Simultaneous Determination of Selegiline, Desmethylselegiline, R/S-methamphetamine, and R/S-amphetamine on Dried Urine Spots by LC/MS/MS: Application to a Pharmacokinetic Study in Urine

Biological Fluid Microsampling for Therapeutic Drug Monitoring: A Narrative Review

Therapeutic drug monitoring (TDM) is a specialized area of laboratory medicine which involves the measurement of drug concentrations in biological fluids with the aim of optimizing efficacy and reducing side effects, possibly modifying the drug dose to keep the plasma concentration within the therapeutic range. Plasma and/or whole blood, usually obtained by venipuncture, are the "gold standard" matrices for TDM. Microsampling, commonly used for newborn screening, could also be a convenient alternative to traditional sampling techniques for pharmacokinetics (PK) studies and TDM, helping to overcome practical problems and offering less invasive options to patients. Although technical limitations have hampered the use of microsampling in these fields, innovative techniques such as 3-D dried blood spheroids, volumetric absorptive microsampling (VAMS), dried plasma spots (DPS), and various microfluidic devices (MDS) can now offer reliable alternatives to traditional samples. The application of microsampling in routine clinical pharmacology is also hampered by the need for instrumentation capable of quantifying analytes in small volumes with sufficient sensitivity. The combination of microsampling with high-sensitivity analytical techniques, such as liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), is particularly effective in ensuring high accuracy and sensitivity from very small sample volumes. This manuscript provides a critical review of the currently available microsampling devices for both whole blood and other biological fluids, such as plasma, urine, breast milk, and saliva. The purpose is to provide useful information in the scientific community to laboratory personnel, clinicians, and researchers interested in implementing the use of microsampling in their routine clinical practice.

Dried Urine Spot Analysis for assessing cardiovascular drugs exposure applicable in spaceflight conditions

Cardiovascular pharmacological countermeasures will be required as a preventive measure of cardiovascular deconditioning and early vascular ageing for long term space travelers. Physiological changes during spaceflight could have severe implications on drug pharmacokinetics and pharmacodynamics (PK/PD). However, limitations exist for the implementation of drug studies due to the requirements and constraints of this extreme environment. Therefore, we developed an easy sampling method on dried urine spot (DUS), for the simultaneous quantification of 5 antihypertensive drugs in human urine: irbesartan, valsartan, olmesartan, metoprolol and furosemide analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), considering spaceflight parameters. This assay was validated in terms of linearity, accuracy, and precision with satisfactory results. There were no relevant carry-over, matrix interferences. The targeted drugs were stable in urine collected by DUS until 6 months at +21 °C, +4°C, -20 °C (with or without desiccants) and at 30 °C during 48 h. Irbesartan, valsartan and olmesartan were not stable at 50 °C during 48 h. This method was found to be eligible for space pharmacology studies in terms of practicality, safety, robustness and energy costs. It has been successfully implemented in space tests programs led in 2022.

In-vial dried urine spot collection and processing for quantitative analyses

Analysis of dried urine spots (DUSs) is becoming an emerging technique in clinical, toxicological, and forensic chemistry due to the fully non-invasive collection, facile transportation, and simple storage of DUS samples. Correct DUS collection and elution is of the utmost importance because inadequate DUS sampling/processing may have direct consequences on quantitative DUS analyses and these aspects were, for the first time, comprehensively investigated in this contribution. Various groups of endogenous and exogenous species were selected as model analytes and their concentrations were monitored in DUSs collected on standard cellulose-based sampling cards. Strong chromatographic effects were observed for most analytes having a crucial impact on their distribution within the DUSs during sampling. Concentrations of target analytes were up to 3.75-fold higher in the central DUS sub-punch in comparison to the liquid urine. Consequently, substantially reduced concentrations of these analytes were determined in peripheral DUS sub-punches demonstrating that sub-punching, often applied to dried material spots, is not acceptable for quantitative DUS analyses. Hence, a simple, rapid, and user-friendly procedure was suggested, which employed an in-vial collection of a known urine volume on a pre-punched sampling disc (using a low-cost micropipette designed for patient-centric clinical sampling) and in-vial processing of the whole DUS. Excellent accuracy (0.20%) and precision (0.89%) of liquid transfers were achieved by the micropipette, which was also applied to remote DUS collection by laic and expert users. The resulting DUS eluates were analysed by capillary electrophoresis (CE) for the determination of endogenous urine species. The CE results demonstrated no significant differences between the two user groups, elution efficiencies of 88-100% (in comparison to the liquid urine), and precision better than 5.5%.

Potential use of a dried saliva spot (DSS) in therapeutic drug monitoring and disease diagnosis

In recent years, scientific researchers have increasingly become interested in noninvasive sampling methods for therapeutic drug monitoring and disease diagnosis. As a result, dried saliva spot (DSS), which is a sampling technique for collecting dried saliva samples, has been widely used as an alternative matrix to serum for the detection of target molecules. Coupling the DSS method with a highly sensitive detection instrument improves the efficiency of the preparation and analysis of biological samples. Furthermore, dried blood spots, dried plasma spots, and dried matrix spots, which are similar to those of the DSS method, are discussed. Compared with alternative biological fluids used in dried spot methods, including serum, tears, urine, and plasma, saliva has the advantage of convenience in terms of sample collection from children or persons with disabilities. This review aims to provide integral strategies and guidelines for dried spot methods to analyze biological samples by illustrating several dried spot methods. Herein, we summarize recent advancements in DSS methods from June 2014 to March 2021 and discuss the advantages and disadvantages of the key aspects of this method, including sample preparation and method validation. Finally, we outline the challenges and prospects of such methods in practical applications.

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.

Recent advances in chiral analysis for biosamples in clinical research and forensic toxicology

This article covers current methods and applications in chiral analysis from 2010 to 2020 for biosamples in clinical research and forensic toxicology. Sample preparation for aqueous and solid biological samples prior to instrumental analysis were discussed in the article. GC, HPLC, capillary electrophoresis and sub/supercritical fluid chromatography provide the efficient tools for chiral drug analysis coupled to fluorescence, UV and MS detectors. The application of chiral analysis is discussed in the article, which involves differentiation between clinical use and drug abuse, pharmacokinetic studies, pharmacology/toxicology evaluations and chiral inversion. Typical chiral analytes, including amphetamines and their analogs, anesthetics, psychotropic drugs, β-blockers and some other chiral compounds, are also reviewed.

A review of recent advances in microsampling techniques of biological fluids for therapeutic drug monitoring

Conventional sampling of biological fluids often involves a bulk quantity of samples that are tedious to collect, deliver and process. Miniaturized sampling approaches have emerged as promising tools for sample collection due to numerous advantages such as minute sample size, patient friendliness and ease of shipment. This article reviews the applications and advances of microsampling techniques in therapeutic drug monitoring (TDM), covering the period January 2015 - August 2020. As whole blood is the gold standard sampling matrix for TDM, this article comprehensively highlights the most historical microsampling technique, the dried blood spot (DBS), and its development. Advanced developments of DBS, ranging from various automation DBS, paper spray mass spectrometry (PS-MS), 3D dried blood spheroids and volumetric absorptive paper disc (VAPD) and mini-disc (VAPDmini) are discussed. The volumetric absorptive microsampling (VAMS) approach, which overcomes the hematocrit effect associated with the DBS sample, has been employed in recent TDM. The sample collection and sample preparation details in DBS and VAMS are outlined and summarized. This review also delineates the involvement of other biological fluids (plasma, urine, breast milk and saliva) and their miniaturized dried matrix forms in TDM. Specific features and challenges of each microsampling technique are identified and comparison studies are reviewed.