM, DX, 3MM and 3HM, respectively. Extraction recoveries were constant, but ranged from 39% for DM to 83% for DX. The within-run and between-run precisions were within 11.6%, while the accuracy ranged from 92.7 to 110.6%. The applicability of the bioanalytical method was demonstrated and is currently implemented in a clinical trial to study DM as probe-drug for individualized tamoxifen treatment in breast cancer patients.

Automated sample preparation for regulated bioanalysis: an integrated multiple assay extraction platform using robotic liquid handling

Background: A novel approach for regulated bioanalytical sample preparation has been developed to combine multiple types of extraction techniques into one integrated and automated sample-preparation suite that pairs a graphical user interface with the Hamilton Microlab® STAR robotic liquid handler. Results: The multi-assay sample-preparation suite is composed of three bioanalytical extraction techniques: protein precipitation, solid-phase extraction and liquid–liquid extraction. Validation data provided highly reproducible and robust results for each respective automated extraction technique. Conclusion: The user-friendly graphical user interface and modular method design provide a flexible and versatile approach for routine bioanalytical sample-preparation and is the first fully integrated multiple assay sample-preparation suite for regulated bioanalysis.

Desorption Atmospheric Pressure Photoionization

An ambient ionization technique for mass spectrometry, desorption atmospheric pressure photoionization (DAPPI), is presented, and its application to the rapid analysis of compounds of various polarities on surfaces is demonstrated. The DAPPI technique relies on a heated nebulizer microchip delivering a heated jet of vaporized solvent, e.g., toluene, and a photoionization lamp emitting 10-eV photons. The solvent jet is directed toward sample spots on a surface, causing the desorption of analytes from the surface. The photons emitted by the lamp ionize the analytes, which are then directed into the mass spectrometer. The limits of detection obtained with DAPPI were in the range of 56-670 fmol. Also, the direct analysis of pharmaceuticals from a tablet surface was successfully demonstrated. A comparison of the performance of DAPPI with that of the popular desorption electrospray ionization method was done with four standard compounds. DAPPI was shown to be equally or more sensitive especially in the case of less polar analytes.