Quantitation of atenolol, metoprolol, and propranolol in postmortem human fluid and tissue specimens via LC/APCI-MS

Application of UHPLC-QqQ-MS/MS Method for Quantification of Beta-Adrenergic Blocking Agents (β-Blockers) in Human Postmortem Specimens

Betablockers are one of the most frequently used medications in cardiology. They can lead to fatal drops in blood pressure and heart rhythm disturbances. Death is functional, and poisoning with this group of drugs can be difficult to detect. The liquid-liquid extraction (LLE) method developed using ethyl acetate at pH 9 successfully identified 18 β-blockers in human blood. The method's limit of quantification (LOQ) was in the range of 0.1 to 0.5 ng/mL. No carryover of substances between samples was detected, and no interfering ion current signals were observed in the biological samples at the retention times of the compounds or internal standards. All compounds had a coefficient of determination (R2) above 0.995. Intraday and interday precision (RSD%) and accuracy (RE%) for low and high QC levels were within 1.7-12.3% and -14.4 to 14.1%, respectively. Very good recovery (80.0-119.6%) and matrix effect (±20.0%) values were achieved for all compounds. In addition, fragmentation spectra were collected for all the examined substances, and high-resolution spectra were presented for landiolol and metipranolol, because they are not available in commercial HRMS spectra databases. The developed method was applied in authentic postmortem samples.

Development of a RP-HPLC method for simultaneous determination of atenolol, metoprolol tartrate and phenol red for in-situ rat intestinal perfusion studies

Single-pass intestinal perfusion (SPIP) method is a widely used experimental model to determine the intestinal permeability of drugs. These studies are performed in the presence of a reference standard (metoprolol, MT) and a zero permeability marker (phenol red, PR). Therefore, it is important to develop a validated method for simultaneous determination of the investigated compound along with MT and PR. The aim of this study was to develop a reversed phase high-performance liquid chromatography (RP-HPLC) method with UV-detection for the simultaneous determination of atenolol (ATN), MT, and PR in the perfusion medium used in SPIP experiments. Separation of compounds were performed using an InertSustain C18 (250 × 4.6 mm, 5 µm) HPLC column at 35 °C. The mobile phase was a mixture of acetonitrile and phosphate buffer (pH 7.0, 12.5 mM) in gradient elution, and was delivered at a flow rate of 1 mL/min. The acetonitrile ratio of the mobile phase increased linearly from 10 to 35 % over 15 min. The injection volume was 20 µL, and ATN, MT and PR were detected at 224 nm. The retention times under optimum HPLC conditions were 5.028 min, 12.401 min, and 13.507 min for ATN, MT and PR, respectively. The developed RP-HPLC method was validated for selectivity, specificity, calibration curve and range, accuracy and precision, carry-over effect, stability, reinjection reproducibility, recovery and robustness. The method was linear for ATN (0.76-50 μg/mL), MT (1.14-50 μg/mL), and PR (0.47-20 μg/mL) with determination coefficients of 0.9999, 0.9994 and 0.9998, respectively. The results obtained for all validation parameters of the developed RP-HPLC method met the required limits of the ICH M10 Guideline.

Further exploration of the collision-induced dissociation of select beta blockers: Acebutolol, atenolol, bisoprolol, carteolol, and labetalol

Beta blockers are a class of drugs commonly used to treat heart-related diseases; they are also regulated under the World Anti-Doping Agency. Tandem mass spectrometry is often used in the pharmaceutical industry, clinical analysis laboratory, and antidoping laboratory for detection and characterization of drugs and their metabolites. A deeper chemical understanding of dissociation pathways may eventually lead to an improved ability to predict tandem mass spectra of compounds based strictly on their chemical structure (or vice versa), which is especially important for characterization of unknowns such as emerging designer drugs or novel metabolites. In addition to providing insights into dissociation pathways, the use of energy-resolved breakdown curves can produce improved selectivity and lend insights into optimal fragmentation conditions for liquid chromatography-tandem mass spectrometry LC-MS/MS workflows. Here, we perform energy-resolved collision cell and multistage ion trap collision-induced dissociation-mass spectrometry (CID-MS) experiments, along with complementary density functional theory calculations, on five beta blockers (acebutolol, atenolol, bisoprolol, carteolol, and labetalol), to better understand the details of the pathways giving rise to the observed MS/MS patterns. Results from this work are contextualized within previously reported literature on these compounds. New insights into the formation of the characteristic product ion m/z 116 and the pathway leading to characteristic loss of 77 u are highlighted. We also present comparisons of breakdown curves obtained via qToF, quadrupole ion trap, and in-source CID, allowing for differences between the data to be noted and providing a step toward allowing for improved selectivity of breakdown curves to be realized on simple instruments such as single quadrupoles or ion traps.

A Novel Composite Voltammetric Sensor Based on Yttria-Stabilized Zirconia Doped with Neodymium-Carbon Black-Nafion Glassy Carbon Electrode for Metoprolol Determination

For the first time, a new composite voltammetric sensor based on yttria-stabilized zirconia doped with neodymium-carbon black-Nafion glassy carbon electrode (YSZNd-CB-Nafion/GCE) for the determination of metoprolol (MET) has been developed. The instrumental parameters and supporting electrolyte were optimized. For 105 s accumulation time, linearity was achieved in the range of 0.01 to 0.2 µM. The limit of detection (for 105 s accumulation time) was equal to 2.9 nM (2 µg/L), and was the best result in comparison to other voltametric sensors. The reproducibility of the metoprolol signal presented as relative standard deviation (RSD) was equal to 1.9% (n = 7). Additionally, our electrode is characterized by high stability, is easy to use, and has a short preparation time. The proposed sensor was found useful for MET determination in plasma and urine, as well as for pharmaceutical samples, with a good recovery parameter (96-108%). Flow injection analysis (FIA) with amperometric detection was also performed for MET determination. The recovery was calculated and was in the range 101-103%, suggesting that the proposed material may be applied in flow injection analysis.

Spatially confining copper nanoclusters in porous ZrO2 for fluorescence/colorimetry/smartphone triple-mode detection of metoprolol tartrate

Sensitive detection of metoprolol tartrate (MPT) is extremely urgent in the therapy of cardiovascular diseases to guarantee the curative effectiveness. Herein, porous ZrO₂ was first employed as a matrix to spatially confine CuNCs (ZrO₂@CuNCs), which simultaneously ameliorated the emission intensity and stability of CuNCs. Benefiting from the inner filter effect (IFE) and dynamic quenching effect (DQE) between ZrO₂@CuNCs and AuNPs and the color fading of AuNPs induced by MPT, fluorometric and colorimetric methods for simple and sensitive determination of MPT were proposed. Besides, to meet the demand of convenient detection of MPT, a portable sensing platform was constructed including a dark box produced by a 3D printer and a smartphone. This method was further employed to determine MPT in human serum and urine samples with satisfactory results with the triple mode. This work is the first attempt to fabricate a multi-mode optical and portable sensor for MPT detection, which provides a novel approach for point-of-care monitoring of drugs in the treatment of diseases.

Stochastic Dynamic Mass Spectrometric Quantitative and Structural Analyses of Pharmaceutics and Biocides in Biota and Sewage Sludge

Mass spectrometric innovations in analytical instrumentation tend to be accompanied by the development of a data-processing methodology, expecting to gain molecular-level insights into real-life objects. Qualitative and semi-quantitative methods have been replaced routinely by precise, accurate, selective, and sensitive quantitative ones. Currently, mass spectrometric 3D molecular structural methods are attractive. As an attempt to establish a reliable link between quantitative and 3D structural analyses, there has been developed an innovative formula [DSD″,tot=∑inDSD″,i=∑in2.6388.10-17×Ii2¯-Ii¯2] capable of the exact determination of the analyte amount and its 3D structure. It processed, herein, ultra-high resolution mass spectrometric variables of paracetamol, atenolol, propranolol, and benzalkonium chlorides in biota, using mussel tissue and sewage sludge. Quantum chemistry and chemometrics were also used. Results: Data on mixtures of antibiotics and surfactants in biota and the linear dynamic range of concentrations 2-80 ng.(mL)-1 and collision energy CE = 5-60 V are provided. Quantitative analysis of surfactants in biota via calibration equation ln[D″SD] = f(conc.) yields the exact parameter |r| = 0.99991, examining the peaks of BAC-C12 at m/z 212.209 ± 0.1 and 211.75 ± 0.15 for tautomers of fragmentation ions. Exact parameter |r| = 1 has been obtained, correlating the theory and experiments in determining the 3D molecular structures of ions of paracetamol at m/z 152, 158, 174, 301, and 325 in biota.

Parallel Reaction Monitoring Mode for Atenolol Quantification in Dried Plasma Spots by Liquid Chromatography Coupled with High-Resolution Mass Spectrometry

In this study, we reported a rapid, sensitive, robust, and validated method for atenolol quantification in dried plasma spots (DPS) by liquid chromatography with high-resolution mass spectrometry (LC-HRMS) using parallel reaction monitoring mode (PRM). Aliquots of 25 µL human plasma were placed onto Whatman 903 Cards and air-dried. Disks (3.2 mm internal diameter) were punched, and a 100 µL working internal standard solution was added to each sample and then incubated on a shaker for 15 min at 40 °C, followed by rapid centrifugation (10,000× g, 10 s). The supernatant was transferred into 300 µL vials for subsequent LC–HRMS analysis. After chromatographic separation, atenolol and the internal standard were quantified in positive-ion parallel reaction monitoring mode by detection of all target product ions at 10 ppm tolerances. The total time of the analysis was 5 min. The calibration curve was linear in the range of 5–1000 ng/mL with interday and intraday precision levels and biases of <14.4%, and recovery was 62.9–81.0%. The atenolol in DPS was stable for ≥30 days at 25 and 4 °C. This fully validated method is selective and suitable for atenolol quantitation in DPS using LC–HRMS.

METHODS OF METOPROLOL ANALYSIS IN DRUGS AND BIOLOGICAL FLUIDS: REVIEW AND SUGGESTIONS

Background. Analytical method is increasingly implemented into fundamental pharmaceutical chemistry and analysis, considering their high sensitivity, accuracy, specificity and expressiveness. Objective. Metoprolol’s analytical method development was the research goal. Methods. The sources were world recognized journals (1990-2019) and key words used as filter were “metoprolol”, “spectrophotometry” “high-performance liquid chromatography, HPLC”, “quantitative analysis”, “validation”. Results. Chromatographic methods of analysis have the highest specificity and objectivity and allow qualitative and quantitative determination of Active Pharmaceutic Ingredient (API) in combined dosage forms and biological fluids without prior components separation. The main disadvantage of the described API analysis methods is long terms from the beginning of chromatography to API release and specific solvents used as the mobile phase in HPLC. New methods development and selection such chromatographic conditions that provide high speed and high efficiency at lower pressure of the system are essential. Also, the reduction of analysis time is achieved by simplifying the conditions for sample preparation. Conclusions. Analysts are constantly working on developing new analysis methods and their optimization in order to save time and consumables, which also ensures the efficiency of the developed method. There is no monograph on the substance or dosage forms of metoprolol in SPhU. Therefore, some of the developed methods should be suggested for the SPhU monograph, which is important for ensuring pharmacopoeial quality control of medicines in Ukraine.

Development and Validation of a Method for the Analysis of Bisoprolol and Atenolol in Human Bone

A method based on gas chromatography-mass spectrometry (GC-MS) is described for the determination of bisoprolol and atenolol in human bone. After the addition of lobivolol as internal standard, pulverized samples were incubated in acetonitrile for 1 h under ultrasounds. After adjusting the pH of the samples to 6, they were centrifuged, and the supernatants were subjected to solid phase extraction. Elution was achieved by using 3 mL of 2% ammonium hydroxide in 80:20 dichloromethane:isopropanol solution. Eluted samples were evaporated and derivatized. Chromatography was performed on a fused silica capillary column and analytes were determined in the selected-ion-monitoring (SIM) mode. The assay was validated in the range 0.1-0.3 ng/mg (depending on the drug) to 150 ng/mg, the mean absolute recoveries were 60% for bisoprolol and 106% for atenolol, the matrix effect was 69% for bisoprolol and 70% for atenolol and process efficiency was 41% for bisoprolol and 80% for atenolol. The intra- and inter-assay accuracy values were always better than 12%. The validated method was then applied to bone samples from two real forensic cases in which toxicological analysis in blood were positive for atenolol in the first case (0.65 µg/mL) and bisoprolol in the second case (0.06 µg/mL). Atenolol was found in bone samples from the corresponding case at the approximate concentration of 148 ng/mg and bisoprolol was found at 8 ng/mg.

Air-assisted liquid-liquid microextraction using floating organic droplet solidification for simultaneous extraction and spectrophotometric determination of some drugs in biological samples through chemometrics methods

An air assisted liquid-liquid microextraction by applying the solidification of a floating organic droplet method (AALLME-SFOD) coupled with a multivariate calibration method, namely partial least squares (PLS), was introduced for the fast and easy determination of Atenolol (ATE), Propanolol (PRO) and Carvedilol (CAR) in biological samples via a spectrophotometric approach. The analytes would be extracted from neutral aqueous solution into 1-dodecanol as an organic solvent, using AALLME. In this approach a low-density solvent with a melting point close to room temperature was applied as the extraction solvent. The emulsion was immediately formed by repeatedly pulling in and pushing out the aqueous sample solution and extraction solvent mixture via a 10-mL glass syringe for ten times. After centrifugation, the extractant droplet could be simply collected from the aqueous samples by solidifying the emulsion at a lower than the melting point temperature. In the next step, analytes were back extracted simultaneously into the acidic aqueous solution. Derringer and Suich multi-response optimization were utilized for simultaneous optimizing the parameters of three analytes. This method incorporates the benefits of AALLME and dispersive liquid-liquid microextraction considering the solidification of floating organic droplets (DLLME-SFOD). Calibration graphs under optimized conditions were linear in the range of 0.30-6.00, 0.32-2.00 and 0.30-1.40μg mL^-1 for ATE, CAR and PRO, respectively. Other analytical parameters were obtained as follows: enrichment factors (EFs) were found to be 11.24, 16.55 and 14.90, and limits of detection (LODs) were determined to be 0.09, 0.10 and 0.08μg mL^-1 for ATE, CAR and PRO, respectively. The proposed method will require neither a highly toxic chlorinated solvent for extraction nor an organic dispersive solvent in the application process; hence, it is more environmentally friendly.

Simultaneous estimation of amlodipine and atenolol in human plasma: a sensitive LC–MS/MS method validation and its application to a clinical PK study

Background: A highly sensitive, specific and rapid LC–ESI-MS/MS method has been developed and validated for simultaneous quantification of amlodipine (AMD) and atenolol (ATL) in human plasma (200 µl) using AMD-d4 and ATL-d7, respectively, as an internal standard (IS) as per the regulatory guidelines. Results: The SPE method was used to extract the analytes and IS from human plasma. The chromatographic resolution of AMD, ATL and corresponding IS was achieved using an isocratic flow on a C18 column. The total chromatographic run time was 3 min. A linear response function was established for the range of concentrations 50–8000 pg/ml and 10–800 ng/ml for AMD and ATL, respectively, in human plasma. Conclusion: The intra- and inter-day accuracy and precision values for AMD and ATL met the acceptance as per regulatory guidelines. The validated assay was applied to a fixed-dose combination of AMD and ATL (Adopin-AT®) PK study in humans.

Simultaneous determination of atenolol and amiloride by capillary electrophoresis with capacitively coupled contactless conductivity detection (C4D)

Capillary electrophoresis coupled with a capacitively coupled contactless conductivity detector (CE-C(4)D) has been employed for the determination of the β-blocker drugs (atenolol and amiloride) in pharmaceutical formulations. 150 mM acetic acid was used as background electrolyte. The influence of several factors (detector excitation voltage and frequency, buffer concentration, applied voltage, capillary temperature, and injection time) was studied. Non-UV absorbing L-valine was used as an internal standard; the analytes were all separated in less than 7 min. The separation was carried out in normal polarity mode at 28 °C, 25 kV, and using hydrodynamic injection (25 s). The separation was effected in a bare fused-silica capillary 75 μm × 52 cm. The CE-C(4)D method was validated with respect to linearity, limit of detection and quantification, accuracy, precision, and selectivity. Calibration curves were linear over the range 5-250 μg mL(-1) for the studied analytes. The relative standard deviations of intra- and inter-day precisions of migration times and corrected peak areas were less than 6.0%. The method showed good precision and accuracy and was successfully applied to the simultaneous determination of the β-blocker drugs in different pharmaceutical tablets.

Simultaneous determination of metoprolol and α-hydroxymetoprolol in human plasma using excitation–emission matrix fluorescence coupled with second-order calibration methods

Background: Metoprolol (MET) is a β1-adrenoceptor antagonist, which is widely used in the treatment of cardiovascular diseases, and α-hydroxymetoprolol (α-OHM) is its hydroxylated metabolite. Owing to their similar structures, optimization of the condition for the chromatography approach, which is in common use for determination, is both time consuming and laborious. Results: A new and effective strategy that combines the excitation–emission matrix fluorescence with second-order calibration methods was developed for simultaneous determination of MET and α-OHM in human plasma. Conclusion: Although the fluorescence spectra of MET and α-OHM overlapped and a large number of unknown and uncalibrated fluorescent components coexisted, the developed method enables accurate concentrations together with reasonable resolution of excitation and emission profiles for the analytes of interest. An additional advantage of the proposed method is that there is no need for separation and sample pretreatment, in addition to lower cost than traditional methods.

Bioanalysis of drug in tissue: current status and challenges

Distribution of drugs into tissues is an important determinant of the overall PK and PD profile. Thus, bioanalysis of drugs and their metabolites in tissues can play an important role in understanding the pharmacological and toxicological properties of new drug candidates. Unlike liquid matrices, bioanalysis in tissues offers unique challenges such as proper tissue sampling, appropriate tissue sample preparation, efficient extraction of the analytes from the tissue homogenates, and demonstration of stability and recovery of analytes in intact tissues. This article provides a systematic review of tissue sample analysis for small molecules using LC–MS/MS. The authors provide rationale for tissue sample analysis, and discuss strategies for method development, method qualification or validation, and sample analysis. Unique aspects of method development and qualification/validation are highlighted based on authors’ direct experiences and literature summary. Analysis using intact tissue samples such as MALDI imaging is also briefly discussed.

Identification and characterization of stressed degradation products of metoprolol using LC/Q-TOF-ESI-MS/MS and MS(n) experiments

A rapid, specific and reliable isocratic high-performance liquid chromatography combined with quadrupole time-of-flight electrospray ionization tandem mass spectrometry (LC/Q-TOF-ESI-MS/MS) method has been developed and validated for the identification and characterization of stressed degradation products of metoprolol. Metoprolol, an anti-hypertensive drug, was subjected to hydrolysis (acidic, alkaline and neutral), oxidation, photolysis and thermal stress, as per ICH-specified conditions. The drug showed extensive degradation under oxidative and hydrolysis (acid and base) stress conditions. However, it was stable to thermal, neutral and photolysis stress conditions. A total of 14 degradation products were observed and the chromatographic separation of the drug and its degradation products was achieved on a C(18) column (4.6 × 250 mm, 5 µm). To characterize degradation products, initially the mass spectral fragmentation pathway of the drug was established with the help of MS/MS, MS(n) and accurate mass measurements. Similarly, fragmentation pattern and accurate masses of the degradation products were established by subjecting them to LC-MS/QTOF analysis. Structure elucidation of degradation products was achieved by comparing their fragmentation pattern with that of the drug. The degradation products DP(2) (m/z 153) and DP(14) (m/z 236) were matched with impurity B, listed in European Pharmacopoeia and British Pharmacopoeia, and impurity I, respectively. The LC-MS method was validated with respect to specificity, linearity, accuracy and precision.

Tandem mass spectrometric analysis of novel diquaternary ammonium gemini surfactants and their bromide adducts in electrospray-positive ion mode ionization

Gemini surfactants are cationic lipids which are utilized for both in vitro and in vivo gene delivery. Structurally, they are comprised of two hydrophobic tail regions with polar head termini that are attached to one another through a spacer region. Structural elucidation and characterization of 29 novel diquaternary ammonium gemini surfactant molecules were achieved using a quadrupole time-of-flight mass spectrometer (QqToF-MS) and a quadrupole-hexapole-quadrupole mass spectrometer (QhQ-MS). The tested compounds were categorized into four distinct structural families based upon the composition of the spacer region. Single stage (MS), tandem stage (MS/MS) and quasimulti-stage (quasi MS(3)) mass spectrometric analysis allowed for confirmation of each gemini surfactant's molecular composition and structure through the identification of common and unique product ions. Identification of similarities in the gemini surfactants' fragmentation behaviour resulted in the production of a universal fragmentation pathway that can assist in the future MS/MS analysis of novel quaternary ammonium gemini surfactants, with unique product ions being indicative of specific structural elements. Furthermore, evidence for the association of agemini surfactant with bromine counter ion was confirmed during MS analysis of tested gemini surfactants regardless of their chemical composition; previously, evidence for bromine and gemini surfactant association was only observed with compounds bearing short alkyl spacer regions. MS/MS analysis of the bromine adducts was also confirmatory to the molecular structure.Understanding the ionization and fragmentation behaviour of gemini surfactants, including bromine adducts, will allow for future qualitative and quantitative identification of these novel drug delivery agents within biological samples.

Electrically enhanced microextraction for highly selective transport of three β-blocker drugs

Facilitated transport of three β-blocker drugs including atenolol (ATE), betaxolol (BET) and propranolol (PRO) was investigated under electrical field across a supported liquid membrane (SLM) using phosphoric acid derivatives as selective ion carriers, dissolved in 2-nitro phenyl octyl ether (NPOE). In the presence of di-(2-ethylhexyl) phosphate (DEHP) and tris-(2-ethylhexyl) phosphate (TEHP) in the membrane phase, the three β-blockers showed completely different transport behaviors which enabled highly selective separation of the drugs. Each β-blocker migrated from 3 mL of sample solutions, through a thin layer of specific organic solvent immobilized in the pores of a porous hollow fiber, and into a 15 μL acidic aqueous acceptor solution present inside the lumen of the fiber. The influences of fundamental parameters affecting the transport of target drugs including type of ion carrier for selective separation of each drug and its concentration in the membrane phase, extraction voltage, time of transport, pH of donor and acceptor phases, stirring speed of donor phase and salt effect were studied and optimized. After microextraction process, the extracts were analyzed by high-performance liquid chromatography with ultraviolet detection. Under optimal conditions, ATE was selectively extracted from different saliva samples with recovery of 37%, which corresponded to preconcentration factor of 74. A good linearity was achieved for calibration curve with a coefficient of determination higher than 0.997. Limits of detection and intra-day precision (n=3) were less than 2 μg L(-1) and 8.8%, respectively.

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.

A highly sensitive LC-MS/MS method capable of simultaneously quantitating celiprolol and atenolol in human plasma for a cassette cold-microdosing study

A highly sensitive simultaneous quantitative method for a cassette cold-microdosing study on celiprolol and atenolol was developed with liquid chromatography-tandem mass spectrometry. The method utilizes a combination of solid-phase extraction (SPE) with strong cation exchange (SCX) cartridge columns and reversed-phase chromatography with an ODS analytical column. SCX-SPE cartridge columns (100 mg sorbent) were used for a selective extraction of celiprolol, atenolol and metoprolol (internal standard) from 500 μL of human plasma samples. Turbo-ion spray at positive mode was employed for the ionization of the drug compounds. Quantitation was performed on a triple quadrupole mass spectrometer by selected reaction monitoring with the transitions of m/z 380 to m/z 251 for celiprolol and m/z 267 to m/z 145 for atenolol. Separation of analytes was achieved on an ODS column (100 mm length × 2.1 mm id, 3 μm) by a gradient elution with 10 mM formic acid and methanol by varying their proportion at a flow rate of 0.2 mL/min. The method was validated in the range of 1-250 pg/mL for celiprolol and 2.5-250 pg/mL for atenolol and was successfully applied to the elucidation of pharmacokinetic profiling in a cold cassette microdosing study of the β-blockers.

Simple and rapid HPLC method for simultaneous determination of atenolol and chlorthalidone in spiked human plasma

A simple, sensitive and rapid chromatographic method was developed and validated for the simultaneous quantification of atenolol and chlorthalidone in human plasma using hydrochlorothiazide as internal standard (IS). The method utilized proteins precipitation with acetonitril as the only sample preparation involved prior to reverse phase-HPLC. The analytes were chromatographed on Shim-pack cyanopropyl column with isocratic elution with 10 mM KH2PO4 (pH 6.0) - methanol (70:30, v/v) at ambient temperature with flow rate of 1 mL min(-1) and UV detection at 225 nm. The chromatographic run time was less than 10 min for the mixture. The calibration curves were linear over the range of 0.1-10 μg mL(-1). The method was validated in terms of accuracy, precision, absolute recovery, freeze-thaw stability, bench-top stability and re-injection reproducibility. The within- and between-day accuracy and precision were found to be within acceptable limits <15%. The analytes were stable after three freeze-thaw cycles (deviation <15%). The proposed method was specific for the simultaneous determination of atenolol and chlorthalidone in human plasma where there was no interference from endogenous biological substances.

Determination of metoprolol in human plasma and urine by high-performance liquid chromatography with fluorescence detection

A simple, specific and sensitive HPLC method has been developed for the determination of metoprolol in human plasma and urine. Separation of metoprolol and atenolol (internal standard) was achieved on an Ace C(18) column (5 microm, 250 mm x 4.6 mm id) using fluorescence detection with lambda(ex)=276 nm and lambda(em)=296 nm. The mobile phase consists of methanol-water (50:50, v/v) containing 0.1% TFA. The analysis was performed in less than 10 min with a flow rate of 1 mL/min. The assay was linear over the concentration range of 3-200 and 5-300 ng/mL for plasma and urine, respectively. The LOD were 1.0 and 1.5 ng/mL for plasma and urine, respectively. The LOQ were 3.0 and 5.0 ng/mL for plasma and urine, respectively. The extraction recoveries were found to be 95.6 +/- 1.53 and 96.4 +/- 1.75% for plasma and urine, respectively. Also, the method was successfully applied to three patients with hypertension who had been given an oral tablet of 100 mg metoprolol.

Caco-2/TC7 cell line characterization for intestinal absorption: how reliable is this in vitro model for the prediction of the oral dose fraction absorbed in human?

Caco-2 cell line is one of the most used in vitro model to study intestinal absorption of compounds at screening level. Several clones have been isolated from Caco-2 cell line and characterized for their activities. Among them, TC7 clone was isolated from a late passage of the parental Caco-2 line and has shown to consist of a more homogeneous population with respect to the most representative functions of the small intestinal enterocytes, with more developed intercellular junctions. On the basis of these characteristics, it was selected within the framework of the EU A-Cute-Tox project to check its suitability to predict intestinal transport. In the present study, drugs, synthetic or natural chemicals have been characterized for their absorption profile in TC7 cells cultivated on semi-permeable filters for 21 days. The absorption experiments have been performed with the highest nontoxic concentration as determined in a preliminary set of cytotoxicity tests. The apparent permeability coefficient (P(app)) has been extrapolated by calculating the passage of the test compound from the donor to the receiver compartment as a time function. The samples have been collected at different time intervals and the concentration of the test compounds analyzed by analytical methods (HPLC, GC, GC/MS). The P(app) obtained with the TC7 clone are comparable to those obtained with the parental cell line. However, some drawbacks related to the experimental system have been highlighted (i.e. low mass balance, adsorption to the plastics), on the basis of which some compounds were excluded from the analysis. In order to check the predictability of the model, a regression analysis has been performed by plotting P(app) values vs. the fraction absorbed in humans (FA, expressed as % of the administered dose). Additional elaborations have highlighted that the specific absorption pathway (passive, active and carrier-mediated) and other factors (i.e. efflux proteins and/or metabolic activity) can strongly affect the robustness of the prediction model. On the basis of the obtained results, TC7 clone has shown to be a model for passive diffusion as reliable as the parental cell line. However, we have remarked the non-suitability of the TC7 cells to predict intestinal absorption: (i) for highly lipophilic compounds; (ii) for poorly absorbed compounds; or (iii) when transporter-mediated routes and/or first pass metabolism are involved. The preliminary study of those factors likely influencing compound biokinetics, as well as the characterization of the cellular model with respect to metabolic and transporter competence, would help in the interpretation of data.

Fibers with polypyrrole and polythiophene phases for isolation and determination of adrenolytic drugs from human plasma by SPME-HPLC

In this study, polypyrrole (PPy) and polythiophene (PTh) SPME coatings and their ability to extract selected adrenolytic drugs with different physico-chemical properties from standard solutions and human plasma samples were evaluated. In measurements metoprolol, oxprenolol, mexiletine, propranolol, and propaphenon were investigated. The main parameters such as extraction time, desorption conditions and pH influence were examined. Inter-day precisions were in range 0.1-2.0%, 1.1-2.9%, 1.3-2.6%, 0.1-2.6% and 0.3-2.1% for metoprolol, oxprenolol, mexiletine, propranolol and propaphenon, respectively. Accuracies were less than 15%, which was evaluated by analyzing preparation samples of five replicates. The method was successfully applied to human plasma samples spiked with selected adrenolytic drugs. The method was linear in the concentration range from 1 to 10microg/ml for all of studied adrenolytic drugs using human plasma samples. The PTh-SPME coating displayed higher extraction efficiency towards the target analytes in comparison to PPy-SPME. The reproducibility of the extraction using polypyrrole and polythiophene fibers was confirmed by variation coefficients lower than 8% and 3%, respectively.