The fate of sotalol in aqueous chlorination: Kinetics, mechanisms and ecotoxicity assessment.

Unmetabolized pharmaceuticals often enter the water treatment plants and exposed to various treatment processes. Among these water treatment processes, disinfection is a process which involves the application of chemical oxidation to remove pathogen. Untreated pharmaceuticals from primary and secondary treatment have the potential to be exposed to the chemical oxidation process during disinfection. This study investigated the kinetics and mechanism of the degradation of sotalol during chlorination process. Chlorination with hypochlorous acid (HOCl) as main reactive oxidant has been known as one of the most commonly used disinfection methods. The second order rate constant for the reaction between sotalol and free available chlorine (FAC) was found to decrease from 60.1 to 39.1M-1min-1 when the pH was increased from 6 to 8. This result was mainly attributed by the decreased of HOCl concentration with increasing pH. In the real water samples, the presence of the higher amount of organic content was found to reduce the efficiency of chlorination in the removal of sotalol. This result showed that sotalol competes with natural organic matter to react with HOCl during chlorination. After 24h of FAC exposure, sotalol was found to produce three stable transformation by-products. These by-products are mainly chlorinated compounds. According to the acute and chronic toxicity calculated using ECOSAR computer program, the transformation by-products are more harmful than sotalol.

DETERMINATION OF SOTALOL, OXPRENOLOL AND LABETALOL IN BINARY MIXTURES AND IN SPIKED HUMAN SERUM BY DERIVATIVE SPECTROPHOTOMETRIC METHOD.

The usefulness of derivative spectrophotometry for the determination of labetalol, sotalol and oxprenolol in binary mixtures and in human spiked serum was checked. To this aim a spectrophotometric analysis of samples in the UV range was carried out and the obtained results revealed that derivative spectropho- tometry allows for the fast, accurate and precise determination of the tested substances in spite of their clear interference in the zero-order spectra. For quantitative determinations "zero-crossing" technique was used to establish wavelengths for zeros of specified component. In a mixture of labetalol and oxprenolol the following wavelengths were established: D1 λ = 245.32 nm and 266.03 nm, D2 λ = 243.30 nm and 301.09 nm. respectively. D3 derivative did not show zeros suitable for quantitative analysis. For the analysis of labetalol and sotalol mixture, D3 derivative spectrophotometry was used at the following wavelengths: = 246.03 nm and λ = 249.91 rum, respectively. In this case, the curves of Dl and D2 derivatives showed no zeros that can be used in quantitative analysis. To determine the concentration of the components in a mixture containing oxprenolol and sotalol the following wavelengths were selected: for oxprenolol DI λ = 245.32 nm, D2 λ = 240.18 run, D3 λ = 232.05 nm and for sotalol Dl λ = 230.56 nm, D2 Xλ= 232.65 nm and D3 X = 238.84 tm, respectively. The developed spectrophotometric method was characterized by high sensitivity and accuracy, LOD determined for sotalol was in the range of 0.21-1.88 µg/mL, for labetalol 1.00-3.43 µg/mL and for oxprenolol 0.16-2.06 µg/mL; LOQ determined for sotalol was in the range of 0.65-5.70 µg/mL, for labetalol 3.11-10.39 µg/mL and for oxprenolol 0.47-6.23 µg/mL, depending on the composition of the tested mixture and the order of the deriv- ative. The recovery of the individual components was within the range of 100 ± 5%. The linearity range was wide and estimated for sotalol in the range of 11.00-38.50 µg/mL, for labetalol 12.80-44.80 µg/mL and for oxprenolol 12.60-44.10 µg/mL with correlation coefficients in the range of 0.9977-0.9999.

A comprehensive study of the enantioseparation of chiral drugs by cyclodextrin using capillary electrophoresis combined with theoretical approaches.

Four chiral drugs were enantioseparated by native beta-cyclodextrin (ß-CD) and negatively charged carboxymethyl-beta-cyclodextrin (CM-ß-CD) using capillary electrophoresis coupled with electrochemiluminescence detection (CE-ECL). Using 50 mM pH 5.5 Tris-H3PO4 with 10 mM CM-ß-CD as a running buffer, high resolution efficiency could be obtained. With the help of isothermal titration calorimetry (ITC), nuclear magnetic resonance (NMR) and molecular modeling, the chiral recognition mechanism was comprehensively investigated. Thermodynamic parameters data from ITC revealed that CM-ß-CD exhibited stronger binding affinity with analytes than ß-CD, and that the driving forces of CM-ß-CD responsible for chiral recognition were mainly electrostatic interactions between negatively charged CM-ß-CD and positively charged analytes. In addition, from both a macroscopic and microscopic point of view, the results of NMR and molecular modeling investigation adequately confirm the conclusion by comparing the stereochemical structures of complexes. Combination of ITC, NMR and molecular modeling techniques not only can assist CE to investigate the chiral discrimination mechanism, but also can predict and guide CE enantioseparation efficiency conversely.

Sublethal effects of the beta-blocker sotalol at environmentally relevant concentrations on the New Zealand mudsnail Potamopyrgus antipodarum.

Monitoring sublethal effects of pharmaceuticals on nontarget species in aquatic environments has become an important topic in ecotoxicology, yet few studies have been conducted concerning the effects of beta-blockers on aquatic organisms. The present study investigated the effects of the beta-blocker sotalol (SOT) at 3 environmentally relevant concentrations on life-history traits of the New Zealand mudsnail Potamopyrgus antipodarum. Based on the pharmacodynamic properties of SOT, the authors hypothesized reduced numbers of embryos in the brood pouches, decelerated growth of adult snails, and smaller size of neonates, but no effect on mortality rates of adults. Contrary to the hypothesis, the total number of embryos was significantly higher after 56 d of exposure at nominal concentrations of 0.05 µg/L and 1.0 µg/L by 107% and 73%, respectively. No differences in embryo numbers were observed at earlier time-points. Therefore, the mode of action seems to be an extension of the reproductive period rather than an increase of the embryo production. Furthermore, our results indicate a hormetic dose-response relationship, because no effects were observed at the highest test-concentration (6.5 µg/L). Mortality, growth of adult snails, and neonate sizes were not affected by the beta-blocker. Given the strong influence on reproduction, the effects of sublethal concentrations of SOT and other beta-blockers deserve better consideration in ecotoxicological risk assessment.

Characterization of carbon nanotubes decorated with NiFe2O4 magnetic nanoparticles as a novel electrochemical sensor: application for highly selective determination of sotalol using voltammetry.

A magnetic nano-composite of multiwall carbon nanotube, decorated with NiFe2O4 nanoparticles, was synthesized with citrate sol-gel method. The multiwall carbon nanotubes decorated with NiFe2O4 nanoparticles (NiFe2O4-MWCNTs) were characterized with different methods such as Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), atomic force microscopy (AFM), vibrating sample magnetometer (VSM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The new nano-composite acts as a suitable electrocatalyst for the oxidation of sotalol at a potential of 500 mV at the surface of the modified electrode. Linear sweep voltammetry exhibited two wide linear dynamic ranges of 0.5-1000 µmol L(-1) sotalol with a detection limit of 0.09 µmol L(-1). The modified electrode was used as a novel electrochemical sensor for the determination of sotalol in real samples such as pharmaceutical, patient and safe human urine.

Occurrence and removal of pharmaceuticals and hormones through drinking water treatment.

The occurrence of fifty-five pharmaceuticals, hormones and metabolites in raw waters used for drinking water production and their removal through a drinking water treatment were studied. Thirty-five out of fifty-five drugs were detected in the raw water at the facility intake with concentrations up to 1200 ng/L. The behavior of the compounds was studied at each step: prechlorination, coagulation, sand filtration, ozonation, granular activated carbon filtration and post-chlorination; showing that the complete treatment accounted for the complete removal of all the compounds detected in raw waters except for five of them. Phenytoin, atenolol and hydrochlorothiazide were the three pharmaceuticals most frequently found in finished waters at concentrations about 10 ng/L. Sotalol and carbamazepine epoxide were found in less than a half of the samples at lower concentrations, above 2 ng/L. However despite their persistence, the removals of these five pharmaceuticals were higher than 95%.

Extraction and preconcentration of beta-blockers in human urine for analysis with high performance liquid chromatography by means of carrier-mediated liquid phase microextraction.

A novel method was developed for the analysis of four beta-blockers, namely sotalol, carteolol, bisoprolol, and propranolol, in human urine by coupling carrier-mediated liquid phase microextraction (CM-LPME) to high performance liquid chromatography (HPLC). By adding an appropriate carrier in organic phase, simultaneous extraction and enrichment of hydrophilic (sotalol, carteolol, and bisoprolol) and hydrophobic (propranolol) drugs were achieved. High enrichment factors were obtained by optimizing the compositions of the organic phase, the acceptor solution, the donor solution, the stirring rate, and the extraction time. The linear ranges were from 0.05 to 10.0 mg L(-1) for sotalol and carteolol, and from 0.05 to 8.0 mg L(-1) for bisoprolol and propranolol. The limits of detection (S/N=3) were 0.01 mg L(-1) for sotalol, carteolol, and bisoprolol, and 0.005 mg L(-1) for propranolol. The relative standard deviations were lower than 6%. The developed method exhibited high analyte preconcentration and excellent sample clean-up effects with little solvent consumption and was found to be sensitive and suitable for simultaneous determination of the above four drugs spiked in human urine. Furthermore, the successful analysis of propranolol in real urine specimens revealed that the determination of beta-blockers in human urine is feasible using the present method.

Highly sensitive transient isotachophoresis sample stacking coupling with capillary electrophoresis-amperometric detection for analysis of doping substances.

A simple and effective method of capillary electrophoresis-amperometric detection (CE-AD) coupled with transient isotachophoresis (tITP) was developed for the trace determination of doping substances. Compared with the conventional capillary electrophoresis method, the maximum enhancement factor in terms of peak heights was up to 5500-fold when the tITP technique was adopted. Under the optimum conditions, the detection limit (S/N=3) for methylephedrine (MDP), celiprolol (CEL), sotalol (SOT) and indapamide (IDP) were 4.2 x 10(-14), 6.3 x 10(-13), 5.8 x 10(-14) and 9.5 x 10(-13)molL(-1), respectively. The RSDs of four analytes were 1.0-2.3% for migration time and 2.6-3.8% for peak current, respectively. The proposed method was successfully applied to determine the contents of SOT and IDP in real urine sample, and the excretion curve of IDP within 48h was also investigated. The recoveries of the four doping in urine ranged from 90.0 to 102%.

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.

Establishment of an enzyme-linked immunosorbent assay for measurement of sotalol.

We have established an enzyme-linked immunosorbent assay suitable for routine monitoring of serum levels of sotalol. Anti-sotalol antibody was obtained by immunizing rabbits with sotalol conjugated with bovine serum albumin using the N-succinimidyl ester method. An enzyme marker was similarly prepared by coupling sotalol with beta-D-galactosidase. The detection limit of sotalol by the enzyme-linked immunosorbent assay was approximately 32 ng/ml with 50-microl samples. This assay was specific for sotalol because of very slight cross-reactivity with 4-(methanesulfonylamino)benzonitrile (1.6%), but none with D,L-isoproterenol. Using this assay, drug levels were easily measured in the serum of rabbits after oral administration of sotalol at a single dose of 3 mg/kg. The enzyme-linked immunosorbent assay should be a valuable tool in therapeutic drug monitoring and pharmacokinetic studies of sotalol.

[Determination of sotalol hydrochloride by reversed-phase high performance liquid chromatography].

An RP-HPLC method for determination and detection of sotalol hydrochloride is described. The baseline separation was achieved on ODS column within 15 minutes by using 0.1% HAc-acetonitrile (80:20, V/V) as mobile phase at a flow rate 1.5 mL/min, and the wavelength was set at 227 nm. The linear range was 5-45 mg/L (r = 0.9991) and the limit of detection was 1 mg/L(S/N > 3). The intra-day and inter-day RSDs were 0.20% and 0.93% respectively.

Drug release from a porous ion-exchange membrane in vitro.

The effect of environmental ionic strength on the rate of drug release from a cation exchange membrane was evaluated. Cationic propranolol-HCl, timolol, sotalol-HCl, atenolol and dexmedetomidine-HCl and neutral diazepam were adsorbed onto a porous poly(vinylidene fluoride) (PVDF) membrane that was grafted with bioadhesive poly(acrylic acid) chains (PAA-PVDF). Despite its porosity, the PAA-PVDF membrane acted as a cation exchange membrane. The release of adsorbed drug from the PAA-PVDF membrane was investigated by using a USP rotating basket apparatus. Adsorption of cationic drugs onto the PAA-PVDF membrane tended to increase with increasing lipophilicity of the drug. A decrease in the ionic strength of the adsorption medium increased the amount of the cationic drugs adsorbed onto the membrane, but had no effect on diazepam adsorption. The release of cationic drugs from the PAA-PVDF membrane was greatly affected by the ionic strength of both the adsorption medium and the dissolution medium, while ionic strengths did not affect diazepam release. Our results suggest that the ionic strength of both the adsorption and dissolution media substantially affects the release rate of a drug that has been adsorbed onto the ion exchange membrane, primarily via electrostatic interactions, while ionic strength has no effect on the release of a drug which has been adsorbed onto the membrane via non-electrostatic forces.

Determination of sotalol in human cardiac tissue by high-performance liquid chromatography.

A sensitive and quantitative reversed-phase HPLC method for the analysis of D,L-sotalol in human atria, ventricles, blood and plasma was developed. Sotalol was determined in about 100 mg of human right atria, left ventricles, and in 500 microliters of blood and plasma samples of patients undergoing coronary bypass surgery or heart transplantation. Patients were taking 80-160 mg of sotalol as an antiarrhythmic agent. Atenolol was used as an internal standard certifying high precision of measurement. Sotalol blood and plasma concentrations correlated linearly to the obtained signals from 26.5 ng/ml to 2.12 micrograms/ml. Sotalol tissue concentrations showed linearity between 0.27 ng/mg and 10.6 ng/mg wet weight. The limit of quantitation was 0.27 ng/mg at a signal-to-noise ratio of 10. Sotalol was extracted from homogenized tissue with a buffer solution (pH9) and the remaining pellet was extracted with methanol. The methanol extract was evaporated under nitrogen and reconstituted in buffer (pH3). The whole extract was cleaned by solid-phase column extraction, eluted with methanol, evaporated again, reconstituted in the mobile phase (acetonitrile-15 mM potassium phosphate buffer pH3, 17:83, v/v) and injected onto the HPLC column (Spherisorb C6 column, 5 microns, 150 x 4.6 mm I.D.). For the detection of sotalol, the UV wavelength was set to 230 nm. Recoveries of sotalol and atenolol in atria and ventricles were 65.6 and 75.0%, respectively. Intra- and inter-assay coefficients of variation for tissue concentrations were 3.38 and 6.14%, respectively. Intra- and inter-assay accuracy for determined tissue sotalol concentrations were 94.9 +/- 6.3 and 99.6 +/- 4.1%.

Stereoselective high-performance liquid chromatographic assay for the determination of sotalol enantiomers in biological fluids.

A high-performance liquid chromatographic (HPLC) assay for determination of sotalol enantiomers in biological fluids was developed to assess the stereoselective disposition of the drug in man. Following extraction at pH 9.0 with a mixture of chloroform-isopropanol (3:1, v/v), the organic phase was evaporated to dryness and the residue derivatized with (-)-methyl chloroformate. Diastereoisomeric derivatives were resolved by HPLC (C8 column) with fluorescence detection (lambda ex = 235 nm and lambda em = 300 nm). Retention times of l- and d-sotalol derivatives were 13 and 15 min while that of the internal standard, S-(-)-atenolol, was 12.3 min. The detection limit of each enantiomer was 12.5 ng/ml using 1 ml of plasma or urine. Intra-day and inter-day coefficients of variation were less than 10% for each enantiomer in the range 0.125-2.5 micrograms/ml in plasma and 0.25-2.5 micrograms/ml in urine.

Simplified procedure for the determination of sotalol in plasma by high-performance liquid chromatography.

A simple, specific and rapid reversed-phase high-performance liquid chromatographic (HPLC) procedure for sotalol determination is described requiring small plasma volumes. The high recovery of sotalol from plasma and the high precision of measurement obviate the need for an internal standard. Plasma samples (300 microliters) were deproteinised with 50 microliters of 70% (w/w) perchloric acid in disposable glass tubes. After vortex-mixing and centrifugation, 30 microliters of 4 M K2HPO4 were added followed by gentle shaking. A 20-microliters aliquot was then injected (by autosampler) for HPLC analysis. Chromatography was performed on a glass-lined 250 mm x 4 mm 5-micron C18 steel column. The mobile phase was 6% (v/v) acetonitrile in 0.08 M KH2PO4 buffer (pH 4.6). The flow-rate was 0.8 ml/min. Detection was by fluorescence with excitation and emission wavelengths at 235 and 310 nm, respectively. The retention time for sotalol was 7.1 min. Calibration was linear from 0.16 to 10 micrograms/ml in plasma (r greater than 0.999 for detector response to sotalol). The minimum concentration for quantitation was 0.08 micrograms/ml [within assay coefficient of variation (C.V.) less than 5%]. Recovery was near quantitative (greater than 98%) and replicate (intra-assay precision was less than 5% C.V.). Analysis of samples (n = 10) at concentrations of 0.42 and 4.2 micrograms/ml gave mean values of 0.44 and 4.3 micrograms/ml, respectively. The inter-assay C.V. values were 4.5 and 2.2%, respectively. Other clinically used antiarrhythmic drugs did not interfere. This assay can be performed using other commercial C18 analytical columns by suitable adjustment of mobile phase flow-rate and acetonitrile composition.

Kinetic determination of sotalol by oxidation with sodium vanadate.

A kinetic method is described for the determination of sotalol. The method uses 0.033 M sodium vanadate to oxidize sotalol in 4 M sulphuric acid. The solution is heated at 90 degrees C and the absorbance is measured at 750 nm at a fixed time of 30 min. The concentration (c) of sotalol is calculated from the absorbance (A) by the equation: A = 0.04 + 0.0015625 c.

Determination of sotalol in human body fluids for pharmacokinetic and toxicokinetic studies using high-performance liquid chromatography.

A sensitive, reliable and discriminating assay method is reported for the determination of sotalol (4-(1-hydroxy-2-isopropylaminoethyl)methanesulfonanilide) in human plasma and urine. The assay procedure has been successfully used during pharmacokinetic studies in healthy volunteers and patients as well as during toxicokinetic analysis. For sample preparation the internal standard atenolol was added to the specimen which was then extracted with n-pentanol-chloroform (1/3) at pH 9.0 followed by re-extraction into 0.05 mol/l sulfuric acid. Chromatography with fluorimetric detection was performed on Hypersil ODS 5 micron including the addition of heptanesulfonic acid and sodium dodecyl sulfate to the mobile phase of acetonitrile-water-acetic acid (20/79/1). Calibration was linear over the ranges of 0.1 to 5.0 micrograms/ml and 0.2 to 100 micrograms/ml for plasma and urine, respectively. Over these ranges coefficients of variation were below 10%. Recovery was between 82 and 98% from plasma and between 92 and 99% from urine.

Liquid chromatographic determination of sotalol in plasma and urine employing solid-phase extraction and fluorescence detection.

A liquid chromatographic method using a solid-phase extraction procedure for the quantification of sotalol in plasma and urine is described. Sotalol is eluted from an extraction column with ethyl acetate-acetonitrile (1:2) and, after separation by reversed-phase high-performance liquid chromatography on a mu Bondapak C18 column, is quantified by fluorescence detection at excitation and emission wavelengths of 240 and 310 nm, respectively. The method has been demonstrated to be linear over the concentration ranges 10-6000 ng/ml in plasma and 0.5-100 micrograms/ml in urine. Mean inter-assay accuracy of the method for plasma ranged from 93 to 100% and for urine from 102 to 114%; precision ranged from 0.5 to 1.6% for plasma over a concentration range of 200-4000 ng/ml and for urine from 0.7 to 2.0% at concentrations of 2-50 micrograms/ml. Mass spectrometry confirmed the presence of sotalol in isolated chromatographic fractions of plasma and urine extracts from subjects given sotalol orally.

High-performance liquid chromatographic determination of sotalol in biological fluids.

A sensitive, selective and reproducible reversed-phase high-performance liquid chromatographic method is described for the quantification of sotalol in human serum and urine. Sotalol and the internal standard, atenolol, were extracted from alkalinized serum and urine (pH 9.0) into 1-butanol--chloroform (20:60, v/v). The organic phase was evaporated, and to the residue was added 0.1 M sulphuric acid (serum analysis) or mobile phase (urine analysis). The mobile phase consisted of 0.01 M phosphate buffer (pH 3.2) and acetonitrile (20:80, v/v) containing 3 mM n-octylsodium sulphate. The flow-rate was 1.5 ml/min. The retention times of atenolol and sotalol were 7 and 10 min, respectively. Ultraviolet detection at 226 nm made it possible to achieve a detection limit of 0.03 mumol/l.