Utility of synchronous fluorimetry for the concurrent quantitation of metoprolol and ivabradine

Metoprolol combined with ivabradine have been determined up to nanogram level simultaneously relied on the synchronous fluorescence spectra. First derivative amplitudes of the synchronous spectrofluorimetric spectra are recorded at Δλ = 40 nm using ethanol as diluting solvent. Metoprolol can be measured at 286 nm which is the zero-crossing point of ivabradine, and the later can be measured at 296 nm. The calibration plots were found to be linear over the ranges of concentrations: 100.0-1000.0 ng/mL and 10.0-200.0 ng/mL for metoprolol and ivabradine, respectively. Validation of the procedure was performed using the International Council of Harmonization guidelines. Values of LODs were found to be 28.89, 2.80 ng/mL and LOQs were 87.56, 8.49 ng/mL for metoprolol and ivabradine, respectively. As the two drugs are co-administered safely and effectively to reduce heart rate, angina attacks, the current methodology is utilized for the concurrent analysis of them in their single ingredient pharmaceutical preparations, synthetic mixtures, and biological fluids. The designed method, being cost-effective and simple procedure, is the first method for metoprolol and ivabradine simultaneous analysis. The results agreed statistically with the comparison methods.

Metoprolol and Its Degradation and Transformation Products Using AOPs-Assessment of Aquatic Ecotoxicity Using QSAR

Pharmaceuticals are found in waterbodies worldwide. Conventional sewage treatment plants are often not able to eliminate these micropollutants. Hence, Advanced Oxidation Processes (AOPs) have been heavily investigated. Here, metoprolol is exposed to UV irradiation, hydrogen peroxide, and ozonation. Degradation was analyzed using chemical kinetics both for initial and secondary products. Photo-induced irradiation enhanced by hydrogen peroxide addition accelerated degradation more than ozonation, leading to complete elimination. Degradation and transformation products were identified by high-performance liquid-chromatography coupled to high-resolution higher-order mass spectrometry. The proposed structures allowed to apply Quantitative Structure-Activity Relationship (QSAR) analysis to predict ecotoxicity. Degradation products were generally associated with a lower ecotoxicological hazard to the aquatic environment according to OECD QSAR toolbox and VEGA. Comparison of potential structural isomers suggested forecasts may become more reliable with larger databases in the future.

Vortex assisted liquid-liquid microextraction based on in situ formation of a natural deep eutectic solvent by microwave irradiation for the determination of beta-blockers in water samples

In this study, a simple, green, and reliable method combining vortex-assisted liquid-liquid microextraction based on in situ formation of a novel hydrophobic natural deep eutectic solvent (NADES-VA-LLME) and high-performance liquid chromatography (HPLC) was developed for the determination of metoprolol and propranolol in water samples. The novel NADES was synthesized in situ within only 20 s by subjecting the water sample containing azelaic acid and thymol to microwave irradiation at 50 ˚C. Initial studies indicated that a 17:1 ratio of thymol to azelaic acid yielded the highest response for analytes. The influence of 7 parameters, including NADES volume, salt amount, sample pH, vortex time, centrifugation time, microwave time, and temperature, were screened using a 2^7-3 fractional factorial design. The obtained significant parameters were optimized by response surface methodology employing a Box-Behnken design. The method displayed satisfactory linearity (r=0.9996) for metoprolol and propranolol with limits of detection of 0.2 and 0.1 µg/L, respectively. The relative standard deviation at 2.5, 40, and 80 µg/L levels was lower than 6%, with accuracy in the range of 90.8-100.2%. Enrichment factors were 147.0 and 144.4 for metoprolol and propranolol, respectively. This study demonstrates that the developed in situ NADES-VA-LLME-HPLC technique can be considered as a fast and environmentally friendly alternative for isolation/preconcentration of β-blockers from water samples.

Tuning down the environmental interests of organoclays for emerging pollutants: Pharmaceuticals in presence of electrolytes

The impact of electrolytes on the adsorption of emerging pollutants: pharmaceuticals onto layered materials: a raw clay mineral and its nonionic and cationic organoclay derivatives was studied. The selected pharmaceuticals: amoxicillin, norfloxacin, sulfamethoxazole, metoprolol, carbamazepine, and trimethoprim show different electric charges: zwitterionic, anionic, cationic and neutral and hydrophobic character (different LogP). Without any salts, the set of complementary data obtained by UV and infrared spectroscopies, X-ray diffraction points out the importance of the electric charge which represents a key parameter in both the spontaneity and feasibility of the adsorption. In contrast, the hydrophobicity of the analytes plays a minor role but determines the magnitude of the adsorbed amount of pharmaceuticals onto organoclays. With a dual hydrophilic and hydrophobic behavior, nonionic organoclay appears to be the most polyvalent material for the removal of the pharmaceuticals. In the presence of electrolytes (NaCl at a concentration of 1 × 10^-2 mol L^-1), both nonionic and cationic organoclays show a decrease of their efficiencies, whereas the adsorption is particularly enhanced for Na-Mt except for the cationic species (trimethoprim and metoprolol). Thus, in realistic experimental conditions close to those of natural effluents, raw clay mineral appears as the most appropriate sorbent for the studied pharmaceuticals while it raises the question of the usefulness of organoclays in water remediation strategy.

Comparative research on the metabolism of metoprolol by four CYP2D6 allelic variants in vitro with LC-MS/MS

Specific study about the effect of cytochrome P450 2D6 (CYP2D6) polymorphisms on the metabolism of clinic drugs is of great significance for drug safety investigation. Here, the interaction between CYP2D6 variants (*1, *2, *10, *39) and metoprolol (MET) was intensively researched in vitro from the aspect of drug-enzyme kinetic study. To obtain quantitative data, α-hydroxymetoprolol (main metabolite of MET) was selected as an ideal analyte and an LC-MS/MS method was adopted for sample determination. Firstly, by selecting suitable internal standard and optimizing separation condition, the LC-MS/MS method was established and validated. Then, the drug-enzyme incubation system was optimized by two parameters: incubation time and amount of enzyme. Lastly, the interaction between CYP2D6 allelic variants and MET was characterized by K_m, V_max and CL_int. As a result, four CYP2D6 enzymes displayed diverse K_m or V_max towards MET and the values of CL_int showed a wide range from 8.91 to 100%. Relative to CYP2D6*1 (CL_int*1 = 100%), CYP2D6*2 demonstrated the second high catalytic activity (CL_int*2/*1 = 74.87%) while CYP2D6*39 (CL_int*39/*1 = 29.65%) and CYP2D6*10 (CL_int*10/*1 = 8.91%) showed minimal catalytic activity. This comprehensive in vitro data suggested the prominent influence of CYP2D6 polymorphisms on the metabolism of MET, which could offer valuable information for personalized administration of MET in clinic.

Occurrence and enantiomer profiles of β-blockers in wastewater and a receiving water body and adjacent soil in Tianjin, China

A total of 58 samples were collected from hospitals, municipal wastewater treatment plants (WWTPs), a receiving water body (Dagu Drainage Canal, DDC), and adjacent farmland in Tianjin City, China, in May and November 2013 and were analyzed for five common β-blockers (atenolol, sotalol, metoprolol, propranolol, and nadolol) to elucidate their source, occurrence and fate in a typical city in China. The profiles of the enantiomers of the β-blockers in some samples were examined. Sotalol, metoprolol and propranolol were frequently detected, atenolol was less frequently detected, and nadolol was mostly not detected. Generally, the concentrations in hospital wastewaters occurred from <LOQ to 10 μg/L, while concentrations in municipal WWTP water samples ranged from <LOQ to 5.2 μg/L. Hence, both hospitals and WWTPs acted as sources of β-blockers in the environment. Sotalol, metoprolol and propranolol were determined in soils adjacent to the DDC with concentrations up to hundreds of ng/kg in the topsoil and declining levels in the subsoil. Seasonal variation was observed with samples obtained in May showing higher concentrations, both in the canal and the adjacent soil, which could be ascribed to greater consumption of these drugs, lower temperature and less precipitation in the spring and the former winter. Enantiomeric fractions (EFs) of metoprolol and propranolol in soil samples showed a trend of enrichment of E1 (first-eluted) compared to E2 (second-eluted), while sotalol was almost racemic. In the DDC, no significant difference was found for the pair enantiomers of each β-blocker, while in hospital and WWTP wastewaters, E1 predominated.

Biodegradability of fluoxetine, mefenamic acid, and metoprolol using different microbial consortiums

The biodegradation of fluoxetine, mefenamic acid, and metoprolol using ammonium-nitrite-oxidizing consortium, nitrite-oxidizing consortium, and heterotrophic biomass was evaluated in batch tests applying different retention times. The ammonium-nitrite-oxidizing consortium presented the highest biodegradation percentages for mefenamic acid and metoprolol, of 85 and 64% respectively. This consortium was also capable to biodegrade 79% of fluoxetine. The heterotrophic consortium showed the highest ability to biodegrade fluoxetine reaching 85%, and it also had a high potential for biodegrading mefenamic acid and metoprolol, of 66 and 58% respectively. The nitrite-oxidizing consortium presented the lowest biodegradation of the three pharmaceuticals, of less than 48%. The determination of the selected pharmaceuticals in the dissolved phase and in the biomass indicated that biodegradation was the major removal mechanism of the three compounds. Based on the obtained results, the biodegradation kinetics was adjusted to pseudo-first-order for the three pharmaceuticals. The values of k _biol for fluoxetine, mefenamic acid, and metoprolol determined with the three consortiums indicated that ammonium-nitrite-oxidizing and heterotrophic biomass allow a partial biodegradation of the compounds, while no substantial biodegradation can be expected using nitrite-oxidizing consortium. Metoprolol was the less biodegradable compound. The sorption of fluoxetine and mefenamic acid onto biomass had a significant contribution for their removal (6-14%). The lowest sorption coefficients were obtained for metoprolol indicating that the sorption onto biomass is poor (3-4%), and the contribution of this process to the global removal can be neglected.

Development of potential candidate reference materials for drugs in bottom sediment, cod and herring tissues

Regular use of a reference material and participation in a proficiency testing program can improve the reliability of analytical data. This paper presents the preparation of candidate reference materials for the drugs metoprolol, propranolol, carbamazepine, naproxen, and acenocoumarol in freshwater bottom sediment and cod and herring tissues. These reference materials are not available commercially. Drugs (between 7 ng/g and 32 ng/g) were added to the samples, and the spiked samples were freeze-dried, pulverized, sieved, homogenized, bottled, and sterilized by γ-irradiation to prepare the candidate materials. Procedures for extraction and liquid chromatography coupled with tandem mass spectrometry were developed to determine the drugs of interest in the studied material. Each target drug was quantified using two analytical procedures, and the results obtained from these two procedures were in good agreement with each other. Stability and homogeneity assessments were performed, and the relative uncertainties due to instability (for an expiration date of 12 months) and inhomogeneity were 10-25% and 4.0-6.8%, respectively. These procedures will be useful in the future production of reference materials.

Transformation of atenolol, metoprolol, and carbamazepine in soils: The identification, quantification, and stability of the transformation products and further implications for the environment

Pharmaceuticals are a large group of substances that have been recognized as environmental contaminants in recent years. Research on the pharmaceutical fate in soils is currently limited or missing. In this study, three pharmaceuticals (atenolol (ATE), carbamazepine (CAR), and metoprolol (MET)) were introduced to soils and exposed for 61 day under aerobic conditions. Thirteen different soils were used in the study to increase the understanding of pharmaceutical behaviour in the soil matrix. Ten metabolites were detected and tentatively identified. Some of them, such as atenolol acid (AAC), carbamazepine 10,11-epoxide (EPC), 10,11-dihydrocarbamazepine (DHC), trans-10,11-Dihydro-10,11-dihydroxy carbamazepine (RTC), and metoprolol acid (MAC), were consequently confirmed using commercial reference standards. It was concluded that the aerobic conditions of the experiment determined the pharmaceutical degradation pathway of studied compounds in the soils. The different amounts/rates and degradation of the transformation products can be attributed to differences in the soil properties. ATE degraded relatively quickly compared with CAR, whereas MET degradation in the soils was unclear. The persistence of CAR and its metabolites, in combination with low CAR sorption, enable the transportation of CAR and its metabolites within soils and into the ground water. Thus, CAR may cause adverse effects on the environment and humans.

Measured and predicted environmental concentrations of carbamazepine, diclofenac, and metoprolol in small and medium rivers in northern Germany

This study evaluated the impact of secondary municipal effluent discharge on carbamazepine, diclofenac, and metoprolol concentrations in small and medium rivers in northern Germany and compared the measured environmental concentrations (MECs) to the predicted environmental concentrations (PECs) calculated with four well-established models. During a 1-year sampling period, secondary effluent grab samples were collected at four wastewater treatment plants (WWTPs) together with grab samples from the receiving waters upstream and downstream from the wastewater discharge points. The carbamazepine, diclofenac, and metoprolol concentrations were analyzed with high-performance liquid chromatography-tandem mass spectrometry (HPLC/MS-MS) after solid phase extraction. In the secondary effluents, 84-790 ng/L carbamazepine, 395-2100 ng/L diclofenac, and 745-5000 ng/L metoprolol were detected. The carbamazepine, diclofenac, and metoprolol concentrations analyzed in the rivers downstream from the secondary effluent discharge sites ranged from <5 to 68, 370, and 520 ng/L, respectively. Most of the downstream pharmaceutical concentrations were markedly higher than the corresponding upstream concentrations. The impact of wastewater discharge on the MECs in rivers downstream from the WWTPs was clearly demonstrated, but the correlations of the MECs with dilution factors were poor. The smallest rivers exhibited the largest maximum MECs and the widest ranges of MECs downstream from the wastewater discharge point. Three of the four tested models were conservative, as they showed higher PECs than the MECs in the rivers downstream from the WWTPs. However, the most detailed model underestimated the diclofenac concentrations.

Double-wavelength overlapping resonance Rayleigh scattering technique for the simultaneous quantitative analysis of three β-adrenergic blockade

Four simple and accurate spectrophotometric methods were proposed for the simultaneous determination of three β-adrenergic blockade, e.g. atenolol, metoprolol and propranolol. The methods were based on the reaction of the three drugs with erythrosine B (EB) in a Britton-Robinson buffer solution at pH4.6. EB could combine with the drugs to form three ion-association complexes, which resulted in the resonance Rayleigh scattering (RRS) intensity that is enhanced significantly with new RRS peaks that appeared at 337 nm and 370 nm, respectively. In addition, the fluorescence intensity of EB was also quenched. The enhanced scattering intensities of the two peaks and the fluorescence quenched intensity of EB were proportional to the concentrations of the drugs, respectively. What is more, the RRS intensity overlapped with the double-wavelength of 337 nm and 370 nm (so short for DW-RRS) was also proportional to the drugs concentrations. So, a new method with highly sensitive for simultaneous determination of three bisoprolol drugs was established. Finally, the optimum reaction conditions, influencing factors and spectral enhanced mechanism were investigated. The new DW-RRS method has been applied to simultaneously detect the three β-blockers in fresh serum with satisfactory results.

Derivation of water quality standards for carbamazepine, metoprolol, and metformin and comparison with monitoring data

Environmental quality standards (EQSs) for 3 pharmaceuticals in surface water were derived: carbamazepine (epilepsy), metoprolol (heart failure), and metformin (diabetes). In recent years, these pharmaceuticals have been detected frequently in Dutch surface waters. The proposed standards are based on ecotoxicity data from national and European authorization dossiers and additional information obtained from open literature. The methods used are in accordance with the methodology of the Water Framework Directive and national frameworks for risk limit derivation. Only the exposure route regarding direct ecotoxic effects on ecosystems could be taken into account for deriving EQSs. The exposure route of secondary poisoning of fish-eating animals was not triggered, and not enough data were available or accessible to derive an EQS for the exposure of humans due to consumption of fish. Monitoring data for surface waters worldwide show that the proposed quality standards for carbamazepine may be exceeded. It could be expected that when carbamazepine use increases or effluents are diluted less during dry seasons, standards will be exceeded more often.

Impact assessment of emission management strategies of the pharmaceuticals Metformin and Metoprolol to the aquatic environment using Bayesian networks

The issue of pharmaceuticals in the environment has caused increasing concern in the recent years and various strategies have been proposed to tackle this problem. This work describes a Bayesian network (BN)-based socio-ecological impact assessment of a set of measures aimed at reducing the entry of pharmaceuticals in the aquatic environment. The measures investigated were selected across three sectors: public health market, environmental politics and drug design innovation. The BN model was developed for two drugs, Metformin and Metoprolol, and it models the distribution of the Predicted Environmental Concentration (PEC) values as a function of different measures. Results show that the sensitivity of the PEC for the two drugs to the measures investigated reflects the distinct drug characteristics, suggesting that in order to ensure the successful reduction of a broad range of substances, a spectrum of measures targeting the entire lifecycle of a pharmaceutical should be implemented. Furthermore, evaluation of two scenarios reflecting different emission management strategies highlights that the integrated implementation of a comprehensive set of measures across the three sectors results in a more extensive reduction of the contamination. Finally, the BN provides an initial forecasting tool to model the PEC of a drug as a function of a combination of measures in a context-specific manner and possible adaptations of the model are proposed.

Designing green derivatives of β-blocker Metoprolol: a tiered approach for green and sustainable pharmacy and chemistry

The presences of micro-pollutants (active pharmaceutical ingredients, APIs) are increasingly seen as a challenge of the sustainable management of water resources worldwide due to ineffective effluent treatment and other measures for their input prevention. Therefore, novel approaches are needed like designing greener pharmaceuticals, i.e. better biodegradability in the environment. This study addresses a tiered approach of implementing green and sustainable chemistry principles for theoretically designing better biodegradable and pharmacologically improved pharmaceuticals. Photodegradation process coupled with LC-MS(n) analysis and in silico tools such as quantitative structure-activity relationships (QSAR) analysis and molecular docking proved to be a very significant approach for the preliminary stages of designing chemical structures that would fit into the "benign by design" concept in the direction of green and sustainable pharmacy. Metoprolol (MTL) was used as an example, which itself is not readily biodegradable under conditions found in sewage treatment and the aquatic environment. The study provides the theoretical design of new derivatives of MTL which might have the same or improved pharmacological activity and are more degradable in the environment than MTL. However, the in silico toxicity prediction by QSAR of those photo-TPs indicated few of them might be possibly mutagenic and require further testing. This novel approach of theoretically designing 'green' pharmaceuticals can be considered as a step forward towards the green and sustainable pharmacy field. However, more knowledge and further experience have to be collected on the full scope, opportunities and limitations of this approach.

[Intentional poisoning of two wives by their husband?]

The authors report on the death of two women who were married to the same man one after the other. Exhumation and toxicological investigation of the first wife, who had died 7 years before, did not produce any conclusive evidence of homicide. With regard to the circumstances of death of the second wife the husband made different statements. According to the result of the chemical and toxicological investigations death was caused by acute intoxication with the beta-blocker metoprolol. The man was found guilty of killing on request (which is a criminal offence in Germany) by administering the beta-blocker metoprolol through a transnasal gastric tube.

Oxidation-coagulation of β-blockers by K2FeVIO4 in hospital wastewater: assessment of degradation products and biodegradability

This study investigated the degradation of atenolol, metoprolol and propranolol beta-blockers by ferrate (K2FeO4) in hospital wastewater and in aqueous solution. In the case of hospital wastewater, the effect of the independent variables pH and [Fe(VI)] was evaluated by means of response surface methodology. The results showed that Fe(VI) plays an important role in the oxidation-coagulation process, and the treatment of the hospital wastewater led to degradations above 90% for all the three β-blockers, and to reductions of aromaticity that were close to 60%. In addition, only 17% of the organic load was removed. In aqueous solution, the degradation of the β-blockers atenolol, metoprolol and propranolol was 71.7%, 24.7% and 96.5%, respectively, when a ratio of 1:10 [β-blocker]:[Fe(VI)] was used. No mineralization was achieved, which suggests that there was a conversion of the β-blockers to degradation products identified by liquid chromatography/mass spectrometry tandem. Degradation pathways were proposed, which took account of the role of Fe(VI). Furthermore, the ready biodegradability of the post-process samples was evaluated by using the closed bottle test, and showed an increase in biodegradability. The use of the ferrate advanced oxidation technology seems to be a useful means of ensuring the remediation of hospital and similar wastewater.

Influence of competing inorganic cations on the ion exchange equilibrium of the monovalent organic cation metoprolol on natural sediment

The aim of this study was to systematically investigate the influence of the mono- and divalent inorganic ions Na(+) and Ca(2+) on the sorption behavior of the monovalent organic cation metoprolol on a natural sandy sediment at pH=7. Isotherms for the beta-blocker metoprolol were obtained by sediment-water batch tests over a wide concentration range (1-100000 μg L(-1)). Concentrations of the competing inorganic ions were varied within freshwater relevant ranges. Data fitted well with the Freundlich sorption model and resulted in very similar Freundlich exponents (n=0.9), indicating slightly non-linear behavior. Results show that the influence of Ca(2+) compared to Na(+) is more pronounced. A logarithmic correlation between the Freundlich coefficient K(Fr) and the concentration or activity of the competing inorganic ions was found allowing the prediction of metoprolol sorption on the investigated sediment at different electrolyte concentrations. Additionally, the organic carbon of the sediment was completely removed for investigating the influence of organic matter on the sorption of metoprolol. The comparison between the experiments with and without organic carbon removal revealed no significant contribution of the organic carbon fraction (0.1%) to the sorption of metoprolol on the in this study investigated sediment. Results of this study will contribute to the development of predictive models for the transport of organic cations in the subsurface.

Fate of β-blockers in aquifer material under nitrate reducing conditions: batch experiments

The fate of the three environmentally relevant β-blockers atenolol, metoprolol and propranolol has been studied in batch experiments involving aquifer material and nitrate reducing conditions. Results from the about 90 d long tests indicate that abiotic processes, most likely sorption, jointly with biotransformation to atenololic acid were responsible for the 65% overall removal observed for atenolol. Zero order kinetics, typical of enzyme-limited reactions, controlled the transformation of this beta blocker to its corresponding carboxylic acid. The mass balance evidences that no mineralization of atenolol occurs in the biotic experiment and that atenololic acid is more stable than its parent compound under the studied conditions. This finding stresses the importance of considering atenololic acid as target compound in the environmental studies on the fate of atenolol. For metoprolol and propranolol the results from the experiment suggest a slower sorption to be the dominant removal process, which led to final decreases in concentrations of 25-30% and 40-45%, respectively. Overall, the removals observed in the experiments suggest that subsurface processes potentially constitute an alternative water treatment for the target beta-blockers, when compared to the removals reported for conventional wastewater treatment plants.

[Methods for the protection against counterfeit medications. Part 2. The assessment of interlot dispersion of the metoprolol succinate tablets fabricated by different manufacturers]

This paper reports the results of analysis of the metoprolol succinate tablets fabricated by two different manufacturers, Akrikhin (Russia) and AstraZeneka (Sweden) by near-IR spectroscopy in the combination with the chemometric processing of the data obtained (discriminative analysis). It is concluded that this method is applicable for the assessment of interlot dispersion of the metoprolol succinate tablets.

[The methods for the protection against counterfeit medications. Part 1. The estimation of the quality of metoprolol succinate substance and tablets from different manufacturers in terms of "identity" and "active ingredient content"]

This paper was designed to report the results of analysis of metoprolol succinate substance and tablets obtained from two manufacturers, Akrikhin (Russia) and AstraZeneca (Sweden). The analysis was performed by spectroscopy in the near IR region and followed by the chemometric treatment of the data obtained. The method was used to confirm the "identity" of metoprolol succinate tablets. The approach to distinguishing the differences between pharmaceutical dosage forms produced by different manufacturers is proposed. Also, the method for the qualitative determination of metoprolol succinate in the pharmaceutical formulations has been developed.

Photochemical fate of beta-blockers in NOM enriched waters

Beta-blockers, prescribed for the treatment of high blood pressure and for long-term use after a heart attack, have been detected in surface and ground waters. This study examines the photochemical fate of three beta-blockers, atenolol, metoprolol, and nadolol. Hydrolysis accounted for minor losses of these beta-blockers in the pH range 4-10. The rate of direct photolysis at pH 7 in a solar simulator varied from 6.1 to 8.9h(-1) at pH 7. However, the addition of a natural organic matter (NOM) isolate enhanced the photochemical loss of all three compounds. Indirect photochemical fate, generally described by reactions with hydroxyl radical (OH) and singlet oxygen ((1)ΔO(2)), and, the direct reaction with the triplet excited state, (3)NOM(⁎), also varied but collectively appeared to be the major loss factor. Bimolecular reaction rate constants of the three beta-blockers with (1)ΔO(2) and OH were measured and accounted for 0.02-0.04% and 7.2-38.9% of their loss, respectively. These data suggest that the (3)NOM(⁎) contributed 50.6-85.4%. Experiments with various (3)NOM(⁎) quenchers supported the hypothesis that it was singly the most important reaction. Atenolol was chosen for more detailed investigation, with the photoproducts identified by LC-MS analysis. The results suggested that electron-transfer could be an important mechanism in photochemical fate of beta-blockers in the presence of NOM.

Application of a novel solid-phase-extraction sampler and ultra-performance liquid chromatography quadrupole-time-of-flight mass spectrometry for determination of pharmaceutical residues in surface sea water

In the present study, a multi-residue method based on a bag-solid phase extraction (bag-SPE) technique was evaluated for determination of 10 pharmaceuticals in surface water close to the effluent of a sewage treatment plant (STP) and along a coastal gradient from a STP effluent. The 10 compounds selected were caffeine, atenolol, metoprolol, oxazepam, carbamazepine, ketoprofen, naproxen, ibuprofen, diclofenac and gemfibrozil. All analyses were performed using ultra-performance liquid chromatography (UPLC) combined with quadrupole time-of-flight (QTOF) mass spectrometry. The detection limits (LOD) ranged from 1.0 to 13 ng L(-1). The method showed linear concentration ranges from 25 to 800 ng L(-1) with regression coefficients (R(2)) better than 0.9801. The recoveries of the selected analytes ranged from 11 to 65% with relative standard deviations (RSD) of <16% and inter-day variations of less than 18%. Isotopically labeled surrogate standards were used to compensate for sampling losses and matrix effects. Four of the selected 10 pharmaceuticals (caffeine, metoprolol, oxazepam and carbamazepine) were quantified, at concentrations ranging from 4 to 210 ng L(-1).

Optimization and establishment of a validated stability-indicating HPLC method for study of the stress degradation behavior of metoprolol succinate

A stability-indicating HPLC method has been established for analysis of metoprolol succinate in the presence of products generated in a stress degradation study. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis, and thermal decomposition. Extensive degradation was found to occur in an alkaline medium and under thermal stress. Minimum degradation was observed in an acidic medium and under photolytic and oxidative stress. Successful separation of the drug from its degradation products formed under stress conditions was achieved on a C18 column using sodium dihydrogen phosphate buffer-acetonitrile (70 + 30) mobile phase. The flow rate was 1 mL/min, and the detection wavelength was 274 nm. The method was validated for linearity, range, precision, accuracy, LOQ, and LOD. Because the method effectively separates the drugs from their degradation products, it can be used as a stability-indicating method.

Stability studies of expired tablets of metoprolol tartrate and propranolol hydrochloride. Part 1. Content determination

In recent years the growing interest in drug stability problem has been observed. The stability of pharmaceutical products seems to play an important role from the economical point of view. However, there are not many studies that reported about the stability of drugs past their expiration dates. The objective of the current study was to determine tablet content of expired tablets and tablets with expiry date has not been exceeded. The analyzed tablets contained metoprolol tartrate (50 mg) and propranolol hydrochloride (10 mg), respectively. Content determination was performed using HPLC method with UV detection. The proposed method was validated with regard to linearity, sensitivity, intermediate accuracy and precision. No discrepancies between the results of determination and the declared values range for all the analyzed tablets were observed. The results of performed study might suggest that storage of analyzed batches of tablets over time period exceeding the expiry date given by the manufacturer did not influence their contents.

Simultaneous quantification of tiloronoxim and tilorone in human urine by liquid chromatography-tandem mass spectrometry

A simple, sensitive and specific HPLC method with tandem mass spectrometry (HPLC/MS/MS) detection has been developed and validated for the simultaneous quantification of tiloronoxim and its major active metabolite, tilorone, in human urine. The analytes, together with metoprolol, which was employed as an internal standard (IS), were extracted with a mixture solvent of chloroform/ethyl ether (1/2, v/v). The chromatographic separation was performed on a narrow-bore reversed phase HPLC column with a gradient mobile phase of methanol/water containing 15 mM ammonium bicarbonate (pH 10.5). The API 3,000 mass spectrometer was equipped with a TurboIonSpray interface and was operated on positive-ion, multiple reaction-monitoring (MRM) mode. The mass transitions monitored were m/z 426.3-->100.0, m/z 411.3-->100.0 and m/z 268.3-->116.1 for tiloronoxim, tilorone and the IS, respectively. The assay exhibited a linear dynamic range of 1-100 ng/ml for both tiloronoxim and tilorone based on the analysis of 0.2 ml aliquots of urine. The lower limit of quantification was 1 ng/ml for both compounds. Acceptable precision and accuracies were obtained for concentrations over the standard curve ranges. Run time of 8 min for each injection made it possible to analyze a high throughput of urine samples. The assay has been successfully used to analyze human urine samples from healthy volunteers.

Spectrophotometric and column high-performance liquid chromatographic methods for simultaneous estimation of metoprolol tartrate and hydrochlorothiazide in tablets

Simple, accurate, economical, and reproducible UV spectrophotometric and column high-performance liquid chromatographic (HPLC) methods were developed for simultaneous estimation of a 2-component drug mixture of metoprolol tartrate and hydrochlorothiazide in combined tablet dosage form. The first method used the simultaneous equation method with 7 mixed standards and the absorption maxima at 223 and 271 nm, respectively, for metoprolol tartrate and hydrochlorothiazide in methanol. Linearity was observed in the concentration ranges of 4-24 and 2-16 microg/mL for metoprolol tartrate and hydrochlorothiazide, respectively. The developed HPLC method used a reversed-phase C18 column and methanol-water (95 + 5) mobile phase at an ambient temperature of 27 +/- 2 degrees C and UV detection at 225 nm; the run time was 10 min, and quantification was based on peak area. The injection repeatability and intraday and interday repeatability were calculated. Paracetamol was used as an internal standard for the HPLC method, and linearity was observed in the concentration range of 5-50 microg/mL for metoprolol and 2-20 microg/mL for hydrochlorothiazide. The proposed methods were successfully applied for the determination of metoprolol tartrate and hydrochlorothiazide in bulk powder and dosage form. The results obtained were analyzed statistically, and there was no significant difference between the 2 methods. The validation was performed according to International Conference on Harmonization guidelines.

Elimination of beta-blockers in sewage treatment plants

beta-Blockers are used to treat high blood pressure as well as patients recovering from heart attacks. In several studies, they were detected in surface water, thus indicating incomplete degradability of these substances in sewage treatment plants (STPs). In this study, we determined the sorption coefficients (K(D)) and degradation rates of the four beta-blockers sotalol, atenolol, metoprolol and propranolol in sludge from an STP operating with municipal wastewater. The sorption coefficients (K(D), standard deviations in brackets) were determined as 0.04(+/-0.035), 0.04(+/-0.033), 0.00(+/-0.023) and 0.32(+/-0.058) Lg(-1)(COD), and the pseudo-first-order degradation rate constants were estimated to be 0.29(+/-0.02), 0.69(+/-0.05), 0.58(+/-0.05) and 0.39(+/-0.07) Ld(-1)g(-1)(COD) for sotalol, atenolol, metoprolol and propranolol, respectively. These values translate into a typical elimination in STPs (sludge concentrations of 4g(COD)L(-1) and a hydraulic retention time of 6h) of 25%, 37%, 44% and 50% for sotalol, propranolol, metoprolol and atenolol, respectively. These results are also confirmed by measurements in two municipal STPs for atenolol, sotalol and propranolol. The estimated eliminations are slightly too high for metoprolol.

Kinetics and degradation products for direct photolysis of beta-blockers in water

Related to improving persistence assessment of active pharmaceutical ingredients (APIs), direct aqueous photolysis of beta-blockers: propranolol (hydrochloride salt), atenolol, and metoprolol (succinate salt) were investigated by exposing the samples (0.0003-10 mg L(-1)) to a solar irradiator (filtered xenon lamp: 290-800 nm) at 20-26 degrees C. Results suggested that direct photolysis in optically dilute solutions followed pseudo first-order kinetics. The measured half-lives of propranolol, atenolol, and metoprolol were approximately 16, 350, and 630 h, respectively. These were 3-5 orders of magnitude slower than the estimated minimum half-lives. The measured half-lives were related to day light surface conditions by comparing the light intensity of the lamp and the sun at different latitudes and seasons. Major direct photolysis products were identified from propranolol that led to a proposed reaction pathway, involving ring oxidation, rearrangement, and deoxygenation. Electron paramagnetic resonance (EPR) spectroscopy results confirmed that at least one carbon-based radical intermediate was formed during the direct photolysis of propranolol in aqueous solutions. The overall results demonstrated that with fast direct photolysis half-lives, propranolol is unlikely to be persistent in natural waters. Further work is needed to investigate indirect photolysis of atenolol and metoprolol in surface waters in order to understand the overall persistence of these APIs in the environment.

Determination of Atenolol and Metoprolol by Capillary Electrophoresis with Tris(2,2'-bipyridyl)ruthenium(II) Electrochemiluminescence Detection

Capillary electrophoresis (CE) coupling with a tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL) detection technique was developed for the analysis of two beta-blockers, atenolol (AT) and metoprolol (ME). The parameters that influence the separation and detection, including the buffer pH and concentration, the separation voltage, the detection potential and Ru(bpy)(3)(2+) concentration, were optimized in detail. The calibration curve was linear over a concentration range of two or three orders of magnitude for the two beta-blockers. The detection limits for AT and ME were 0.075 and 0.005 microM (S/N = 3). The relative standard deviations (n = 8) of the ECL intensity and the migration time were 2.65 and 0.22% for AT, 2.82 and 0.34% for ME, respectively. The proposed method was applied to determine AT and ME in spiked urine samples; satisfactory results were obtained.

Ion-pair supercritical fluid chromatography of metoprolol and related amino alcohols on diol silica

In this paper, a chromatographic system based on carbon dioxide with methanol as mobile phase, and diol silica as stationary phase has been investigated for metoprolol and related amino alcohols by addition of strong acids to systems with triethylamine base as primary additive. Standard conditions used were 10% of methanol, containing 24 mM of acid and 18 mM of triethylamine, in carbon dioxide with a flow rate of 1.5 ml min(-1). The column dimensions were 125 mm x 4 mm I.D. and kept at 40 degrees C with a back pressure of 150 bar. Effects on selectivity were stronger with trifluoroacetic acid than with ethanesulfonic acid. From a large set of related analytes, it was shown that selectivity changes were significant when the structure close to the nitrogen of the amino alcohol analyte differed. The stability of the column in the short time perspective was examined and it showed negligible changes. For a diastereoisomeric pair, not resolved in a basic system with triethylamine nor by addition of ethanesulfonic acid, resolution improved to about 2.1 with trifluoroacetic acid. The described approach offers a way to tune the selectivity of SFC systems when amines are analyzed without the need to change stationary phase for the chromatographic separation.

Stereoisomer quantification of the -blocker drugs atenolol, metoprolol, and propranolol in wastewaters by chiral high-performance liquid chromatography–tandem mass spectrometry

A chiral liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) method was developed and validated for measuring individual enantiomers of three beta-blocker drugs (atenolol, metoprolol, and propranolol) in wastewater treatment plant (WWTP) influents and effluents. Mean recoveries of the pharmaceuticals ranged from 67 to 106%, and the limits of detection of the analytes were 2-17 ng/L in wastewater effluents. The method was demonstrated by measuring, for the first time, the stereoisomer composition of target analytes in raw and treated wastewaters of two Canadian WWTPs. In these trials, racemic amounts of the three drugs were observed in influent of one wastewater treatment plant, but nonracemic amounts were observed in another. Effluents of the two plants contained nonracemic amounts of the drugs. These results indicate that biologically-mediated stereoselective processes that differ among WWTPs had occurred to eliminate individual enantiomers of the target analytes.

Determination of metoprolol tartrate in tablets and human urine using flow-injection chemiluminescence method

In this paper, a simple, rapid and sensitive flow-injection chemiluminescence method has been developed for the determination of metoprolol tartrate, which acts as a kind of sensitizer in the chemiluminescence emission from the redox of SO(3)(2-) with Ce(IV) in acidic medium. Under the optimized conditions, the proposed method allows the measurement of metoprolol tartrate over the range of 1.5 x 10(-8) to 7.3 x 10(-6)mol/L with a detection limit of 4.7 x 10(-9)mol/L (3sigma), and the relative standard deviation for 7.3 x 10(-7)mol/L metoprolol tartrate (n=11) is 2.20%. The utility of this method was demonstrated by determining metoprolol tartrate in tablets and human urine sample.

High-performance liquid chromatography method development and validation for simultaneous determination of five model compounds, antipyrine, metoprolol, ketoprofen, furosemide and phenol red, as a tool for the standardization of rat in situ intestinal permeability studies using timed wavelength detection

A simple, precise, accurate and rugged reversed-phase high-performance liquid chromatography (HPLC) method has been developed and validated for the simultaneous determination of five permeability model compounds, viz. antipyrine, metoprolol, ketoprofen, furosemide and phenol red. The method was intended to standardize rat in situ single-pass intestinal perfusion studies to assess the intestinal permeability of drugs in the market as well as new chemical entities. Optimum resolution was achieved by gradient elution on a Symmetry Shield C-18 analytical column with the mobile phase consisting of a mixture of aqueous potassium dihydrogen orthophosphate (pH 5.5; 0.01 m) and methanol at a flow rate of 1.5 mL/min. The retention times of antipyrine, metoprolol, ketoprofen, phenol red and furosemide were about 9, 12, 13, 16 and 17 min, respectively. Data acquisition was carried out using a photo diode array detector in the wavelength range 210-600 nm. Extraction of chromatograms was carried out by timed wavelength. Data obtained in all studies indicated that the method was suitable for the intended purpose. The validated method was found to be linear and precise in the working range. Suitability of storage under various conditions and freeze/thaw impact at cold temperature were established to ensure complete sample recovery without any stability issues. Recovery very close to the spiked amounts indicated that the method was highly accurate and suitable for use on routine basis.

Determination of metoprolol and hydrochlorothiazide by derivative spectrophotometric method in pharmaceutical preparations

A procedure for simultaneous determination of metoprolol and hydrochlorothiazide in tablets by employing derivative spectrophotometry, "zero-crossing" method was developed. The third order derivative absorption spectra at lambda approximately 281 nm were used for metoprolol and the first order derivative spectra at lambda approximately 282 nm were used for hydrochlorothiazide. No interferences were found between both determined constituents and those of matrix. A good accuracy and precision of simultaneous determination of metoprolol and hydrochlorothiazide were confirmed by statistical analysis. The recovery of individual constituents under established conditions is very high and ranges from 98.79% to 99.39%. Linearity is maintained within a wide concentration range from 100.0 microg mL(-1) to 300.0 microg mL(-1) and from 12.5 microg mL(-1) to 37.5 microg mL(-1) for metoprolol and hydrochlorothiazide, respectively. The detection limit is 5.0 microg mL(-1) for metoprolol and 1.5 microg mL(-1) for hydrochlorothiazide. The corresponding quantitation limits are 15.0 microg mL(-1) for metoprolol and 4.5 microg mL(-1) for hydrochlorothiazide.

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

Hypertension is a growing medical concern in the United States. With the number of Americans suffering from hypertension increasing, the use of antihypertensives such as beta-blockers is increasing as well. In fact, three beta-blockers - atenolol, metoprolol and propranolol - were among the 200 most prescribed medications in the United States in 2003. Pilots that successfully manage their hypertension can remain certified to fly. The Federal Aviation Administration currently designates approximately 8% of active pilots as "hypertensive with medication". The Civil Aerospace Medical Institute (CAMI) performs toxicological evaluation on victims of fatal aviation accidents. At CAMI beta-blockers are analyzed using gas chromatography with mass spectrometric detection. We have, however, recently developed a liquid chromatography with mass spectrometric detection (LC/MS) method for the simultaneous quantitation of three commonly prescribed beta-blockers, atenolol, metoprolol and propranolol. One advantage of our LC/MS method is the specificity provided by an ion trap MS. Utilizing an ion trap MS, we were able to conduct MS/MS and MS/MS/MS on each analyte. This method also eliminates the time-consuming and costly derivitization step necessary during GC/MS analysis. Additionally, by utilizing this novel method, any concerns about beta-blocker metabolite and/or sample matrix interference are eliminated. The limits of detection for this method ranged from 0.39 to 0.78 ng/mL and the linear dynamic range was generally 1.6-3200 ng/mL. The extraction efficiencies for each analyte ranged from 58% to 82%. This method was successfully applied to postmortem fluid and tissue specimens obtained from victims of three separate aviation accidents.

Post-mortem redistribution of three beta-blockers in the rabbit

To consider the role of the physico-chemical properties of drugs in their post-mortem redistribution, we designed the present study to investigate the influence of lipophilicity using an experimental rabbit model. Three beta-blockers (BB), atenolol, metoprolol and propranolol, with a similar dissociation constant (pK (a)) and increasing partition coefficient (K (p)) were administered intravenously to 18 rabbits. One hour after the last administration, the animals were killed by thiopental injection and placed in a supine position at room temperature. Autopsies were performed at 0, 2, 6, 12, 24 and 48 h post-mortem. Concentrations of the three BB were determined in fluids (right and left cardiac blood, peripheral blood, urine, bile, stomach content, vitreous humour) and tissues (cardiac muscle, lungs, liver, brain, diaphragm, iliopsoas muscle) using a previously published, validated liquid chromatography-electrospray-mass spectrometry method. Our results show that lipophilicity influences post-mortem redistribution of the molecules in a certain number of anatomical sites such as the stomach, lungs, cardiac muscle, cardiac blood or liver, but does not appear to intervene in other sites such as the brain or the vitreous humour.

Analysis of small molecules by ultra thin-layer chromatography-atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry

The feasibility of ultra thin-layer chromatography atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry (UTLC-AP-MALDI-MS) has been studied in the analysis of small molecules. Because of a thinner adsorbent layer, the monolithic UTLC plates provide 10-100 times better sensitivity in MALDI analysis than conventional high performance thin-layer chromatography (HPTLC) plates. The limits of detection down to a low picomole range are demonstrated by UTLC-AP-MALDI-MS. Other advantages of UTLC over HPTLC include faster separations and lower solvent consumption. The performances of AP-MALDI-MS and vacuum MALDI-MS have been compared in the analysis of small drug molecules directly from the UTLC plates. The desorption from the irregular surface of UTLC plates with an external AP-MALDI ion source combined with an ion trap instrument provides clearly less variation in measurements of m/z values when compared with a vacuum MALDI-time-of-flight (TOF) instrument. The performance of the UTLC-AP-MALDI-MS method has been applied successfully to the purity analysis of synthesis products produced by solid-phase parallel synthesis method.

On-line cation-exchange preconcentration and capillary electrophoresis coupled by tee joint interface

An on-line preconcentration method based on ion exchange solid phase extraction was developed for the determination of cationic analytes in capillary electrophoresis (CE). The preconcentration-separation system consisted of a preconcentration capillary bonded with carboxyl cation-exchange stationary phase, a separation capillary for zone electrophoresis and a tee joint interface of the capillaries. Two capillaries were connected closely inside a 0.3 mm i.d. polytetrafluoroethylene tube with a side opening and fixed together by the interface. The preparations of the preconcentration capillaries and interface were described in detail in this paper. The on-line preconcentration and separation procedure of the analysis system included washing and conditioning the capillaries, loading analytes, filling with buffer solution, eluting analytes and separating by capillary zone electrophoresis (CZE). Several analysis parameters, including sample loading flow rate and time, eluting solution and volume, inner diameter and length of preconcentration capillary etc., were investigated. The proposed method enhanced the detection sensitivity of CE-UV about 5000 times for propranolol and metoprolol compared with normally electrokinetic injection. The detection limits of propranolol and metoprolol were 0.02 and 0.1 microg/L with the proposed method respectively, whereas those were 0.1 and 0.5 mg/L with conventional electrokinetic injection. The experiment results demonstrate that the proposed technique can increase the preconcentration factor evidently.

[Study of large-volume electrokinetic injection of capillary zone electrophoresis by using transient isotachophoresis]

A sample pre-concentration method that combined field-amplified sample injection (FASI) induced by acetonitrile with transient isotachophoresis was applied to achieve effective concentration and the separation of cations in high-salt samples. Several important factors are discussed, such as buffer systems, terminating ions, column effective length and injection time of sample and terminating solution. A capillary column of 50 microm i. d. x 65 cm (effective length of 50 cm) was employed. Solutions of 400 mmol/L LiAc-HAc (pH 4.5) and 400 mmol/L beta-alanine-HAc (pH 4.5) were used as buffer solution and terminating electrolyte, respectively. The injection times of sample solution and terminating electrolyte were 270 and 90 s, respectively. Compared with conventional electrokinetic injection, the sensitivity of the proposed method was improved about 280-fold. The detection limits of propranolol and metoprolol achieved 2 x 10(-3) and 8 x 10(-3) mg/L, respectively.

Validated Kinetic Spectrophotometric Method for the Determination of Metoprolol Tartrate in Pharmaceutical Formulations

A kinetic spectrophotometric method has been described for the determination of metoprolol tartrate in pharmaceutical formulations. The method is based on reaction of the drug with alkaline potassium permanganate at 25+/-1 degrees C. The reaction is followed spectrophotometrically by measuring the change in absorbance at 610 nm as a function of time. The initial rate and fixed time (at 15.0 min) methods are utilized for constructing the calibration graphs to determine the concentration of the drug. Both the calibration graphs are linear in the concentration range of 1.46 x 10(-6)-8.76 x 10(-6) M (10.0-60.0 microg per 10 ml). The calibration data resulted in the linear regression equations of log (rate)=3.634+0.999 log C and A=6.300 x 10(-4)+6.491 x 10(-2) C for initial-rate and fixed time methods, respectively. The limits of quantitation for initial rate and fixed time methods are 0.04 and 0.10 microg ml(-1), respectively. The activation parameters such as E(a), DeltaH(double dagger), DeltaS(double dagger) and DeltaG(double dagger) are also evaluated for the reaction and found to be 90.73 kJ mol(-1), 88.20 kJ mol(-1), 84.54 J K(-1) mol(-1) and 63.01 kJ mol(-1), respectively. The results are validated statistically and through recovery studies. The method has been successfully applied to the determination of metoprolol tartrate in pharmaceutical formulations. Statistical comparison of the results with the reference method shows excellent agreement and indicates no significant difference in accuracy and precision.

Determination of Three β-Blockers in Biofluids and Solid Tissues by Liquid Chromatography-Electrospray-Mass Spectrometry

A LC-MS method using clenbuterol as internal standard was developed and validated for three b-blockers (BB) (atenolol, metoprolol, and propranolol) in rabbit postmortem matrices: heart, lung, kidney, liver, brain, blood, vitreous humor, gastric liquid, and urine. The BB were extracted from 2.0 mL of biofluids or 200 mg of solid tissues (after grinding and homogenization) by liquid-liquid extraction using Extrelut columns. Chromatographic separation involved a Nucleosil C18 (150 mm x 1-mm i.d., 5 microm) column together with a gradient of acetonitrile in 2mM, pH 3 ammonium formate. The compounds were ionized in the ionspray source of the atmospheric pressure mass spectrometer and fragmented by in-source collisions. The fragment ions were detected in the positive selected ion monitoring mode, targeting one quantitation and two confirmation ions per compound. The extraction recovery ranged between 10 and 40%, depending on the matrices. The limits of quantitation were 50 ng/g in tissues, 50 microg/L in blood and urine, and 10 microg/L in vitreous humor. Indeed, as preliminary results in one rabbit administered 5 mg/kg of each BB showed that BBs were more concentrated in some postmortem organs, validation was performed in the relevant concentration area in these particular tissues. The technique was found to be linear between 50 ng/g and 5000 ng/g for heart and liver, between 50 microg/L and 5000 microg/L for urine extracts, between 1000 ng/g and 50 000 ng/g for lung and kidney, and between 500 microg/L and 5000 microg/L for gastric content. A quadratic equation best fitted the calibration curve in blood between 50 microg/L and 5000 microg/L, as well as in brain between 50 ng/g and 40,000 ng/g. The correlation coefficients were all higher than 0.997. Intra- and interassay precision and accuracy fulfilled the international requirements. This simple and sensitive assay was applied to the determination of three BB in the biofluids and tissues of a rabbit as part of a preliminary step of a postmortem redistribution study and is also suitable for the routine determination of BB in forensic investigations.

NMR spectroscopic characterization of metoprolol/cyclodextrin complexes in aqueous solution: Cavity size dependency

The inclusion complex formation of a water-soluble beta(1)-selective adrenoreceptor antagonist Metoprolol (Met) with alpha-cyclodextrin (alpha-CyD), beta-cyclodextrin (beta-CyD), gamma-cyclodextrin (gamma-CyD), and 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) in aqueous solution was studied by ultraviolet (UV), circular dichroism (CD), and nuclear magnetic resonance (NMR) spectroscopies and the modes of interaction were assessed. Continuous variation plots revealed that Met forms the inclusion complexes with alpha-CyD, beta-CyD, and HP-beta-CyD in a stoichiometry of 1:1, whereas gamma-CyD forms the 2:1 complex where two Met molecules are included in one gamma-CyD cavity. NMR spectroscopic studies, including ROESY and GROESY techniques, clearly indicated that alpha-CyD with the small cavity includes the methoxyethylbenzene moiety of Met molecule shallowly in the cavity, depositing the benzene and the methoxy moieties around the secondary and primary sides, respectively, of the cavity. In the case of the beta-CyD complex, the methoxyethylbenzene moiety is more deeply included in the cavity, and it is feasible that Met may be able to enter from both primary and secondary hydroxyl sides of the cavity, forming the 1:1 complex. On the other hand, two Met molecules are included probably in an antiparallel orientation in the large gamma-CyD cavity, and the benzene moieties of Met are in contact with each other.

Polymeric matrix membrane sensors for sensitive potentiometric determination of some beta-blockers in pharmaceutical preparations

Five poly(vinyl chloride) matrix membrane sensors responsive to some beta-blockers (atenolol, bisoprolol, metoprolol, propranolol and timolol) are described and characterized. The sensors are based on the use of the ion-association complexes of the beta-blocker cations with tungstophosphate anion as electroactive materials. The performance characteristics of these sensors, evaluated according to IUPAC recommendations, reveal fast, stable and near-Nernstian response for 10(-2)-2 x 10(-7) mol l(-1) of different beta-blockers over the pH range 2-9. Many inorganic and organic cations as well as drug excipients and diluents normally used in drug formulations do not interfere. The sensors are used for direct potentiometry of beta-blockers in some pharmaceutical preparations. Validation of the method according to the quality assurance standards shows suitability of the proposed sensors for use in the quality control assessment of these drugs. Results with an average recovery of 99.1% and a mean standard deviation of +/- 1.3% of the nominal are obtained which compare fairly well with data obtained using the British Pharmacopoeia method.

Determination of beta-adrenergic receptor blocking pharmaceuticals in United States wastewater effluent

Beta adrenergic receptor antagonists (beta-Blockers) are frequently prescribed medications in the United States and have been identified in European municipal wastewater effluent, however no studies to date have investigated these compounds in United States wastewater effluent. Municipal wastewater effluent was collected from treatment facilities in Mississippi, Texas, and New York to investigate the occurrence of metoprolol, nadolol, and propranolol. Propranolol was identified in all wastewater samples analyzed (n = 34) at concentrations < or = 1.9 microg/l. Metoprolol and nadolol were identified in > or = 71% of the samples with concentrations of metoprolol < or = 1.2 microg/l and nadolol < or = 0.36 microg/l. Time course studies at both Mississippi plants and the Texas plant indicate that concentrations of propranolol, metoprolol, and nadolol remain relatively constant at each sampling period. This study indicates that beta-Blockers are present in United States wastewater effluent in the ng/l to microg/l range.

Enantiomeric separations of amino alcohols by packed-column SFC on Hypercarb with L-(+)-tartaric acid as chiral selector

The use of L-(+)-tartaric acid as a chiral mobile phase additive (CMPA) has been investigated in a packed-column SFC system. The CMPA, carbon dioxide, and methanol, containing a high concentration of aliphatic amine additive, were used as the mobile phase and Hypercarb as support [Gyllenhaal O., Karlsson A., SFC of metoprolol and other amino alcohols on Hypercarb (in preparation)]. Good enantioselectivities were obtained for tertiary amine homologues of 2-amino alcohols, used as beta-adrenoreceptor-blocking drugs. Moderate selectivities were observed for aromatic compounds having a second substituent in the ortho-position. The overall retention was influenced by the aromaticity of the analytes as well as the presence of free electron pairs in the molecule. Increased concentrations of CMPA gave higher retention and also increased the enantioselectivity. The practical utility of this present enantioselective system was demonstrated on one batch of (S)-metoprolol that was N-methylated with methyl iodide. The enantiomeric separation was accomplished within 10 min.

Enantioselective stabilization of inclusion complexes of metoprolol in carboxymethylated beta-cyclodextrin

The inclusion complexes of metoprolol (MT) and carboxymethyl-beta-cyclodextrin (CMCD) were prepared and the stability constants of the complexes were determined. Binding studies performed using high performance liquid chromatography (HPLC), UV spectrometry and capillary electrophoresis (CE) indicated that a complex with 1:1 stoichiometry is predominant in the solution. The enantiomers of MT possess relatively high affinity towards CMCD with stability constants of 288 and 262 per M for (R)- and (S)-MT, respectively. Through nuclear magnetic resonance (NMR) analysis, MT was predicted to be a bent structure with phenyl ring of MT inserted in the shielding cavity of CMCD during complex formation. The NMR data suggested that the chiral side chain and the methoxyethyl moiety of MT are aligned in the deshielding zone, above and below the CMCD torus ring.

Liquid chromatography/tandem mass spectrometric bioanalysis using normal-phase columns with aqueous/organic mobile phases - a novel approach of eliminating evaporation and reconstitution steps in 96-well SPE

Bioanalytical methods using automated 96-well solid-phase extraction (SPE) and liquid chromatography with electrospray tandem mass spectrometry (LC/MS/MS) are widely used in the pharmaceutical industry. SPE methods typically require manual steps of drying of the eluates and reconstituting of the analytes with a suitable injection solvent possessing elution strength weaker than the mobile phase. In this study, we demonstrated a novel approach of eliminating these two steps in 96-well SPE by using normal-phase LC/MS/MS methods with low aqueous/high organic mobile phases, which consisted of 70-95% organic solvent, 5-30% water, and small amount of volatile acid or buffer. While the commonly used SPE elution solvents (i.e. acetonitrile and methanol) have stronger elution strength than a mobile phase on reversed-phase chromatography, they are weaker elution solvents than a mobile phase for normal-phase LC/MS/MS and therefore can be injected directly. Analytical methods for a range of polar pharmaceutical compounds, namely, omeprazole, metoprolol, fexofenadine, pseudoephedrine as well as rifampin and its metabolite 25-desacetyl-rifampin, in biological fluids, were developed and optimized based on the foregoing principles. As a result of the time saving, a batch of 96 samples could be processed in one hour. These bioanalytical LC/MS/MS methods were validated according to "Guidance for Industry - Bioanalytical Method Validation" recommended by the Food and Drug Administration (FDA) of the United States.

Development and validation of a chiral liquid chromatographic method for the determination of atenolol and metoprolol enantiomers in tablet preparations

Atenolol (AT) and metoprolol (MT) are predominantly used in the treatment of angina pectoris, certain arrhythmias, systemic hypertension, and several other cardiovascular disorders. Both compounds are produced commercially in the racemic form, although the S-form is responsible for the desired biological effect. This paper describes a simple, rapid, precise, and accurate method for separating the enantiomers of AT and MT. AT isomers are separated by using a Chiralcel OD column (250 x 4.6 mm, 10 microm), hexane-ethanoldiethylamine-acetic acid (60 + 40 + 0.2 + 0.2, v/v/v/v) as the mobile phase, and a flow rate of 1.0 mL/min. MT isomers are separated by using a mobile phase with the same components in the following proportions (40 + 60 + 0.2 + 0.2, v/v/v/v) and a flow rate of 0.8 mL/min. Ultraviolet detection was at 276 nm for both analytes. The coefficients of variation (CVs) and average recoveries (ARs) for the R-enantiomers in samples A, B, C, D, and E were 1.15 and 101.06%, 0.74 and 99.25%, 1.05 and 102.57%, 0.84 and 101.57%, and 0.86 and 98.62%, respectively. The CVs and ARs for the S-enantiomers in samples A, B, C, D, and E were 1.33 and 98.87%, 0.99 and 100.76%, 1.17 and 101.69%, 1.26 and 100.39%, and 1.40 and 99.39%, respectively. The standard curves of R-AT, S-AT, R-MT, and S-MT showed good linearity over the concentration range studied with correlation coefficients of 0.9991, 0.998, 0.9988, and 0.999, respectively.

AAS and spectrophotometric determination of propranolol HCl and metoprolol tartrate

Two simple and accurate spectrophotometric methods are described for the determination of propranolol hydrochloride (I) and metoprolol tartrate (II). The methods are based on the reaction of each drug as a secondary amine: (a) with carbon disulphide, the formed complex extracted into iso-butyl methyl ketone (IBMK) after chelation with Cu(II) ions at pH 7.5, followed by measuring the absorbance at 435.4 nm or indirectly for the drug by flame atomic absorption spectrophotometry (AAS). The calibration graph is linear up to 40 and 60 microg ml(-1) with apparent molar absorptivities of 6.89 x 10(3) and 1.08 x 104 l mol(-1) cm(-1) and correlation coefficients of 0.9994 and 0.9995 for propranolol and metoprolol, respectively; (b) with pi-acceptors, tetracyanoethylene (TCNE), or chloranilic acid (CLA) to give highly coloured complex species. The coloured products are quantitated spectrophotometrically at 415 or 510 nm for the two drugs with TCNE and CLA, respectively, and obey Beer's Law with RSD less than 2.0. The methods were applied to the determination of these drugs in pharmaceutical preparation without interferences.