A tandem mass spectrometry assay for the simultaneous determination of acetaminophen, caffeine, phenytoin, ranitidine, and theophylline in small volume pediatric plasma specimens

Evaluation and clinical application of a bracketing calibration-based isotope dilution liquid chromatography-tandem mass spectrometry candidate reference measurement procedure for serum theophylline

A candidate reference measurement procedure (RMP) for serum theophylline via isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. With a single-step precipitation pretreatment and a 6-min gradient elution, the method achieved baseline separation of theophylline and its analogs on a C18-packed column. A bracketing calibration method was used to ensure repeatable signal intensity and high measurement precision. The intra-assay and inter-assay imprecisions were 1.06%, 0.84%, 0.72% and 0.47%, 0.41%, 0.25% at concentrations of 4.22 µg/mL (23.40 µmol/L), 8.45 µg/mL (46.90 µmol/L), and 15.21 µg/mL (84.43 µmol/L), respectively. Recoveries ranged from 99.35 to 102.34%. The limit of detection (LoD) was 2 ng/mL, and the lowest limit of quantification (LLoQ) was 5 ng/mL. The linearity range extended from 0.47 to 60 µg/mL (2.61-333.04 µmol/L). No ion suppression and carry-over (< 0.68%) were observed. The relative bias for this candidate RMP that participated in 2023 External Quality Control for Reference Laboratories (RELA) conducted by the International Federation of Clinical Chemistry (IFCC) was within a range of 0.17 to 0.93%. Furthermore, two clinical immunoassay systems were compared with this candidate RMP, demonstrating good correlations. The results of the Trueness Verification Plan indicate significant differences among routine systems, highlighting the need for standardization efforts. The developed candidate RMP for serum theophylline serves as a precise reference baseline for standardizing clinical systems and assigning values to reference materials.

Caffeine pharmacokinetics following umbilical vein injection during delayed cord clamping in preterm lambs

BACKGROUND

Spontaneous breathing during and after delayed cord clamping (DCC) stabilizes cardiopulmonary transition at birth. Caffeine stimulates breathing and decreases apnea in premature newborns. We evaluated the pharmacokinetics and physiological effects of early caffeine administration-direct injection into the umbilical vein (UV) during DCC or administered through a UV catheter (UVC) after delivery.

METHODS

Eighteen extremely premature lambs (125-127d, term gestation 145d) were exteriorized and instrumented. Lambs received caffeine-citrate at high (40 mg/kg) or standard-dose (20 mg/kg) via direct UV (DUV) injection during DCC, or via the UVC.

RESULTS

Mean peak plasma caffeine concentrations were lower with high-dose DUV compared to UVC (18 ± 4.3 vs. 46 ± 12 mg/L, p < 0.05). With standard-dose caffeine, mean peak plasma levels were 7.48 ± 2.6 with DUV and 28.73 ± 9.4 mg/L with UVC. The volume of distribution was higher in the DUV group compared to UVC (2.5 ± 1.0 vs. 0.69 ± 0.15 L/kg) with an estimated 39 ± 18% entering the maternal circulation. Maternal peak concentrations were 0.79 ± 0.71 and 1.43 ± 0.74 mg/L with standard and high-dose DUV, respectively.

CONCLUSIONS

Caffeine injected directly into the UV during DCC is feasible but achieves lower concentrations due to high volume of distribution including maternal circulation. Further trials evaluating DUV caffeine injection should use higher caffeine doses.

IMPACT

Respiratory stimulation with early caffeine may reduce the need for intubation in preterm infants. In the preterm lambs, caffeine injection directly into the umbilical vein during delayed cord clamping is feasible. Plasma caffeine concentrations are less than half when administered directly into the umbilical vein during delayed cord clamping compared to administration via an umbilical venous catheter following birth likely attributed to a larger volume of distribution or injection site leak. There were no significant hemodynamic alterations following caffeine injection.

GC Analysis of Metformin, Ranitidine and Famotidine from Pharmaceuticals and Human Serum

A method has been designed based on gas chromatography with flame ionization detection (FID) for the separation and analyses of ranitidine, famotidine and metformin after pre-column derivatization with trifluoroacetylacetone and ethyl chloroformate. DB-1 (30 m × 0.32 mm id) column with film thickness 0.25 μm was used for the separation at an initial temperature of column was 100°C for 2 min, and ramping at 20°C/min up to 250°C, with a hold time of 3 min. The rate of nitrogen flow was 2.5 mL/min and FID was used for detection. Complete separation was obtained between all the three drugs including excess of derivatization reagents. Linear calibration curves and detection limits were obtained in the ranges 0.1-30 μg/mL and 0.011-0.015 μg/mL. The procedure was repeatable in terms of peak heights/peak areas and retention time (n = 5) for derivatization, quantitation and separation with relative standard deviations (RSDs) within 2.0-3.0%. The approach was examined for the analyses of drug products and serum after the intake of the drugs by healthy volunteers, and recoveries were obtained within 95-98% with RSDs 2.4-3.1%.

An effective and stability-indicating method development and optimization utilizing the Box-Behnken design for the simultaneous determination of acetaminophen, caffeine, and aspirin in tablet formulation

Analytical techniques must be sensitive, specific, and accurate to assess the active pharmaceutical ingredients in pharmaceutical dosage forms. The quality-by-design (QbD) application has proven to be a practical method for magnifying HPLC operations. This article discusses the successfully developed QbD-based stability-indicative LC method for evaluating acetaminophen, caffeine, and aspirin (ASP) in tablet dosage form. To achieve the necessary chromatographic separation, Milli-Q water, methanol, and glacial acetic acid were employed in the following ratios: 63:35:2 (v/v/v) for mobile phase A and 18:80:2 (v/v/v) for mobile phase B. The flow rate, column temperature, and detecting wavelength were 1.0 ml/min, 40°C, and 275 nm, respectively, and an InertSustain C18 analytical column (150 × 4.6 mm, 3 μm) was used. Linearity was between 10.0 and 150.0 μg/ml for ASP and acetaminophen and between 2.6 and 39.0 μg/ml for caffeine. The accuracy findings were more than 97%, and the correlation coefficient for all three components was found to be greater than 0.999. The validated HPLC method yielded reliable and accurate results. ASP was shown to be vulnerable to both acid and alkaline hydrolysis in the forced degradation study. The described method is capable of separating the degradants produced during stress testing and is regarded as stability indicating. The proposed method can be used for a wider range of other formulations with an appropriate diluent selection and sample preparation procedure optimization.

Determination of caffeine, paraxanthine, theophylline and theobromine in premature infants by HILIC-MS/MS

Aim: Caffeine is a central nervous system stimulant, used to treat apnea of prematurity. A hydrophilic interaction chromatography-tandem mass spectrometry (HILIC-MS/MS) approach was developed to detect caffeine, paraxanthine, theophylline and theobromine in premature infants. Method: Protein precipitation of plasma samples (10 μl) was carried out by treating with acetonitrile containing caffeine-¹³C₃. The separation was carried out on an ACQUITY HPLC^® BEH HILIC column. Caffeine and its metabolites were quantified by multiple reaction monitoring modes with positive electrospray ionization. Results: The established method had a good linear relationship in the range of 0.0600-60.0 μg/ml for caffeine, 0.0250-7.50 μg/ml for theobromine and 0.0150-4.50 μg/ml for paraxanthine and theophylline. Conclusion: A HILIC-MS/MS method was developed and validated to determine caffeine and its major metabolites in plasma of premature infants.

A sensitive LC-MS/MS method for quantification of phenytoin and its major metabolite with application to in vivo investigations of intravenous and intranasal phenytoin delivery

Phenytoin is a powerful antiseizure drug with complex pharmacokinetic properties, making it an interesting model drug to use in preclinical in vivo investigations, especially with regards to formulations aiming to improve drug delivery to the brain. Moreover, it has a major metabolite, 5‐(4‐hydroxyphenyl)‐5‐phenylhydantoin, which can be simultaneously studied to achieve a better assessment of its behaviour in the body. Here, we describe the development and validation of a sensitive LCMS/MS method for quantification of phenytoin and 5‐(4‐hydroxyphenyl)‐5‐phenylhydantoin in rat plasma and brain which can be used in such preclinical studies. Calibration curves produced covered a range of 7.81 to 250 ng/mL (plasma) and 23.4 to 750 ng/g (brain tissue) for both analytes. The method was validated for specificity, sensitivity, accuracy, and precision and found to be within the acceptable limits of ±15% over this range in both tissue types. The method when applied in two in vivo investigations: validation of a seizure model and to study the behaviour of a solution of intranasally administered phenytoin as a foundation for future studies into direct nose‐to‐brain delivery of phenytoin using specifically developed particulate systems, was highly sensitive for detecting phenytoin and 5‐(4‐hydroxyphenyl)‐5‐phenylhydantoin in rat plasma and brain.

Developing a SWATH capillary LC-MS/MS method for simultaneous therapeutic drug monitoring and untargeted metabolomics analysis of neonatal plasma

Most medications prescribed to neonatal patients are off-label uses. The pharmacokinetics and pharmacodynamics of drugs differ significantly between neonates and adults. Therefore, personalized pharmacotherapy guided by therapeutic drug monitoring (TDM) and drug response biomarkers are particularly beneficial to neonatal patients. Herein, we developed a capillary LC-MS/MS metabolomics method using a SWATH-based data-independent acquisition strategy for simultaneous targeted and untargeted metabolomics analysis of neonatal plasma samples. We applied the method to determine the global plasma metabolomics profiles and quantify the plasma concentrations of five drugs commonly used in neonatal intensive care units, including ampicillin, caffeine, fluconazole, vancomycin, and midazolam and its active metabolite α-hydroxymidazolam, in neonatal patients. The method was successfully validated and found to be suitable for the TDM of the drugs of interest. Moreover, the global metabolomics analysis revealed plasma metabolite features that could differentiate preterm and full-term neonates. This study demonstrated that the SWATH-based capillary LC-MS/MS metabolomics approach could be a powerful tool for simultaneous TDM and the discovery of neonatal plasma metabolite biomarkers.

High performance liquid chromatography: A versatile tool for assaying antiepileptic drugs in biological matrices

Epilepsy is a recurrent long-term illness occurring in approximately 1.0% of the world's population. There are currently about 29 approved antiepileptic drugs for the management of epilepsy. Due to narrow therapeutic indices of most antiepileptic drugs, clinical pharmacokinetic characteristics and therapeutic drug monitoring of these drugs are imperative. The objectives of this review were to identify common chromatographic principles, requirements and/or conditions for high-performance liquid chromatography as applied to assay of antiepileptic drugs in biological matrices. The review was conducted using 66 peer reviewed articles (1990 to 2020) from 29 journals that were sought via PubMed, Science Direct and Google Scholar. In all, 29 antiepileptic drugs were assayed from 6 different biological matrices. Forty-three of the reviewed articles estimated the concentration of only one antiepileptic drug, whilst 23 articles focused on simultaneous determination of two or more antiepileptic drugs. Thirty-four, 20, and 14 articles reported using liquid-liquid extraction, protein precipitation, or solid phase extraction for sample clean up, respectively. The ratio of reversed-phase to normal phase, LC-UV to LC-MS and isocratic elution to gradient elution were 61:3, 43:7 and 55:11, respectively. With the exception of one article the reported recoveries ranged from 60.3% to 109.6%. It is noteworthy, that, the performance metrics of high-performance liquid chromatography are better compared to other assays of antiepileptic drugs in biological matrices. This review describes the relevant liquid chromatographic method conditions over the past 30 years for the analysis of this class of drugs, which provides a basis for further method development and optimization.

Rapid and Simultaneous Analysis of Multiple Classes of Antimicrobial Drugs by Liquid Chromatography-Tandem Mass Spectrometry and Its Application to Routine Biomedical, Food, and Soil Analyses

Antimicrobial agents (AMAs) are widely exploited nowadays to meet the high demand for animal-derived food. It has a significant impact on the food chain whose end consumers are human beings. The burden of AMAs on humans comes from either meat or crops cultivated on soil containing high residual antibiotics, which are responsible for the global crisis of antibiotic resistance. Thus, the objective of this study was to design a selective and sensitive liquid chromatography-mass spectrometry (LC-MS)/MS-based simultaneous bioanalytical method for estimation of twenty AMAs in human plasma, raw meat, and soil samples. The selective extraction of all analytes from the above matrices was performed by the solid-phase extraction clean-up method to overcome the interferences. Analytes were separated on a Waters Symmetry Shield C18 (150 × 4.6 mm², 5 μm) column, using an isocratic solvent system of methanol-0.5% formic acid (80:20, v/v) with 0.75 mL/min flow rate. The average extraction recoveries for all analytes in plasma were ranged from 42.0 to 94.0% with relative standard deviations (RSDs) below ±15%. All of the validation parameters are in accordance with the United State Food and Drug Administration (USFDA) guidelines. Moreover, the method was also valid for a broad plasma concentration range and can be proposed as an excellent method for routine pharmacokinetic studies, therapeutic drug monitoring, clinical analysis, and detection and quantitation of AMA remnants in raw meat as a standard quality control test for human consumption.

Natural Perspiration Sampling and in Situ Electrochemical Analysis with Hydrogel Micropatches for User-Identifiable and Wireless Chemo/Biosensing

Recent advances in microelectronics, microfluidics, and electrochemical sensing platforms have enabled the development of an emerging class of fully integrated personal health monitoring devices that exploit sweat to noninvasively access biomarker information. Despite such advances, effective sweat sampling remains a significant challenge for reliable biomarker analysis, with many existing methods requiring active stimulation (e.g., iontophoresis, exercise, heat). Natural perspiration offers a suitable alternative as sweat can be collected with minimal effort on the part of the user. To leverage this phenomenon, we devised a thin hydrogel micropatch (THMP), which simultaneously serves as an interface for sweat sampling and a medium for electrochemical sensing. To characterize the performance of the THMP, caffeine and lactate were selected as two representative target molecules. We demonstrated the suitability of the sampling method to track metabolic patterns, as well as to render sample-to-answer biomarker data for personal monitoring (through coupling with an electrochemical sensing system). To inform its potential application, this biomarker sampling and sensing system is incorporated within a distributed terminal-based sensing network, which uniquely capitalizes on the fingertip as a site for simultaneous biomarker data sampling and user identification.

An Introduction to Drug Testing: The Expanding Role of Mass Spectrometry

Measurement of drugs and their metabolites in biological fluids is the foundation of both therapeutic drug monitoring (TDM) and toxicology. The introduction of methods based on mass spectrometry (MS), coupled with gas or liquid chromatography, has revolutionized these areas. This chapter will introduce the reader to the application of MS to TDM and toxicology, the steps that should be considered during implementation and the processes that should be implemented to assure continued quality. Points of emphasis include advances and recent trends since the publication of the first edition of this book, such as high-resolution mass spectrometry and increased interest in alternate matrices.

Quantitation of paracetamol by liquid chromatography-mass spectrometry in human plasma in support of clinical trial

Aim:

Paracetamol is a well-tolerated antipyretic widely used in severe malaria management. The study aimed to develop and validate a rapid LC–MS/MS assay to quantify paracetamol in plasma from patients with severe malaria.

Materials & methods:

Plasma sample was precipitated by organic solvent containing isotope-labeled paracetamol internal standard. Supernatant was isolated, diluted with water, followed by LC–MS/MS analysis.

Results:

Plasma samples were extracted and assayed in less than 5.5 min. The assay response was linear (0.125–50 mg/l) with total intra- and interassay imprecision of <1.4%, which were considerably lower than most published reports.

Conclusion:

We developed, validated and applied a rapid and small volume LC–MS/MS assay with high precision and accuracy for plasma paracetamol quantitation in 989 samples from 62 patients with severe malaria. The simple and high-throughput quality could facilitate assay automation for future clinical studies.

Paracetamol is a commonly prescribed antipyretic in severe malaria management. Here, a rapid quantitative assay was developed to measure the plasma level of paracetamol. The developed method required levels as low as 20 μl plasma, and was highly precise, with a short analysis time of 5.5 min. The developed method is particularly suitable for clinical trial application and potentially for clinical use.

Innovative Study Designs Optimizing Clinical Pharmacology Research in Infants and Children

Almost half of recent pediatric trials failed to achieve labeling indications, in large part because of inadequate study design. Therefore, innovative study methods are crucial to optimizing trial design while also reducing the potential harms inherent with drug investigation. Several methods exist to optimize the amount of pharmacokinetic data collected from the smallest possible volume and with the fewest number of procedures, including the use of opportunistic and sparse sampling, alternative and noninvasive matrices, and microvolume assays. In addition, large research networks using master protocols promote collaboration, reduce regulatory burden, and increase trial efficiency for both early- and late-phase trials. Large pragmatic trials that leverage electronic health records can capitalize on central management strategies to reduce costs, enroll patients with rare diseases on a large scale, and augment study generalizability. Further, trial efficiency and safety can be optimized through Bayesian adaptive techniques that permit planned protocol changes based on analyses of prior and accumulated data. In addition to these trial design features, advances in modeling and simulation have paved the way for systems-based and physiologically based models that individualize pediatric dosing recommendations and support drug approval. Last, given the low prevalence of many pediatric diseases, collecting deidentified genetic and clinical data on a large scale is a potentially transformative way to augment clinical pharmacology research in children.

Simultaneous determination of acetaminophen, pramipexole and carbamazepine by ZSM-5 nanozeolite and TiO2 nanoparticles modified carbon paste electrode

In this present paper, a simple voltammetric method has been reported for the simultaneous determination of acetaminophen (AC), pramipexole (PRX) and carbamazepine (CBZ) using ZSM-5 nanozeolite-TiO₂ nanoparticles composite modified carbon paste electrode (ZSM-5/TiO₂/CPE). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and N₂ adsorption-desorption isotherm were used to characterize the structure of synthesized ZSM-5 nanozeolite. Also, cyclic voltammetry (CV), choronoamperometry and differential pulse voltammetry (DPV) were used to investigate the performance of the modified electrode. The oxidation peak currents of AC, PRX and CBZ at the surface of ZSM-5/TiO₂/CPE were increased dramatically against CPE and their overpotentials decreased. Also, DPV method was used for the simultaneous determination of three drugs in ternary mixture. The effects of modifier amount, pH and scan rate were investigated on the electrochemical response of AC, PRX and CBZ oxidation. The diffusion coefficient, D, and the catalytic rate constant, k_cat, were estimated for the oxidation of AC, PRX and CBZ at the surface of modified electrode. Under the optimized experimental conditions, AC, PRX and CBZ give linear response over the range of 2.5-110, 0.6-105 and 6.0-97 μM, respectively. The detection limits were found to be 0.58, 0.38 and 1.04 μM (S/N = 3) for AC, PRX and CBZ, respectively. The fabricated electrode showed good stability, reproducibility and repeatability as well as high recovery. The practical application of the modified electrode was demonstrated by measuring the concentration of spiked AC, PRX and CBZ in human plasma as real sample. The proposed method is simple, rapid and inexpensive and can be utilized as a valuable analytical tool in quality control of the pharmaceutical industry.

The Pocket-4-Life project, bioavailability and beneficial properties of the bioactive compounds of espresso coffee and cocoa-based confectionery containing coffee: study protocol for a randomized cross-over trial

Background

Coffee is an important source of bioactive compounds, including caffeine, phenolic compounds (mainly chlorogenic acids), trigonelline, and diterpenes. Several studies have highlighted the preventive effects of coffee consumption on major cardiometabolic diseases, but the impact of coffee dosage on markers of cardiometabolic risk is not well understood. Moreover, the pool of coffee-derived circulating metabolites and the contribution of each metabolite to disease prevention still need to be evaluated in real-life settings. The aim of this study will be to define the bioavailability and beneficial properties of coffee bioactive compounds on the basis of different levels of consumption, by using an innovative experimental design. The contribution of cocoa-based products containing coffee to the pool of circulating metabolites and their putative bioactivity will also be investigated.

Methods

A three-arm, crossover, randomized trial will be conducted. Twenty-one volunteers will be randomly assigned to consume three treatments in a random order for 1 month: 1 cup of espresso coffee/day, 3 cups of espresso coffee/day, and 1 cup of espresso coffee plus 2 cocoa-based products containing coffee twice per day. The last day of each treatment, blood and urine samples will be collected at specific time points, up to 24 hours following the consumption of the first product. At the end of each treatment the same protocol will be repeated, switching the allocation group. Besides the bioavailability of the coffee/cocoa bioactive compounds, the effect of the coffee/cocoa consumption on several cardiometabolic risk factors (anthropometric measures, blood pressure, inflammatory markers, trimethylamine N-oxide, nitric oxide, blood lipids, fasting indices of glucose/insulin metabolism, DNA damage, eicosanoids, and nutri-metabolomics) will be investigated.

Discussion

Results will provide information on the bioavailability of the main groups of phytochemicals in coffee and on their modulation by the level of consumption. Findings will also show the circulating metabolites and their bioactivity when coffee consumption is substituted with the intake of cocoa-based products containing coffee. Finally, the effect of different levels of 1-month coffee consumption on cardiometabolic risk factors will be elucidated, likely providing additional insights on the role of coffee in the protection against chronic diseases.

Trial registration

ClinicalTrials.gov, NCT03166540. Registered on May 21, 2017.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2271-2) contains supplementary material, which is available to authorized users.

Simultaneous determination of pentoxifylline, metabolites M1 (lisofylline), M4 and M5, and caffeine in plasma and dried blood spots for pharmacokinetic studies in preterm infants and neonates

Advances in bioanalytical methods are facilitating micro-volume and dried blood spot (DBS) analysis of drugs in biological matrices for pharmacokinetic studies in children and neonates. We sought to develop a UPLC-MS/MS assay for simultaneous measurement of caffeine, pentoxifylline (PTX) and three metabolites of PTX in both plasma and DBS. Caffeine, PTX, the metabolites M1 (lisofylline), M4 and M5, and the internal standards (caffeine-d₉ and PTX-d₆) were separated using a Waters Aquity T3 UPLC C₁₈ column and gradient mobile phase (water-methanol-formic acid). Retention times for caffeine, M5, M4, PTX and M1 were 1.6, 1.7, 1.9, 2.0 and 2.1min, respectively, with a run time of 5min. The precision (≤10%) and accuracy (≤15%) across the concentration range 0.1-50mg/L for caffeine, PTX and the three metabolites in plasma and DBS were within accepted limits, as were the limits of quantification (100μg/L for caffeine and 10μg/L for PTX, M1, M4 and M5). Caffeine, PTX and the metabolites were stable in DBS for >34days at room and refrigerated temperatures. Plasma and DBS samples were obtained from 24 preterm infants recruited into a clinical pharmacokinetic study of PTX. Paired analysis indicated that DBS concentrations were 9% lower than concurrent plasma concentrations for caffeine, 7% lower for PTX (consistent with the blood:plasma ratio) and 13% lower for M1 (lisofylline). The validated UPLC-MS/MS method is suitable for micro-volume plasma and DBS analysis of caffeine, PTX and its metabolites for pharmacokinetic studies in paediatric patients.

Resolution and quantification challenge of modern chemometric models in the determination of anti-migraine tablets containing ergotamine, caffeine, acetaminophen, and metoclopramide

Unique mixture of ergotamine (ERG), metoclopramide (MET), caffeine (CAF) and the study presents a comparison between five multivariate models in the determination of the paracetamol (PAR) in laboratory mixtures and in pharmaceutical formulations.

Pharmacokinetics of ranitidine in preterm and term neonates with gastroesophageal reflux

Background

The aim of this study was to determine the effect of gestational age on pharmacokinetics of ranitidine in newborns with gastroesophageal reflux.

Methods

A prospective, descriptive and pharmacokinetic study was carried out in 30 pre-term and 20 full-term babies. 3 mg/kg of ranitidine was administered intravenously to all the babies and at 0.25, 0.5, 1, 2, 4, and 8 h following the administration, samples of blood were drawn to assess ranitidine levels using high performance liquid chromatographic technique.

Results

Pharmacokinetics of ranitidine had a bi-exponential behavior with a half-life elimination of (t_1/2el) 2.79 h, area under curve (AUC) of 1688 ng/mL, volume of distribution (Vd) of 1.44 L/kg, and clearance (Cl) of 5.9 L/kg/h. The median plasmatic concentration in pre-terms was 1113 ng/mL and 280 ng/mL in full-terms. Vd, t1/2 and Cl presented high values in preterm although the correlation of Cl with glomerular filtration in term newborns was better.

Conclusions

Plasma levels of ranitidine depend on the gestational age of the newborns. However, the possible relationship between after-birth age and pharmacokinetics of the neonates as their internal organs get matured without minding their gestational background.

Simultaneous quantitation of acetylsalicylic acid and clopidogrel along with their metabolites in human plasma using liquid chromatography tandem mass spectrometry

The interest in therapeutic drug monitoring has increased over the last few years. Inter- and intra-patient variability in pharmacokinetics, plasma concentration related toxicity and success of therapy have stressed the need of frequent therapeutic drug monitoring of the drugs. A sensitive, selective and rapid liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous quantification of acetylsalicylic acid (aspirin), salicylic acid, clopidogrel and carboxylic acid metabolite of clopidogrel in human plasma. The chromatographic separations were achieved on Waters Symmetry Shield(TM) C18 column (150 × 4.6 mm, 5 µm) using 3.5 mm ammonium acetate (pH 3.5)-acetonitrile (10:90, v/v) as mobile phase at a flow rate of 0.75 mL/min. The present method was successfully applied for therapeutic drug monitoring of aspirin and clopidogrel in 67 patients with coronary artery disease.

Effect of metoclopramide on the excretion rate of paracetamol using HPLC-DAD

A simple, precise, accurate and robust high-performance liquid chromatography assay was developed and validated for the simultaneous analysis of metoclopramide and paracetamol in human urine. The drugs were isolated from urine samples by solid-phase extraction using C8 cartridges, then analyzed on a C18 reversed-phase column using a mixture of aqueous phase (water containing 0.2% TEA adjusted to pH 3 using ortho-phosphoric acid) and methanol in a ratio of 80:20 (v/v). The method was found to be linear for both drugs in a concentration range of 0.5 to 160 µg/mL using a concentration of 10 µg/mL of internal standard (theophylline) in urine samples (r > 0.999). The accuracy of the method was higher than 91.73% (percentage of the grand mean of recoveries) and the precision was lower than 3.4% (overall percentage of relative standard deviation) for both metoclopramide and paracetamol. The method was applied to the determination of the drugs in urine samples obtained from male volunteers, following the administration of two formulations, one containing paracetamol alone (Paracetamol(®)) and the other containing a mixture of paracetamol and metoclopramide (Migracicid(®)). Determination of the drugs was conducted and the effect of increasing the rate of absorption, consequently increasing the mean urinary excretion of paracetamol due to the presence of metoclopramide in the pharmaceutical formulation, was recorded.

An introduction to drug testing: the expanding role of mass spectrometry

Measurement of drugs and their metabolites in biological fluids is the foundation of both therapeutic drug monitoring (TDM) and toxicology. Though different in their application, each discipline depends upon accurate identification and quantification if the measurements are to be useful. Thousands of methods are described for drug analysis but until recently most have relied upon analytical tools, such as spectrophotometry and immunoassay, that suffer from lack of specificity and sensitivity. The introduction of methods based on mass spectrometry (MS), coupled to gas or liquid chromatography, has revolutionized these areas. The methods are proving to be robust, versatile, and economical. This chapter introduces the reader to the application of MS to TDM and toxicology, the steps that should be considered during implementation, and the processes that should be implemented to assure continued quality.

Analysis of alkaloids from different chemical groups by different liquid chromatography methods

Alkaloids are biologically active compounds widely used as pharmaceuticals and synthesised as secondary methabolites in plants. Many of these compounds are strongly toxic. Therefore, they are often subject of scientific interests and analysis. Since alkaloids — basic compounds appear in aqueous solutions as ionized and unionized forms, they are difficult for chromatographic separation for peak tailing, poor systems efficiency, poor separation and poor column-to-column reproducibility. For this reason it is necessity searching of more suitable chromatographic systems for analysis of the compounds. In this article we present an overview on the separation of selected alkaloids from different chemical groups by liquid chromatography thus indicating the range of useful methods now available for alkaloid analysis. Different selectivity, system efficiency and peaks shape may be achieved in different LC methods separations by use of alternative stationary phases: silica, alumina, chemically bonded stationary phases, cation exchange phases, or by varying nonaqueous or aqueous mobile phase (containing different modifier, different buffers at different pH, ion-pairing or silanol blocker reagents). Developments in TLC (NP and RP systems), HPLC (NP, RP, HILIC, ion-exchange) are presented and the advantages of each method for alkaloids analysis are discussed.

An HPLC-ESI-MS method for simultaneous determination of fourteen metabolites of promethazine and caffeine and its application to pharmacokinetic study of the combination therapy against motion sickness

The combination therapy, promethazine and caffeine had been proven effective in treating motion sickness and counteracting some possible side effects of using promethazine alone while the mechanism and interaction remained unclear. Therefore, an HPLC-ESI-MS method for simultaneous determination of both drugs, and their metabolites was developed for purpose of pharmacokinetic study. To determine as many metabolites as possible, the influence of parameters such as column, flow rate and pH value of mobile phase, ionization polarity and fragmentation voltage were optimized. Fourteen target analytes were well separated and all of them could be identified and determined in plasma after administration of promethazine and caffeine. The LODs and LOQs were 0.9-6.0 and 2.50-16.0 ng/ml, respectively; the recoveries of three levels of quality control samples were from 86.7% to 102%; the intra-day and inter-day precisions were less than 3% and 9%, separately; and the RSDs of compound stability were all lower than 10% within 24h after sample preparation. As a pharmacokinetic study of the combination therapy in 30 healthy volunteers, concentration-time curves of the drugs and metabolites were studied. The present method for simultaneous measurement of more than ten metabolites is valuable for the study of mechanism and interaction of the combination therapy.