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.

Photodegradation of selected β-blockers in aqueous fulvic acid solutions: kinetics, mechanism, and product analysis

The photodegradation of the widely used β-blockers atenolol and metoprolol were investigated in the presence of fulvic acid (FA) under simulated sunlight. Both atenolol and metoprolol undergo indirect photodegradation in the FA solutions. The triplet excited state of FA ((3)FA(∗)) was verified to be main reactive species responsible for the photosensitized degradation of β-blockers. An electron transfer mechanism for the interaction between β-blockers and (3)FA(∗) was proposed on the basis of a series of experiments. Magnetic property of metal ions exhibited significant impact on photosensitized degradation. Diamagnetic metal ions such as Mg(2+), Ca(2+), Zn(2+), and Al(3+) negligibly affected the degradation. In contrast, paramagnetic metal ions including Mn(2+), Cu(2+), Fe(3+), and Cr(3+) markedly inhibited the reactions in the order of Cr(3+) < Fe(3+) < Cu(2+) < Mn(2+). The inhibition was related to the complexation ability with FA. By LC-ESI-MS/MS analysis, deisopropyl-atenolol (metoprolol) was identified as the main photosensitized product. The degradation pathways of β-blockers involving electron transfer processes were proposed. This finding strongly suggests that (3)FA(∗) was important reactive species for the degradation of β-blockers in natural waters.

Simultaneous detection of residues of 25 β₂-agonists and 23 β-blockers in animal foods by high-performance liquid chromatography coupled with linear ion trap mass spectrometry

A sensitive method has been developed for the simultaneous determination of residues of 25 β₂-agonists and 23 β-blockers in animal foods by high-performance liquid chromatography coupled with linear ion trap mass spectrometry (HPLC-LIT-MS). This method is based on a new procedure of hydrolysis and extraction by 5% trichloracetic acid, and then cleaned up by mixed strong cation exchange (MCX) cartridges coupled with a novelty cleanup step by methanol. Methanol and 0.1% formic acid were used as mobile phases for gradient elution, while a Supelco Ascentis Express Rp-Amide column was used for LC separation. ESI positive ion scan mode was used with consecutive reaction monitoring (CRM, MS³). Nine β₂-agonists labeled by the deuterium isotope were used as internal standards for quantification. The linear ranges of 48 analytes were from 5 to 200 μg/L; the coefficient of correlation was not less than 0.995. Blank pork muscle, blank liver, and blank kidney were selected as representative matrix for spiked standard recovery test. The recoveries of each compound were in the range of 46.6-118.9%, and the relative standard deviations were in the range of 1.9-28.2%. Decision limits (CCα, α = 0.01) of 48 analytes in muscles, liver, and kidney samples ranged from 0.05 to 0.49 μg/kg, and the detection capability (CCβ, β = 0.05) ranged from 0.13 to 1.64 μg/kg. This method was successfully applied to 110 real animal origin food samples including meat, liver, and kidney of pig and chicken samples.

Evaluating the polar organic chemical integrative sampler for the monitoring of beta-blockers and hormones in wastewater treatment plant effluents and receiving surface waters

Wastewater treatment plants (WWTP) are known to be a source of surface water contamination by organic compounds such as pharmaceuticals. The objective of the present work was to study the suitability of the polar organic chemical integrative sampler (POCIS) to monitor beta-blockers and hormones in effluents and surface waters. Four sampling campaigns were carried out in French rivers (the Saône, the Ardières, the Bourbre, and the Seine) between November 2007 and September 2008. Passive samplers were exposed in surface waters, upstream and downstream of WWTP outflows, and in effluents. Exposures lasted for up to 24 d to study the uptake kinetics directly in situ, and repeatability was assessed by exposure of triplicates. A good agreement was found between POCIS and water samples. With the exception of atenolol, beta-blockers showed a linear uptake during at least three weeks, and their sampling rates could be determined in situ. These sampling rates were then used to calculate time-weighted average concentrations of beta-blockers in the Seine River with an overall good accuracy and repeatability. Such calculations could not be performed for hormones because of their variable occurrences and low concentrations in water and POCIS. Polar organic chemical integrative sampler therefore seems to be a suitable tool for monitoring beta-blockers in surface waters impacted by WWTP effluents. Longer exposure durations would be necessary to determine the suitability of POCIS for monitoring hormones. Finally, preliminary assays on the use of several deuterated compounds as performance reference compounds showed promising results for deuterated atenolol.

Photocatalytic degradation of metoprolol tartrate in suspensions of two TiO2-based photocatalysts with different surface area. Identification of intermediates and proposal of degradation pathways

This study investigates the efficiency of the photocatalytic degradation of metoprolol tartrate (MET), a widely used β(1)-blocker, in TiO(2) suspensions of Wackherr's "Oxyde de titane standard" and Degussa P25. The study encompasses transformation kinetics and efficiency, identification of intermediates and reaction pathways. In the investigated range of initial concentrations (0.01-0.1 mM), the photocatalytic degradation of MET in the first stage of the reaction followed approximately a pseudo-first order kinetics. The TiO(2) Wackherr induced a significantly faster MET degradation compared to TiO(2) Degussa P25 when relatively high substrate concentrations were used. By examining the effect of ethanol as a scavenger of hydroxyl radicals (OH), it was shown that the reaction with OH played the main role in the photocatalytic degradation of MET. After 240 min of irradiation the reaction intermediates were almost completely mineralized to CO(2) and H(2)O, while the nitrogen was predominantly present as NH(4)(+). Reaction intermediates were studied in detail and a number of them were identified using LC-MS/MS (ESI+), which allowed the proposal of a tentative pathway for the photocatalytic transformation of MET as a function of the TiO(2) specimen.

In silico screening for agonists and blockers of the β(2) adrenergic receptor: implications of inactive and activated state structures

Ten crystal structures of the β(2) adrenergic receptor have been published, reflecting different signaling states. Here, through controlled-docking experiments, we examined the implications of using inactive or activated structures on the in silico screening for agonists and blockers of the receptor. Specifically, we targeted the crystal structures solved in complex with carazolol (2RH1), the neutral antagonist alprenalol, the irreversible agonist FAUC50 (3PDS), and the full agonist BI-167017 (3P0G). Our results indicate that activated structures favor agonists over blockers, whereas inactive structures favor blockers over agonists. This tendency is more marked for activated than for inactive structures. Additionally, agonists tend to receive more favorable docking scores when docked at activated rather than inactive structures, while blockers do the opposite. Hence, the difference between the docking scores attained with an activated and an inactive structure is an excellent means for the classification of ligands into agonists and blockers as we determined through receiver operating characteristic curves and linear discriminant analysis. With respect to virtual screening, all structures prioritized well agonists and blockers over nonbinders. However, inactive structures worked better for blockers and activated structures worked better for agonists, respectively. Notably, the combination of individual docking experiments through receptor ensemble docking resulted in an excellent performance in the retrieval of both agonists and blockers. Finally, we demonstrated that the induced-fit docking of agonists is a viable way of modifying an inactive crystal structure and bias it toward the in silico recognition of agonists rather than blockers.

Brain mitochondrial drug delivery: influence of drug physicochemical properties

PURPOSE

To determine the influence of drug physicochemical properties on brain mitochondrial delivery of 20 drugs at physiological pH.

METHODS

The delivery of 8 cationic drugs (beta-blockers), 6 neutral drugs (corticosteroids), and 6 anionic drugs (non-steroidal anti-inflammatory drugs, NSAIDs) to isolated rat brain mitochondria was determined with and without membrane depolarization. Multiple linear regression was used to determine whether lipophilicity (Log D), charge, polarizability, polar surface area (PSA), and molecular weight influence mitochondrial delivery.

RESULTS

The Log D for beta-blockers, corticosteroids, and NSAIDs was in the range of -1.41 to 1.37, 0.72 to 2.97, and -0.98 to 2, respectively. The % mitochondrial uptake increased exponentially with an increase in Log D for each class of drugs, with the uptake at a given lipophilicity obeying the rank order cationic>anionic>neutral. Valinomycin reduced membrane potential and the delivery of positively charged propranolol and betaxolol. The best equation for the combined data set was Log % Uptake = 0.333 Log D + 0.157 Charge - 0.887 Log PSA + 2.032 (R(2) = 0.738).

CONCLUSIONS

Drug lipopohilicity, charge, and polar surface area and membrane potential influence mitochondrial drug delivery, with the uptake of positively charged, lipophilic molecules being the most efficient.

Advances in the enantioseparation of β-blocker drugs by capillary electromigration techniques

β-Blocker drugs or β-adrenergic blocking agents are an important class of drugs, prescribed with great frequency. They are used for various diseases, particularly for the treatment of cardiac arrhythmias, cardioprotection after myocardial infarction (heart attack), and hypertension. Almost all β-blocker drugs possess one or more stereogenic centers; however; only some of them are administered as single enantiomers. Since both enantiomers can differ in their pharmacological and toxicological properties, enantioselective analytical methods are required not only for pharmacodynamic and pharmacokinetic studies but also for quality control of pharmaceutical preparations with the determination of enantiomeric purity. In addition to the chromatographic tools, in recent years, capillary electromigration techniques (CE, CEC, and MEKC) have been widely used for enantioselective purposes employing a variety of chiral selectors, e.g. CDs, polysaccharides, macrocyclic antibiotics, proteins, chiral ion-paring agents, etc. The high separation efficiency, rapid analysi,s and low consumption of reagents of electromigration methods make them a very attractive alternative to the conventional chromatographic methods. In this review, the development and applications of electrodriven methods for the enantioseparation of β-blocker drugs are reported. The papers concerning this topic, published from January 2000 until December 2010, are summarised here. Particular attention is given to the coupling of chiral CE and CEC methods to MS, as this detector provides high sensitivity and selectivity.

Degradation of pharmaceutical beta-blockers by electrochemical advanced oxidation processes using a flow plant with a solar compound parabolic collector

The degradation of the beta-blockers atenolol, metoprolol tartrate and propranolol hydrochloride was studied by electro-Fenton (EF) and solar photoelectro-Fenton (SPEF). Solutions of 10 L of 100 mg L⁻¹ of total organic carbon of each drug in 0.1 M Na₂SO₄ with 0.5 mM Fe²⁺ of pH 3.0 were treated in a recirculation flow plant with an electrochemical reactor coupled with a solar compound parabolic collector. Single Pt/carbon felt (CF) and boron-doped diamond (BDD)/air-diffusion electrode (ADE) cells and combined Pt/ADE-Pt/CF and BDD/ADE-Pt/CF cells were used. SPEF treatments were more potent with the latter cell, yielding 95-97% mineralization with 100% of maximum current efficiency and energy consumptions of about 0.250 kWh g TOC⁻¹. However, the Pt/ADE-Pt/CF cell gave much lower energy consumptions of about 0.080 kWh g TOC⁻¹ with slightly lower mineralization of 88-93%, then being more useful for its possible application at industrial level. The EF method led to a poorer mineralization and was more potent using the combined cells by the additional production of hydroxyl radicals (•OH) from Fenton's reaction from the fast Fe²⁺ regeneration at the CF cathode. Organics were also more rapidly destroyed at BDD than at Pt anode. The decay kinetics of beta-blockers always followed a pseudo first-order reaction, although in SPEF, it was accelerated by the additional production of •OH from the action of UV light of solar irradiation. Aromatic intermediates were also destroyed by hydroxyl radicals. Ultimate carboxylic acids like oxalic and oxamic remained in the treated solutions by EF, but their Fe(III) complexes were photolyzed by solar irradiation in SPEF, thus explaining its higher oxidation power. NO₃⁻ was the predominant inorganic ion lost in EF, whereas the SPEF process favored the production of NH₄⁺ ion and volatile N-derivatives.

Asthma treatment through the beta receptor: lessons from animal models

Asthma is a significant health problem worldwide with a prevalence that continues to rise and for which there is no cure. Animal models have been used for decades to investigate the cause and cures of asthma, and while they do not always mimic many of the facets of this syndrome, mechanistic animal studies are still nevertheless very useful. Animal studies with beta-agonists suggest much broader and perhaps more important roles for beta-agonists since beta-agonists reduce aspects of inflammation and may affect structural remodeling. Studies using enantiomers of beta-agonists provide a confusing picture of the degree and mechanism of the deleterious effects of racemic mixtures and/or the S-enantiomer or other classes of beta-agonists. Neural mechanisms are implicated. The future holds a promise of even more insight into the mechanisms of the acute and chronic role of the beta-adrenoceptor, asthma therapeutics, in particular, beta-agonists that will lead to a better understanding of the pathogenesis and treatment of asthma.

Design of a drug delivery system with bimodal pH dependent release of a poorly soluble drug

A delivery system which provides bimodal pH dependent release of poorly water soluble carvedilol in gastric and intestinal environment was designed. Preparation of solid dispersion with porous silica ensured a significantly higher dissolution rate of carvedilol in acidic and alkaline media in comparison to pure drug, while granulation of that solid dispersion with enteric polymer dispersion resulted in diminished immediate release in acidic media and fast release of the remaining drug in alkaline media. The ratio in quantities of first vs. second release was controlled with amount of enteric polymer dispersion used for granulation process. Desired 25 mg release of carvedilol at pH values 1.2 and 6.8 was achieved when 1.80 g of polymer per 1.0 g of solid dispersion (drug to silica ratio= 0.25 g : 2.0 g) was used.

1H and 13C NMR characteristics of β-blockers

The β-blockers are important drugs and decades of clinical experience proved their high medical status. However, to the best of our knowledge, there is no complete assignment of (1)H and (13)C NMR resonances of popular representatives: acebutolol, alpenolol, pindolol, timolol and propranolol and the published NMR data on carvedilol and atenolol are incorrect. Therefore, (1)H and (13)C NMR spectroscopy was applied for the characterization of a series of β-adrenolytics: carvedilol (1), pindolol (2), alprenolol (3), acebutolol (4), atenolol (5), propranolol (6) and timolol (7). Two-dimensional NMR experiments (COSY, HMQC, HMBC, NOESY) allowed the unequivocal assignment of (1)H and (13)C spectra for solution (DMSO-d(6) ). Salts and bases can be easily distinguished based on (13)C chemical shifts which are within 65.0-65.5 ppm (OC2) and 46.9-47.0 (NC3) for hydrochlorides and larger, ca. 68.4 ppm (OC2) and 50.3-52.6 (NC3) for bases. NMR data of 1-7 should be included in pharmacopoeias.

Electrochemical degradation of the β-blocker metoprolol by Ti/Ru 0.7 Ir 0.3 O 2 and Ti/SnO 2-Sb electrodes

Electrochemical oxidation has been proposed for the elimination of pesticides, pharmaceuticals and other organic micropollutants from complex waste streams. However, the detrimental effect of halide ion mediators and the generation of halogenated by-products in this process have largely been neglected thus far. In this study, we investigated the electrochemical oxidation pathways of the β-blocker metoprolol in reverse osmosis concentrate (ROC) from a water reclamation plant using titanium anodes coated with Ru(0.7)Ir(0.3)O(2) or SnO(2)-Sb metal oxide layers. The results of liquid chromatography-mass spectrometry analysis indicated that irrespective of the electrode coating the same oxidant species participated in electrochemical transformation of metoprolol in ROC. Although Ti/SnO(2)-Sb exhibited higher oxidizing power for the same applied specific electrical charge, the generation of large fractions of chloro-, chloro-bromo- and bromo derivatives was observed for both electrode coatings. However, degradation rates of metoprolol and its degradation products were generally higher for the Ti/SnO(2)-Sb anode. Chemical analyses of metoprolol and its by-products were complemented with bioanalytical tools in order to investigate their toxicity relative to the parent compound. Results of the bioluminescence inhibition test with Vibrio fischeri and the combined algae test with Pseudokirchneriella subcapitata indicated a substantial increase in non-specific toxicity of the reaction mixture due to the formed halogenated by-products, while the specific toxicity (inhibition of photosynthesis) remained unchanged.

Electro-Fenton and photoelectro-Fenton degradations of the drug beta-blocker propranolol using a Pt anode: identification and evolution of oxidation products

The beta-blocker propranolol hydrochloride has been degraded by electrochemical advanced oxidation processes like electro-Fenton (EF) and photoelectro-Fenton (PEF) using a single cell with a Pt anode and an air diffusion cathode (ADE) for H(2)O(2) electrogeneration and a combined system containing the above Pt/ADE pair coupled in parallel to a Pt/carbon-felt (CF) cell. Organics are mainly oxidized with hydroxyl radical (OH) formed from Fenton's reaction between added Fe(2+) and electrogenerated H(2)O(2). The PEF treatment in Pt/ADE-Pt/CF system yields almost total mineralization because OH production is enhanced by Fe(2+) regeneration from Fe(3+) reduction at the CF cathode and Fe(III) complexes with generated carboxylic acids are rapidly photodecarboxylated under UVA irradiation. Lower mineralization degree is found for PEF in Pt/ADE cell due to the little influence of UVA light on Fe(2+) regeneration. The homologous EF processes are much less potent as a result of the persistence of Fe(III)-carboxylate complexes. Aromatic intermediates such as 1-naphthol, 1,4-naphthoquinone and phthalic acid and generated carboxylic acids such as pyruvic, glycolic, malonic, maleic, oxamic, oxalic and formic are identified. While chloride ion remains stable, NH(4)(+) and NO(3)(-) ions are released to the medium. A reaction sequence for propranolol hydrochloride mineralization is proposed.

Metabolomic profiling of cellular responses to carvedilol enantiomers in vascular smooth muscle cells

Carvedilol is a non-selective β-blocker indicated in the treatment of hypertension and heart failure. Although the differential pharmacological effects of individual Carvedilol enantiomer is supported by preceding studies, the cellular response to each enantiomer is not well understood. Here we report the use of GC-MS metabolomic profiling to study the effects of Carvedilol enantiomers on vascular smooth muscle cells (A7r5) and to shed new light on molecular events underlying Carvedilol treatment. The metabolic analysis revealed alternations in the levels of 8 intracellular metabolites and 5 secreted metabolites in A7r5 cells incubated separately with S- and R-Carvedilol. Principal component analysis of the metabolite data demonstrated the characteristic metabolic signatures in S- and R-Carvedilol-treated cells. A panel of metabolites, including L-serine, L-threonine, 5-oxoproline, myristic acid, palmitic acid and inositol are closely correlated to the vascular smooth muscle contraction. Our findings reveal the differentiating metabolites for A7r5 cells incubated with individual enantiomer of Carvedilol, which opens new perspectives to employ metabolic profiling platform to study chiral drug-cell interactions and aid their incorporation into future improvement of β-blocker therapy.

FoldGPCR: structure prediction protocol for the transmembrane domain of G protein-coupled receptors from class A

Building reliable structural models of G protein-coupled receptors (GPCRs) is a difficult task because of the paucity of suitable templates, low sequence identity, and the wide variety of ligand specificities within the superfamily. Template-based modeling is known to be the most successful method for protein structure prediction. However, refinement of homology models within 1-3 A C alpha RMSD of the native structure remains a major challenge. Here, we address this problem by developing a novel protocol (foldGPCR) for modeling the transmembrane (TM) region of GPCRs in complex with a ligand, aimed to accurately model the structural divergence between the template and target in the TM helices. The protocol is based on predicted conserved inter-residue contacts between the template and target, and exploits an all-atom implicit membrane force field. The placement of the ligand in the binding pocket is guided by biochemical data. The foldGPCR protocol is implemented by a stepwise hierarchical approach, in which the TM helical bundle and the ligand are assembled by simulated annealing trials in the first step, and the receptor-ligand complex is refined with replica exchange sampling in the second step. The protocol is applied to model the human beta(2)-adrenergic receptor (beta(2)AR) bound to carazolol, using contacts derived from the template structure of bovine rhodopsin. Comparison with the X-ray crystal structure of the beta(2)AR shows that our protocol is particularly successful in accurately capturing helix backbone irregularities and helix-helix packing interactions that distinguish rhodopsin from beta(2)AR.

The structure of betaxolol studied by infrared spectroscopy and natural bond orbital theory

Betaxolol is a selective beta(1) receptor blocker used in the treatment of hypertension and glaucoma. A study of the betaxolol structure based on infrared spectroscopy and natural bond orbital (NBO) theory is the main aim of the present research. FTIR spectra of the solid betaxolol were recorded in the region from 4000 to 400cm(-1), in the temperature range between 25 and -170 degrees C. For spectral interpretation, spectrum of the deuterated betaxolol and the theoretical vibrational spectra of the conformer present in the solid obtained at the B3LYP/6-31G* level of theory, were used. Further insight into the structure was provided by natural bond orbital theory. NBO analysis of the conformer, before and after optimization, was carried out at the same level of theory referred above. Vibrational modes involved in hydrogen bond in the stretching and bending region were used in the estimation of the enthalpy using empirical correlations between enthalpy and the frequency shift that occurs as a result of the establishment of intermolecular hydrogen bonds. A detailed study of the structure of betaxolol and of its intermolecular interactions was obtained from the combination spectroscopy and NBO theory.

UV-C radiation based methods for aqueous metoprolol elimination

The endocrine disruptor metoprolol has been oxidised in aqueous solution by means of the systems UV-C, UV-C/H(2)O(2), UV-C/percarbonate, UV-C/monopersulfate, UV-C/TiO(2), UV-C/H(2)O(2)/TiO(2) and photo-Fenton. From simple photolysis experiments the quantum yield of metoprolol has been calculated (roughly 5x10(-3) mol Einstein(-1) at circumneutral pH). Addition of free radicals promoters significantly enhanced the metoprolol depletion rate. Mineralization degree was negligible when no promoter was added, while low values were achieved in the presence of either inorganic peroxides or titanium dioxide. The combination of radiation, hydrogen peroxide and TiO(2) increased the mineralization level up to values in the proximity of 45-50% under the best conditions investigated. The photo-Fenton process was the best system in terms of total oxidation (mineralization degree 70%) when optimum conditions were applied.

Photocatalytic degradation kinetics and mechanism of environmental pharmaceuticals in aqueous suspension of TiO2: a case of beta-blockers

This study investigated the photocatalytic degradation of three beta-blockers in TiO(2) suspensions. The disappearance of the compounds followed pseudo-first-order kinetics according to the Langmuir-Hinshelwood model and the rate constants were 0.075, 0.072 and 0.182 min(-1) for atenolol, metoprolol and propranolol, respectively. After 240 min irradiation, the reaction intermediates were completely mineralized to CO(2) and the nitrogen was predominantly as NH(4)(+). The influence of initial pH and beta-blocker concentration on the kinetics was also studied. From adsorption studies it appears that the photocatalytic degradation occurred mainly on the surface of TiO(2). Further studies indicated that surface reaction with OH radical was principally responsible for the degradation of these three beta-blockers. The major degradation intermediates were identified by HPLC/MS analysis. Cleavage of the side chain and the addition of the hydroxyl group to the parent compounds were found to be the two main degradation pathways for all three beta-blockers.

Environmental risk assessment of human pharmaceuticals in the European Union: A case study with the β-blocker atenolol

β-Adrenergic receptor blockers (β-blockers) are applied to treat high blood pressure, ischemic heart disease, and heart rhythm disturbances. Due to their widespread use and limited human metabolism, β-blockers are widely detected in sewage effluents and surface waters. β-Adrenergic receptors have been characterized in fish and other aquatic animals, so it can be expected that physiological processes regulated by these receptors in wild animals may be affected by the presence of β-blockers. Because ecotoxicological data on β-blockers are scarce, it was decided to choose the β-blocker atenolol as a case study pharmaceutical within the project ERAPharm. A starting point for the assessment of potential environmental risks was the European guideline on the environmental risk assessment of medicinal products for human use. In Phase I of the risk assessment, the initial predicted environmental concentration (PEC) of atenolol in surface water (500 ng L−1) exceeded the action limit of 10 ng L−1. Thus, a Phase II risk assessment was conducted showing acceptable risks for surface water, for groundwater, and for aquatic microorganisms. Furthermore, atenolol showed a low potential for bioaccumulation as indicated by its low lipophilicity (log KOW = 0.16), a low potential for exposure of the terrestrial compartment via sludge (log KOC = 2.17), and a low affinity for sorption to the sediment. Thus, the risk assessment according to Phase II-Tier A did not reveal any unacceptable risk for atenolol. Beyond the requirements of the guideline, additional data on effects and fate were generated within ERAPharm. A 2-generation reproduction test with the waterflea Daphnia magna resulted in the most sensitive no-observed-effect concentration (NOEC) of 1.8 mg L−1. However, even with this NOEC, a risk quotient of 0.003 was calculated, which is still well below the risk threshold limit of 1. Additional studies confirm the outcome of the environmental risk assessment according to EMEA/CHMP (2006). However, atenolol should not be considered as representative for other β-blockers, such as metoprolol, oxprenolol, and propranolol, some of which show significantly different physicochemical characteristics and varying toxicological profiles in mammalian studies.

Seasonal variations in the occurrence and fate of basic and neutral pharmaceuticals in a Swedish river-lake system

The seasonal variations in the occurrence of carbamazepine, atenolol, metoprolol, sotalol, and acebutolol were studied at seven sites along River Fyris from December 2007 to December 2008. Samples were collected from the effluent of a waste water treatment plant (WWTP), at one upstream site, and five downstream sites of the WWTP. During one occasion in May 2008, water samples were collected at different locations and depths in the recipient lake. All analytes except of acebutolol were present in both the river and the lake at quantifiable amounts at all sampling occasions. Carbamazepine was found in similar concentrations (about 90 ng L(-1)) at all sampling sites and all studied depths (0.5-40 m) in the lake, indicating high environmental persistence of this compound. A clear seasonal pattern was observed for the natural attenuation of the beta-blockers in the river, with the highest attenuation occurring in summer and the lowest in winter. The loss of beta-blockers on a distance of 1320 m reached up to 75% during summer time but was insignificant during winter. The seasonal variations in the loss followed the seasonal variations in water temperature and chlorophyll a mass flow suggesting that biotransformation and adsorption are the main processes responsible for the loss of the studied pharmaceuticals in River Fyris downstream the WWTP.

Effect of radiation sterilization on alprenolol in the solid state studied by high-performance thin-layer chromatography

The possibility of radiation sterilization of alprenolol (AL) has been studied. Irradiation of AL in solid form with a 25 kGy beam of electrons caused only an insignificant change in color that became more intense with increasing irradiation dose. Moreover, with increasing dose a decrease in pH, the content of water, and the degree of crystallinity were observed. AL in solid form was radiated with a high-energy electron beam (9.96 MeV) at doses from 25-400 kGy and analyzed by HPTLC using the mobile phase methanol-ammonia 25% (99 + 1, v/v). Densitometric analysis was carried out directly from chromatograms at 270 nm. The applied method was validated and characterized by good precision (RSD = 3.95%); good accuracy (80% level 100.15%, 100% level 99.99%, and 120% level 104.44%); and low LOD (LOD = 0.52 microg/zone and LOQ = 1.55 microg/zone). Chromatograms recorded for samples irradiated at the doses of 25 kGy were unchanged, but at higher doses (100-400 kGy) additional peaks corresponding to the radiodegradation products appeared (Rf = 0.24 and Rf = 0.40). The decrease in the concentration of AL was proportional to the applied radiation dose, and for 400 kGy the concentration of AL was 90.23%. The calculated radiolytic yield of the radiodegradation process was G(-AL) = 7.12 x 10(-7) mol/J.

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.

Fate of beta-blocker human pharmaceuticals in surface water: comparison of measured and simulated concentrations in the Glatt Valley Watershed, Switzerland

This study focused on the occurrence and fate of four beta-blockers (atenolol, sotalol, metoprolol, propranolol) in wastewater and surface water. Measured concentrations were compared with predicted concentrations using an implementation of the geo-referenced model GREAT-ER for the Glatt Valley Watershed (Switzerland). Particularly, the question was addressed how measured and simulated data could complement each other for the exposure assessment of human pharmaceuticals and other micropollutants entering surface water through wastewater treatment plants (WWTP). Concentrations in the Glatt River ranged from <LOQ to 83 ng L(-1) with the highest concentrations found for atenolol. Higher loads were measured on days with combined sewer overflow events during high flow conditions. GREAT-ER was able to predict spatially resolved river concentrations based on average consumption and excretion data, removal in wastewater treatment plants (WWTPs) and dissipation and degradation processes in surface water within a factor of 2. These results indicate that modelling might be sufficient to estimate daily average exposure concentrations for compounds that are either recalcitrant or whose degradation and sorption behaviour can be predicted with confidence based on laboratory experiments. Chemical measurements, in contrast, should be reserved for assessing point sources, investigating mechanisms which lead to short-term temporal fluctuations in compound loads, and determining in-situ degradation rates in conjunction with modelling.