Beta-blocker carteolol and oxprenolol produce cutaneous analgesia in response to needle pinpricks in the rat.

BACKGROUND: This present study was undertaken to determine whether beta-blockers produce the cutaneous analgesic effect, comparing them with the long-acting local anesthetic bupivacaine. METHODS: Using a rat model of infiltrative cutaneous analgesia, the effect of 5 beta-blockers (oxprenolol, carteolol, butaxamine, metoprolol, and acebutolol) and bupivacaine was compared and eventually combined with epinephrine. RESULTS: Among 5 beta-blockers, oxprenolol exhibited the most potent and the longest duration of cutaneous analgesia. In dose-response studies, the rank order of efficacy (ED50 [50% effective dose]) was bupivacaine (0.40 [0.35-0.47] µmol) > oxprenolol (2.33 [2.06-2.64] µmol) > carteolol (4.86 [4.27-5.53] µmol) (p< 0.01). Carteolol provoked a longer duration of analgesia (p< 0.01) than oxprenolol or bupivacaine on an equipotent basis (ED25, ED50, and ED75). Adding epinephrine 1:200,000 to drug preparations (carteolol, oxprenolol, and bupivacaine) at ED95 had a peripheral action in prolonging the duration of action. CONCLUSIONS: Oxprenolol and carteolol had greater potencies and longer durations of cutaneous analgesia than butaxamine, metoprolol, and acebutolol. Oxprenolol produced a similar duration of action when compared to bupivacaine, while carteolol had a greater duration of action than bupivacaine. Cutaneous analgesia of oxprenolol (or carteolol) plus adrenaline was greater than that of bupivacaine plus adrenaline.

The atypical ß-blocker S-oxprenolol reduces cachexia and improves survival in a rat cancer cachexia model.

BACKGROUND: Beta-blockers and selected stereoisomers of beta-blockers, like bisoprolol and S-pindolol (ACM-001), have been shown to be effective in preclinical cancer cachexia models. Here, we tested the efficacy of stereoisomers of oxprenolol in two preclinical models of cancer cachexia-the Yoshida AH-130 rat model and the Lewis lung carcinoma (LLC) mouse model. METHODS AND RESULTS: In the Yoshida AH130 hepatoma rat cancer cachexia model and compared with placebo, 50 mg/kg/d S-oxprenolol (HR: 0.49, 95% CI: 0.28-0.85, P = 0.012) was superior to 50 mg/kg/d R-oxprenolol (HR: 0.83, 95% CI 0.38-1.45, P = 0.51) in reducing mortality (= reaching ethical endpoints). Combination of the three doses (12.5, 25 and 50 mg/kg/d) that had a significant effect on body weight loss in the S-oxprenolol groups vs the same combination of the R-oxprenolol groups lead to a significantly improved survival of S-oxprenolol vs R-oxprenolol (HR: 1.61, 95% CI: 1.08-2.39, P = 0.0185). Interestingly, there is a clear dose dependency in S-oxprenolol-treated (5, 12.5, 25 and 50 mg/kg/d) groups, which was not observed in groups treated with R-oxprenolol. A dose-dependent attenuation of weight and lean mass loss by S-oxprenolol was seen in the Yoshida rat model, whereas R-oxprenolol had only had a significant effect on fat mass. S-oxprenolol also non-significantly reduced weight loss in the LLC model and also improved muscle function (grip strength 428 ± 25 and 539 ± 37 g/100 g body weight for placebo and S-oxprenolol, respectively). However, there was only a minor effect on quality of life indicators food intake and spontaneous activity in the Yoshida model (25 mg/kg/S-oxprenolol: 11.9 ± 2.5 g vs placebo: 4.9 ± 0.8 g, P = 0.013 and also vs 25 mg/kg/d R-oxprenolol: 7.5 ± 2.6 g, P = 0.025). Both enantiomers had no effects on cardiac dimensions and function at the doses used in this study. Western blotting of proteins involved in the anabolic/catabolic homoeostasis suggest that anabolic signalling is persevered (IGF-1 receptor, Akt) and catabolic signalling is inhibited (FXBO-10, TRAF-6) by S-pindolol, but not he R-enantiomer. Expression of glucose transporters Glut1 and Glut 4 was similar in all groups, as was AMPK. CONCLUSIONS: S-oxprenolol is superior to R-oxprenolol in cancer cachexia animal models and shows promise for a human application in cancer cachexia.

Diverse pharmacological properties, trial results, comorbidity prescribing and neural pathophysiology suggest European hypertension guideline downgrading of beta-blockers is not justified.

Beta-blockers have solid documentation in preventing cardiovascular complications in the treatment of hypertension; atenolol, metoprolol, oxprenolol and propranolol demonstrate proven cardiovascular prevention in hypertension mega-trials. Hypertension is characterised by activation of the sympathetic nervous system from early to late phases, which makes beta-blockers an appropriate treatment seen from a pathophysiological viewpoint, especially in patients with an elevated heart rate. Beta-blockers represent a heterogenous class of drugs with regard to both pharmacodynamic and pharmacokinetic properties. This position is manifest by reference to another clinical context, beta-blocker treatment of heart failure, where unequivocally there is no class effect (no similar benefit from all beta-blockers); there are good and less good beta-blockers for heart failure. Analogous differences in beta-blocker efficacy is also likely in hypertension. Beta-blockers are widely used for the treatment of diseases comorbid with hypertension, in approximately 50 different concomitant medical conditions that are frequent in patients with hypertension, leading to many de facto beta-blocker first choices in clinical practice. Thus, beta-blockers should be regarded as relevant first choices for hypertension in clinical practice, particularly if characterised by a long half-life, highly selective beta-1 blocking activity and no intrinsic agonist properties.SUMMARYBeta-blockers have solid documentation in preventing cardiovascular complications in the treatment of hypertension; atenolol, metoprolol, oxprenolol and propranolol demonstrate proven cardiovascular prevention in hypertension mega-trialsHypertension is characterised by activation of the sympathetic nervous system from early to late phases, which makes beta-blockers an appropriate treatment seen from a pathophysiological viewpoint, especially in patients with an elevated heart rateBeta-blockers represent a heterogenous class of drugs with regard to both pharmacodynamic and pharmacokinetic propertiesThis position is manifest by reference to another clinical context, beta-blocker treatment of heart failure, where unequivocally there is no class effect (no similar benefit from all beta-blockers); there are good and less good beta-blockers for heart failureAnalogous differences in beta-blocker efficacy is also likely in hypertensionBeta-blockers are widely used for the treatment of diseases comorbid with hypertension, in approximately 50 different concomitant medical conditions that are frequent in patients with hypertension, leading to many de facto beta-blockers first choices in clinical practiceThese observations, in totality, inform our opinion that beta-blockers are relevant first choices for hypertension in clinical practice and this fact needs highlightingFurther, these arguments suggest European hypertension guideline downgrading of beta-blockers is not justified.

Identification of Alprenolol Hydrochloride as an Anti-prion Compound Using Surface Plasmon Resonance Imaging.

Prion diseases are transmissible neurodegenerative disorders of humans and animals, which are characterized by the aggregation of abnormal prion protein (PrPSc) in the central nervous system. Although several small compounds that bind to normal PrP (PrPC) have been shown to inhibit structural conversion of the protein, an effective therapy for human prion disease remains to be established. In this study, we screened 1200 existing drugs approved by the US Food and Drug Administration (FDA) for anti-prion activity using surface plasmon resonance imaging (SPRi). Of these drugs, 31 showed strong binding activity to recombinant human PrP, and three of these reduced the accumulation of PrPSc in prion-infected cells. One of the active compounds, alprenolol hydrochloride, which is used clinically as a ß-adrenergic blocker for hypertension, also reduced the accumulation of PrPSc in the brains of prion-infected mice at the middle stage of the disease when the drug was administered orally with their daily water from the day after infection. Docking simulation analysis suggested that alprenolol hydrochloride fitted into the hotspot within mouse PrPC, which is known as the most fragile structure within the protein. These findings provide evidence that SPRi is useful in identifying effective drug candidates for neurodegenerative diseases caused by abnormal protein aggregation, such as prion diseases.

Comparative efficacy of ß-blockers on mortality and cardiovascular outcomes in patients with hypertension: a systematic review and network meta-analysis.

The differential efficacy of lipophilic and hydrophilic ß-blockers on clinical outcomes has not been investigated. We sought to compare the effects of lipophilic and hydrophilic ß-blockers on mortality and cardiovascular outcomes by conducting a comprehensive systematic review and network meta-analysis. MEDLINE/PubMed, EMBASE, and the Cochrane Database were searched for all dates to January 5, 2015, for randomized trials with comparisons between all ß-blockers or between ß-blockers and other antihypertensive agents. Mortality and cardiovascular outcomes were also reported. Characteristics of each study and associated clinical outcomes were extracted, including all-cause mortality, coronary heart disease, stroke, and cardiovascular death. Thirteen trials with 90,935 participants were included, focusing on lipophilic ß-blockers (metoprolol, propranolol, and oxprenolol) and a hydrophilic ß-blocker (atenolol). In this review, lipophilic ß-blockers showed a significant reduction for the risk of cardiovascular mortality (odds ratio [OR] 0.72, 95% confidence interval [CI; 0.54-0.97]) compared with hydrophilic ß-blocker, and lipophilic ß-blockers showed decreased trend for the risk of all-cause mortality (OR 0.86, 95% CI [0.72-1.03]) and coronary heart disease (OR 0.88, 95% CI [0.64-1.23]). When the risk of stroke was evaluated using age stratification, lipophilic ß-blockers showed a significant reduction in the risk of stroke (OR 0.63, 95% CI [0.41-0.99]) compared with hydrophilic ß-blocker in patients aged <65 years.

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.

Molecular dynamics simulations of Oxprenolol and Propranolol in a DPPC lipid bilayer.

Extensive microscopic molecular dynamics simulations have been performed to study the effects of tow ß-blocker drugs (Propranolol, Oxprenolol) on fully hydrated dipalmitoylphosphatidylcholine (DPPC) in the fluid phase at 323K. Simulation of 4 systems containing varying concentrations of drugs was carried out. For the purpose of comparison, a fully hydrated DPPC bilayer without drugs was also studied at the same level of simulation technique which has been done on 4 other systems. The length of each simulation was 100ns. The effects of concentrations of both drugs were analyzed on lipid bilayer properties, such as electrostatic potential, order parameter, diffusion coefficients, and hydrogen bond formation, etc. Penetration of water in the bilayer system was also investigated using radial distribution function analysis. Efficacy of varying concentrations of both drugs has no significant effect on P-N vector. Consistent with experimental results, by increasing the concentration of Propranolol, the thickness of the bilayer was increased.

Restricted access molecularly imprinted polymers obtained by bovine serum albumin and/or hydrophilic monomers' external layers: a comparison related to physical and chemical properties.

Molecularly imprinting polymers (MIPs) can be modified with external layers in order to obtain restricted access molecularly imprinted polymers (RAMIPs) able to exclude macromolecules and retain low weight compounds. These modifications have been frequently achieved using hydrophilic monomers, chemically bound on the MIP surface. Recently, our group proposed a new biocompatible RAMIP based on the formation of a bovine serum albumin coating on the surface of MIP particles. This material has been used to extract drugs directly from untreated human plasma samples, but its physicochemical evaluation has not been carried out yet, mainly in comparison with RAMIPs obtained by hydrophilic monomers. Thus, we proposed in this paper a comparative study involving the surface composition, microscopic aspect, selectivity, binding kinetics, adsorption and macromolecule elimination ability of these different materials. We concluded that the synthesis procedure influences the size and shape of particles and that hydrophilic co-monomer addition as well as coating with BSA do not alter the chemical recognition ability of the material. The difference between imprinted and non-imprinted polymers' adsorption was evident (suggesting that imprinted polymers have a better capacity to bind the template than the non-imprinted ones). The Langmuir model presents the best fit to describe the materials' adsorption profile. The polymer covered with hydrophilic monomers presented the best adsorption for the template in an aqueous medium, probably due to a hydrophilic layer on its surface. We also concluded that an association of the hydrophilic monomers with the bovine serum albumin coating is important to obtain materials with higher capacity of macromolecule exclusion.

A comparative ex vivo drug permeation study of beta-blockers through porcine buccal mucosa.

Apparent permeability coefficients (kp) of a series of beta-blockers: acebutolol, atenolol, labetalol, metoprolol, oxprenolol and propranolol, through porcine buccal mucosa were determined. The aim of the study was to determine the permeation parameters (apparent permeability coefficient, kp; flux, J; and lag time, TL) as a measure of the intrinsic permeability of porcine buccal mucosa to these drugs, in order to predict the efficacy of their possible administration through human buccal mucosa. A positive linear correlation was observed between the apparent permeability coefficient, kpand the partition coefficient, P. Oxprenolol and propranolol are the drugs that presented the highest values of kp: 0.3231×10(2) cm/h and 0.5666×10(2) cm/h, respectively. Multiple linear regression (MLR) using least square estimation was performed on the data set with logkpas dependent variable and the descriptors as predictor variables. The potential systemic capacity after a buccal administration was predicted by estimating the plasma concentrations at steady-stated (Css). Considering the entire process of permeation ex vivo, propranolol and oxprenolol would seem to be the best candidates for administration through the buccal mucosa.

Interactions of beta-blockers with model lipid membranes: molecular view of the interaction of acebutolol, oxprenolol, and propranolol with phosphatidylcholine vesicles by time-dependent fluorescence shift and molecular dynamics simulations.

Since pharmacokinetic and pharmacodynamic activities of drugs are often related to their interactions with biomembranes, it is of high interest to establish an approach for the characterization of these interactions at the molecular level. For the present study, beta-blockers (oxprenolol, propranolol, and acebutolol) were selected due to their well described nonspecific membrane effects (NME). Their interactions with model lipid membranes composed of palmitoyloleoylphosphatidylcholine (POPC) were studied using Time-Dependent Fluorescence Shift (TDFS) and Generalized Polarization (GP) as well as molecular dynamics (MD) simulations. Liposomal vesicles were labeled with fluorescent membrane polarity probes (Laurdan, Prodan, and Dtmac). Increasing beta-blocker concentrations (0-10 mM for acebutolol and oxprenolol, and 0-1.5 mM for propranolol) significantly rigidifies the lipid bilayer at the glycerol and headgroup level, which was detected in the steady-state and in the time-resolved fluorescence data. The effects of propranolol were considerably stronger than those of the two other beta-blockers. The addition of fluorescent probes precisely located at different levels within the lipid bilayer revealed the insertion of the beta-blockers into the POPC bilayer at the glycerol backbone level, which was further confirmed by MD simulations in the case of propranolol.

Simultaneous and sensitive capillary electrophoretic enantioseparation of three ß-blockers with the combination of achiral ionic liquid and dual CD derivatives.

Successful simultaneous enantioseparation and sensitive determination of three ß-blockers (PIN, OX and PRO), have been achieved by capillary electrophoresis using an achiral ionic liquid, [GTMA]Cl, as a modifier to cooperate with dual CDs containing DM-ß-CD and TM-ß-CD. The influence of aIL was investigated in details, including various aILs, the concentration of aIL and molar ratio of aIL to CD. The ratio of DM-ß-CD to TM-ß-CD in dual CDs was also discussed. DM-ß-CD and TM-ß-CD favor the enantioseparations of PIN/OX and PRO, respectively. Meanwhile, the presence of [GTMA]Cl was found to play a key role in enantioseparations, and it widened the scope of application of DM-ß-CD and TM-ß-CD. Furthermore, FESI as an effective on-line sample enrichment technique was developed to improve the detection sensitivity. Under the optimum conditions, the detection limits of the three pairs of enantiomers range from 0.10 to 0.65 nM, which are much lower than those in the conventional methods. Eventually, the proposed method was successfully applied to the analysis of spiked urine sample with good recoveries.

The interactivities with lipid membranes differentially characterize selective and nonselective beta1-blockers.

BACKGROUND AND OBJECTIVE: beta-Adrenoceptor-blocking agents have been used for perioperative management during anaesthesia, in which selective beta1-blockers are advantageous over nonselective beta-blockers. Apart from the different affinity for beta-adrenoceptors, beta1-blockers were differentially characterized in light of their different interaction with lipid membranes. METHODS: Selective (atenolol, metoprolol and esmolol) and nonselective (alprenolol, oxprenolol and propranolol) beta1-blockers were reacted at 0.2-1 mmol l with 1,2-dipalmitoylphosphatidylcholine liposomes and biomimetic membranes consisting of phospholipids, sphingolipid and cholesterol. Their membrane interactivities were comparatively determined using the potency to modify membrane fluidity by measuring fluorescence polarization. Their relative hydrophobicities were evaluated by reversed-phase liquid chromatography. RESULTS: The chromatographic evaluation divided the tested drugs into more hydrophobic ones containing nonselective beta-blockers and less hydrophobic ones containing selective beta1-blockers. Nonselective beta-blockers, but not selective beta1-blockers, fluidized liposomal membranes, with the potency being oxprenolol < alprenolol < propranolol. Membrane-active alprenolol preferentially acted on the hydrophobic deeper regions of phospholipid bilayers. The potency of nonselective beta-blockers to fluidize biomimetic membranes was greatest in propranolol, followed by alprenolol and oxprenolol, whereas all selective beta1-blockers were inactive. CONCLUSION: The membrane-fluidizing effects of beta-blockers are correlated with their relative hydrophobicities and their respective conformations to perturb the alignment of phospholipid acyl chains. The membrane-interacting characteristics differentiate beta-blockers as nonselective propranolol, alprenolol and oxprenolol vs. beta1-selective atenolol, metoprolol and esmolol. Such differentiation reflects not only the structural difference but also the beta-adrenoceptor-blocking difference. The membrane fluidization may be partly responsible for the nonselective blockade of beta-adrenoceptors.

Quantitative determination of propranolol by ultraviolet HPLC in human plasma.

Many previous published methods for the quantitative determination of propranolol (PRN) in human plasma have poor recoveries and were not validated according to the FDA guideline. The aim of this study is to develop a simple HPLC method for detecting PRN in human plasma and to validate it so that it can be applied to a clinical study. Chromatographic separation was achieved using a mixture of a mobile phase consisting of 160 ml water, 180 ml methanol, 70 ml acetonitrile, 2.5 ml acetic acid, and 125 microl triethylamine (v/v). The pH of the whole mixture was adjusted to 3.4. A flow rate of 0.5 ml/min was employed throughout with a 15 microl injection volume. Detection was done using a UV detector at 291 nm. The validated method was linear for concentrations ranging from 15-180 ng/ ml with a good separation and specificity for both PRN and its internal standard, oxprenolol (OXP), with excellent recoveries, precision, and accuracies. The limit of detection (LOD) and limit of quantification (LOQ) were 1 and 10 ng/ml, respectively. The stability studies demonstrated that PRN is stable in the autosampler vials and also up to 3.5 months. To the authors' knowledge, the recovery, that ranged between 97.9-102.7%, is the highest among all previously reported methods that used HPLC with UV detection. The developed and validated method for PRN analysis is excellent and applicable to a clinical study.

High frequency controlled capsules with integrated gas producing cells.

In the present investigations, a new high frequency remote-controlled capsule has been developed in which the mechanical energy to empty a drug reservoir is generated by a miniature gas producing cell. If the poles of the gas producing cell are connected by an electric circuit, the gas production starts. The rate of gas production can be regulated by a resistor in the electric circuit and by the duration of activation of the system. To get a remote control, we developed a small receiver which is located inside the capsule. The receiver consists of an oscillating circuit, which is in resonance with an external 24 MHz high frequency transmitter. A MOSFET transistor acts as a switch in the electric circuit to start the gas production. Release experiments with oxprenolol show that different release patterns can be obtained.

Determination of selected beta-receptor antagonists in biological samples by solid-phase extraction with cholesterolic phase and LC/MS.

A new method is presented for the determination of five selected beta-receptor antagonists by HPLC, which emphasizes sample preparation via retention on a new type of silica gel sorbent used for solid-phase extraction (SPE). Sorbents of this type were obtained by the chemical modification of silica gels of various porosities by cholesterol ligands. The cholesterol-based packing material was investigated by spectroscopic methods and elemental analysis. The recoveries obtained with the extraction procedure were optimum over a relatively broad sample pH range (3.08-7.50). Analytical factors such as the sample loading, the washing step and elution conditions, the concentration of beta-receptor antagonists to be extracted, and the type of sorbent were found to play significant roles in the sample preparation procedure and would therefore need to be controlled to achieve optimum recoveries of the analytes. Under optimum conditions, the recoveries of nadolol, acebutolol, esmolol, oxprenolol and propranolol from spiked buffers, blood and urine were reproducible and dependent on the polarity or hydrophilicity of the compounds. The above analytes were determined by reverse-phase high-performance liquid chromatography (HPLC) with UV and ESI-ion trap mass spectrometry (MS) detection. The described method was found to be suitable for the routine measurement of compounds that are both polar and basic, and can be applied for the analysis of biological samples such as urine and blood in clinical, toxicological or forensic laboratories. The recovery measurements were performed on spiked human urine and serum, and on real samples of mouse blood serum.

Optimization of 12 chiral analytes with 8 polymeric surfactants.

This manuscript discusses the results of studies that were performed to determine optimum capillary electrophoresis (CE) conditions for the enantiomeric resolution of twelve chiral analytes with eight amino acid based polymeric surfactants. The parameters that were optimized include pH, buffer type, and concentration of surfactant. The results indicated that the optimum conditions for enantiomeric separations with the amino acid based polymeric surfactants examined in this study using CE were analyte dependent, not surfactant dependent. In other words, the optimum conditions for a particular analyte were the same for all the amino acid based polymeric surfactants examined in this study. The results of these studies indicate that when using a large group of related amino acid based polymeric surfactants only a few surfactants need to be optimized for each analyte under study. These studies were limited to anionic surfactants that contain the amino acids glycine, L-alanine, L-valine, and L-leucine only. No inference can be necessarily drawn about surfactants containing other types of amino acids such as threonine and serine, which contain extra heteroatoms, or phenylalanine that has an aromatic moiety.

Principles for different modes of multiple-injection CZE.

This paper introduces four different modes of multiple-injection CZE (MICZE). The validity of these MICZE models was evaluated by the experimental data. Prior to the application of MICZE, the electrophoretic conditions are developed in the single-injection mode by adjusting different experimental parameters such as pH, type and concentration of buffer additives and temperature. Based on the migration time difference (Deltatmig) between the analyte and the internal standard or injection marker, one or more MICZE modes can be employed. The injection marker is added to the sample to compensate for injection-volume fluctuations. The inter-plug distance is regulated by applying an electrical field over the capillary for a short period of time between each injection. After the final injection, the separation is completed by electrophoresis for a time period corresponding to that in the single-injection mode.

Quantitative determination of salbutamol in tablets by multiple-injection capillary zone electrophoresis.

A multiple-injection capillary zone electrophoresis (MICZE) method has been developed for the assay of salbutamol in Ventoline Depot tablets (GlaxoSmithKline). In the developed method, seven sample sets, each consisting of three samples, were sequentially injected into the capillary and analyzed within a single run. This enabled a total of twenty-one sequential injections, i.e., six standards and fifteen samples, containing salbutamol and the injection marker oxprenolol. The injected sample plugs were separated by plugs of background electrolyte, through application of a short-term voltage (30kV) over the capillary for different time periods, i.e., t(PE1) and t(PE2). The samples in each set were isolated from each other by partial electrophoresis for 2.35min (t(PE1)), while the sample sets were separated for 10.50min (t(PE2)). After the final injection, all the applied samples were subjected to electrophoresis for a time period corresponding to that in conventional single-injection CZE. The method was validated regarding linearity, accuracy, precision and robustness before it was applied to the determination of salbutamol in 15 tablets of Ventoline Depot with a labeled content of 8mg salbutamol. The average salbutamol content was determined to 7.8mg (+/-0.3mg) from simultaneous analyses of the 15 different tablets.

Enantiomeric separation by using nano-liquid chromatography with on-column focusing.

The present study shows a new nano-liquid chromatographic method for beta-blocker enantiomers' separation. This method consists of using a capillary column packed with silica particles which were chemically modified with vancomycin. On-column focusing allowed to inject relatively high sample volumes (1500 nL) increasing method sensitivity. The studied racemic compounds, namely atenolol, propranolol, oxprenolol, and metoprolol were dissolved in methanol and injected for chromatographic separation. The effect of injected sample volume was studied in the range of 50-2100 nL. Peak height of the two alprenolol enantiomers increased linearly up to 1500 nL. This volume was injected for validation and sample analysis. Under optimal experimental conditions, LODs and LOQs (LOD and LOQ for each alprenolol enantiomers) were 9.0 and 15.6 ng/mL, respectively. Calibration curves were linear in the studied range (9-250 ng/mL). The optimized method was applied to the analysis of a human plasma sample spiked with racemic alprenolol.

Study on chiral resolution of three beta-blockers by affinity electrokinetic chromatography.

The chiral resolution of three beta-blockers including propranolol, pindolol and oxprenolol, was studied by affinity electrokinetic chromatography. The effect of various chiral selectors and some key parameters including buffer pH, buffer concentration, capillary temperature and applied voltage were carefully studied, respectively. At optimum condition, based on the signal-to-noise ratio of 3, the detection limits for the simple resolution and chiral resolution were found to be 1.0x10(-5) and 4.0 x 10(-5)M, respectively. In addition, the interactions of these beta-blockers with bovine serum albumin (BSA) were studied and the binding constant (K(a)) between BSA and each of beta-blockers were calculated. Based on linear correlation coefficient, it can be concluded that the binding ratio of pindolol (oxprenolol) combining with BSA is 1:1, and that the binding number of propranolol interacting with BSA deviates one.