Capillary isotachophoresis with electrospray-ionization mass-spectrometric detection: Cationic electrolyte systems in the medium-alkaline range for selective analysis of medium strong bases.

This work extends the present working range of isotachophoresis (ITP) with electrospray-ionization mass-spectrometric (ESI-MS) detection and describes for the first time a functional cationic electrolyte system for analyses at medium-alkaline pH. So far no ITP-MS application was published on the analysis of medium strong bases although there is a broad spectrum of potential analytes like biogenic amines, alkaloids or drugs, where this technique promises interesting gains in both sensitivity and specificity. The presented results include a selection of suitable sufficiently volatile ESI-compatible system components, discussion of factors affecting system properties, and recommendations for functional ITP electrolyte systems. Theoretical conclusions based on calculations and computer simulations are confirmed by experiments with a model mixture of beta-blockers. Practical applicability of the method is demonstrated on the example of analysis of sotalol in dried blood spots where direct injection of aqueous extract, ITP stacking and MS detection provide a fast, simple and sensitive technique with limits of quantitation on the sub-nM level.

High-throughput quantification of ten antiarrhythmic drugs in human plasma using UPLC-MS/MS.

In this paper we present an FDA validated method to analyze ten antiarrhythmic drugs (atenolol, bisoprolol, carvedilol, diltiazem, flecainide, lidocaine, metoprolol, propranolol, sotalol and verapamil). A simple and fast sample preparation protocol with protein precipitation followed by ultra performance liquid chromatography (UPLC) for chromatographic separation and mass spectrometric detection applying electrospray ionization (ESI+) and selected reaction monitoring mode (MS/MS) was used. Only 50 µl plasma sample is needed for the simultaneous quantification of all compounds within a 5 min run-to-run analysis time. Sotalol-D6, carvedilol-D5 and verapamil-D6 were used as internal standards. The method was validated according to the FDA guidelines. Correlation coefficients were higher than 0.998 for all compounds. Intra- and interday accuracies were within 15 CV(%) for all analytes. The method is currently successfully applied for routine analysis in our hospital.

Antenatal Therapy for Fetal Supraventricular Tachyarrhythmias: Multicenter Trial.

BACKGROUND: Standardized treatment of fetal tachyarrhythmia has not been established. OBJECTIVES: This study sought to evaluate the safety and efficacy of protocol-defined transplacental treatment for fetal supraventricular tachycardia (SVT) and atrial flutter (AFL). METHODS: In this multicenter, single-arm trial, protocol-defined transplacental treatment using digoxin, sotalol, and flecainide was performed for singleton pregnancies from 22 to <37 weeks of gestation with sustained fetal SVT or AFL ≥180 beats/min. The primary endpoint was resolution of fetal tachyarrhythmia. Secondary endpoints were fetal death, pre-term birth, and neonatal arrhythmia. Adverse events (AEs) were also assessed. RESULTS: A total of 50 patients were enrolled at 15 institutions in Japan from 2010 to 2017; short ventriculoatrial (VA) SVT (n = 17), long VA SVT (n = 4), and AFL (n = 29). One patient with AFL was excluded because of withdrawal of consent. Fetal tachyarrhythmia resolved in 89.8% (44 of 49) of cases overall and in 75.0% (3 of 4) of cases of fetal hydrops. Pre-term births occurred in 20.4% (10 of 49) of patients. Maternal AEs were observed in 78.0% (39 of 50) of patients. Serious AEs occurred in 1 mother and 4 fetuses, thus resulting in discontinuation of protocol treatment in 4 patients. Two fetal deaths occurred, mainly caused by heart failure. Neonatal tachyarrhythmia was observed in 31.9% (15 of 47) of neonates within 2 weeks after birth. CONCLUSIONS: Protocol-defined transplacental treatment for fetal SVT and AFL was effective and tolerable in 90% of patients. However, it should be kept in mind that serious AEs may take place in fetuses and that tachyarrhythmias may recur within the first 2 weeks after birth.

Telemetered common marmosets is useful for the assessment of electrocardiogram parameters changes induced by multiple cardiac ion channel inhibitors.

The objective of this study is to assess the response of telemetered common marmosets to multiple cardiac ion channel inhibitors and to clarify the usefulness of this animal model in evaluating the effects of drug candidates on electrocardiogram (ECG). Six multiple cardiac ion channel inhibitors (sotalol, astemizole, flecainide, quinidine, verapamil and terfenadine) were orally administered to telemetered common marmosets and changes in QTc, PR interval and QRS duration were evaluated. Drugs plasma levels were determined to compare the sensitivity in common marmosets to that in humans. QTc prolongation was observed in the marmosets dosed with sotalol, astemizole, flecainide, quinidine, verapamil and terfenadine. PR prolongation was noted after flecainide and verapamil administration, and QRS widening occurred following treatment with flecainide and quinidine. Drugs plasma levels associated with ECG changes in marmosets were similar to those in humans, except for verapamil-induced QTc prolongation. Verapamil-induced change is suggested due to body temperature decrease. These results indicate that telemetered common marmoset is a useful animal for evaluation of the ECG effects of multiple cardiac ion channel inhibitors and the influence of body temperature change should be considered in the assessment.

Pharmacokinetics and electrophysiological effects of sotalol hydrochloride in horses.

BACKGROUND: Arrhythmias in horses may require long-term anti-arrhythmic therapy. Unfortunately, oral anti-arrhythmic drugs for use in horses are currently scarce. In human patients and small animals, sotalol, a ß-blocker with class III anti-arrhythmic properties, is often used for long-term treatment. OBJECTIVES: To determine the pharmacokinetics of sotalol at multiple oral dosages in unfasted horses, as well as the effects on electro- and echocardiographic measurements, right atrial and ventricular monophasic action potential (MAP) and effective refractory period (ERP). STUDY DESIGN: Placebo controlled, double-blinded experiment. MATERIALS AND METHODS: Six healthy, unfasted Warmblood horses were given either 0, 2, 3 or 4 mg/kg bodyweight (bwt) sotalol orally (PO) twice daily (bid) for 9 days in a randomised cross-over design. Echocardiography and surface electrocardiography were performed and plasma concentrations of sotalol and right atrial and right ventricular MAPs and ERPs were determined at steady-state conditions. Statistical analysis was performed using a repeated measures univariate analysis with post hoc Bonferroni corrections. RESULTS: Calculated mean steady-state plasma concentrations determined by nonlinear mixed-effect modelling were 287 (range 234-339), 409 (359-458) and 543 (439-646) ng/mL for 2, 3 and 4 mg/kg bwt sotalol PO bid respectively. Sotalol significantly increased the QT interval and ERPs, but, despite increasing plasma concentrations, higher dosages did not result in a progressive increase in QT interval or ERPs. Echocardiographic and other electrocardiographic measurements did not change significantly. MAP durations at 90% repolarisation were not significantly different during sotalol treatment. Besides transient local sweating, no side effects were noted. MAIN LIMITATIONS: Study size and ad libitum feeding of hay. CONCLUSIONS: Sotalol at a dose of 2, 3 and 4 mg/kg bwt PO bid increases the QT interval and ERP and might be a useful drug for long-term anti-arrhythmic therapy in horses.

Electromembrane extraction of polar basic drugs from plasma with pure bis(2-ethylhexyl) phosphite as supported liquid membrane.

Electromembrane extraction (EME) of polar basic drugs from human plasma was investigated for the first time using pure bis(2-ethylhexyl) phosphite (DEHPi) as the supported liquid membrane (SLM). The polar basic drugs metaraminol, benzamidine, sotalol, phenylpropanolamine, ephedrine, and trimethoprim were selected as model analytes, and were extracted from 300 µL of human plasma, through 10 µL of DEHPi as SLM, and into 100 µL of 10 mM formic acid as acceptor solution. The extraction potential across the SLM was 100 V, and extractions were performed for 20 min. After EME, the acceptor solutions were analyzed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV). In contrast to other SLMs reported for polar basic drugs in the literature, the SLM of DEHPi was highly stable in contact with plasma, and the system-current across the SLM was easily kept below 50 µA. Thus, electrolysis in the sample and acceptor solution was kept at an acceptable level with no detrimental consequences. For the polar model analytes, representing a log P range from -0.40 to 1.32, recoveries in the range 25-91% were obtained from human plasma. Strong hydrogen bonding and dipole interactions were probably responsible for efficient transfer of the model analytes into the SLM, and this is the first report on efficient EME of highly polar analytes without using any ionic carrier in the SLM.

Quantification of ventricular repolarization heterogeneity during moxifloxacin or sotalol administration using [Formula: see text]-index.

Drug-induced alterations of ventricular heterogeneity must be limited to avoid induction of lethal ventricular arrhythmias. In here, a new parameter called [Formula: see text]-index, able to measure the standard deviation of myocites' repolarization times, was evaluated after moxifloxacin and sotalol administration. The two drugs are known to provide different alteration of the QT interval length ranging from subtle (moxifloxacin) to evident (sotalol). In fact, while the former is employed as active-comparator in thorough QT studies, the latter might induce torsades de pointes. 24 h Holter ECGs of 39 (sotalol) and 68 (moxifloxacin) healthy subjects were retrospectively analyzed. The recordings were performed after infusion of the drugs and after the placebo (moxifloxacin) or at baseline (sotalol). The corrected QT interval (QTc) was included as well in the study, for a direct comparison. In both populations, [Formula: see text]-index and QTc increased along with the drugs' serum concentration and were statistically different from values in the placebo arm or at baseline (p < 0.05).With sotalol, the maximum value of [Formula: see text]-index occurred, on average, after 5.64 h from the infusion, whereas for QTc after about 4.27 h. The two metrics displayed evident changes ([Formula: see text]-index: 27.79 ms ± 4.89 ms versus 60.13 ms ± 18.52 ms; QT corrected: 387.07 ms ± 19.84 ms versus 437.76 ± 32.05 ms; p < 0.05). Regarding moxifloxacin, maximum values were reached, on average, 5.01 h after administration for [Formula: see text]-index (30.70 ms ± 8.32 ms versus 40.48 ms ± 7.61 ms; p < 0.05), and 4.37 h for QTc (404.29 ms ± 29.05 ms versus 426.77 ± 36.67 ms; p < 0.05). They were statistically different from baseline values. With both drugs, the maximal percent variation after administration was higher for [Formula: see text]-index than QTc (moxifloxacin: 34.56% ± 24.60% versus 5.56% ± 2.98% ; sotalol: 114.77% ± 33.15% versus 12.13% ± 2.85% ; p < 0.05).The study suggests that the standard deviation of the ventricular repolarization times, as quantified by the [Formula: see text]-index, might be an effective measure of spatial heterogeneity.

A simple and sensitive LC-MS/MS method for the determination of sotalol in rat plasma.

A sensitive, rapid and robust HPLC method with tandem mass spectrometry (HPLC/MS/MS) detection has been developed and validated for the quantification of sotalol in rat plasma. Plasma samples were precipitated with acetonitrile before analysis. The chromatographic separation was performed on an Atlantis hydrophilic interaction liquid chromatography Silica column (50 × 2.1 mm, 3 µm) with a gradient mobile phase of 10 mm NH4 COOH (containing 0.2% of formic acid) as buffer A and acetonitrile as mobile phase B. Sotalol (m/z 273.2 → 255.1) and atenolol (the internal standard, IS, m/z 267.2 → 190.1) were monitored under positive ionization mode with 5500 QTRAP. Retention time of sotalol and the IS were 2.69 and 3.43 min, respectively. The linear range was 5-500 nm based on the analysis of 0.1 mL of plasma. The intrabatch precision ranged from 1.2 to 6.1%, and the inter-batch precision was from 3.3 to 6.5%. The coefficient of variation of IS-normalized matrix factor was 7.6%. Experiments for stability were performed and the analyte was sufficiently stable. A run time of 6 min for each injection made it possible to analyze a high throughput of plasma samples. The assay was successfully applied to the determination of sotalol in rat plasma after a micro-dose oral administration.

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.

QT prolongation and serum sotalol concentration are highly correlated following intravenous and oral sotalol.

OBJECTIVES: The aim of this study was to evaluate the correlation between QT interval (QT) and serum sotalol concentration following a single low dose of oral and intravenous sotalol. METHODS: Fifteen healthy volunteers received 75 mg intravenous sotalol over 2.5 h and 80 mg oral sotalol in a random order. Serum sotalol concentrations and 12-lead electrocardiograms were obtained simultaneously at baseline and 7 times following dosings. Rate-corrected QT (QTc) was calculated by the Bazett, Fridericia and Framingham formulas. Linear regression analysis was performed between sotalol concentrations and QT measurements. RESULTS: Significant QT prolongation was seen at very low sotalol doses and serum concentrations. QTc intervals calculated by the Framingham and Fridericia formulas showed the strongest and virtually identical correlations with serum sotalol concentration (r >or= 0.97, p < 0.001) following oral and intravenous administrations. The equation QTc = 0.0342 (sotalol concentration) + 398 closely predicted actual QTc at any sotalol concentration. CONCLUSIONS: A strong correlation was observed between serum sotalol concentration and QTc prolongation across the entire concentration range. Low-dose sotalol caused significant QT prolongation. At similar concentrations, intravenous and oral sotalol caused similar QT and QTc effects. Knowing the QT effect can be used to guide further dose increase.

Combination therapy with mexiletine and sotalol suppresses inherited ventricular arrhythmias in German shepherd dogs better than mexiletine or sotalol monotherapy: a randomized cross-over study.

OBJECTIVES: To determine the spontaneous variability of ventricular arrhythmias (VA) and evaluate anti-arrhythmic efficacy of mexiletine, sotalol, and a mexiletine-sotalol combination in German shepherd dogs (GSD) with inherited arrhythmias. ANIMALS, MATERIALS AND METHODS: 12 affected GSD, median age 20 weeks, received mexiletine (8 mg/kg PO q8 h), sotalol (2.5 mg/kg PO q12 h), and combination therapy for 6 days in random order. Pre- and post-treatment 24 h Holter recordings were acquired, allowing determination of VA variability and reduction in 24 h VA for each treatment. Drug concentrations during each arm were measured. RESULTS: An anti-arrhythmic effect could be inferred if ventricular premature complexes (VPC), ventricular couplets (V(cpl)), ventricular tachycardia runs (VT(runs)) and total ventricular ectopy (VE(tot)) frequency were reduced by 61%, 97%, 98%, and 63% (1 control Holter model), by 53%, 94%, 95%, and 54% (4 control Holter model) and by 54%, 95%, 96% and 56% (3 control Holter model). Combination therapy reduced VPC and VE(tot) in more dogs (5/12 and 6/12) than mexiletine (1/11 and 2/11) or sotalol (2/9 and 1/9) (p < 0.05). The combination therapy reduced the mean number of VPC, V(cpl), and VE(tot). Sotalol monotherapy produced an increase in VT(runs). Plasma mexiletine concentration was higher during combination therapy than with monotherapy. CONCLUSIONS: Combination therapy reduced VPC in affected GSD. Sotalol monotherapy increased VT(runs). Combination therapy increased plasma mexiletine concentrations.

The time course of new T-wave ECG descriptors following single- and double-dose administration of sotalol in healthy subjects.

INTRODUCTION: The aim of the study was to assess the time course effect of IKr blockade on ECG biomarkers of ventricular repolarization and to evaluate the accuracy of a fully automatic approach for QT duration evaluation. METHODS: Twelve-lead digital ECG Holter was recorded in 38 healthy subjects (27 males, mean age = 27.4 + or - 8.0 years) on baseline conditions (day 0) and after administration of 160 mg (day 1) and 320 mg (day 2) of d-l sotalol. For each 24-hour period and each subject, ECGs were extracted every 10 minutes during the 4-hour period following drug dosage. Ventricular repolarization was characterized using three biomarker categories: conventional ECG time intervals, principal component analysis (PCA) analysis on the T wave, and fully automatic biomarkers computed from a mathematical model of the T wave. RESULTS: QT interval was significantly prolonged starting 1 hour 20 minutes after drug dosing with 160 mg and 1 hour 10 minutes after drug dosing with 320 mg. PCA ventricular repolarization parameters sotalol-induced changes were delayed (>3 hours). After sotalol dosing, the early phase of the T wave changed earlier than the late phase prolongation. Globally, the modeled surrogate QT paralleled manual QT changes. The duration of manual QT and automatic surrogate QT were strongly correlated (R(2) = 0.92, P < 0.001). The Bland and Altman plot revealed a nonstationary systematic bias (bias = 26.5 ms + or - 1.96*SD = 16 ms). CONCLUSIONS: Changes in different ECG biomarkers of ventricular repolarization display different kinetics after administration of a potent potassium channel blocker. These differences need to be taken into account when designing ventricular repolarization ECG studies.

Intrapericardial delivery of amiodarone and sotalol: atrial transmural drug distribution and electrophysiological effects.

Amiodarone and sotalol are frequently used in the treatment of atrial fibrillation. However, oral and intravenous (IV) therapy with these drugs has suboptimal efficacy and is associated with serious extracardiac side effects. We hypothesized that intrapericardial (IPC) delivery produces antiarrhythmic effects at lower plasma drug concentrations than IV delivery. Goats (n = 27) were randomised into 5 groups receiving either IPC vehicle, amiodarone (IV or IPC) or dl-sotalol (IV or IPC). Epicardial and endocardial atrial effective refractory period and atrial response to burst pacing (rapid atrial response, RAR) were assessed before and after 3 hours of drug infusion at 2 mg.kg.h. IPC delivery produced steeply decreasing drug concentrations from epicardium to endocardium in both atria and ventricles. Plasma drug concentrations were significantly lower in IPC than in IV groups. IPC amiodarone and sotalol reduced epicardial RAR inducibility (-74% +/- 20% and -66% +/- 30%, respectively) compared with IV delivery (-11% +/- 17% and -17% +/- 28%, respectively; P < 0.05). Endocardial RAR inducibility was only reduced in the IPC amiodarone group (-70% +/- 17%, P < 0.05). In conclusion, IPC delivery of amiodarone and sotalol increases atrial drug concentration and antiarrhythmic effects at reduced plasma drug concentrations. These potential benefits are particularly prominent for IPC delivered amiodarone.

Comparison of electropharmacological effects of bepridil and sotalol in halothane-anesthetized dogs.

BACKGROUND: Bepridil is known to have a multiple ion channel-blocking property in the heart, which has been applied for the treatment of atrial fibrillation and drug-refractory ventricular tachyarrhythmias. In this study, the electro-pharmacological effects of bepridil were compared with those of dl-sotalol, a representative class III antiarrhythmic drug, using the halothane-anesthetized canine model. METHODS AND RESULTS: Cardiovascular and electrophysiological variables were measured under the halothane anesthesia. Intravenous administration of bepridil (0.3 mg/kg, n=4) delayed the intraventricular conduction and prolonged the ventricular effective refractory period, whereas dl-sotalol (0.3 mg/kg, iv, n=4) inhibited atrioventricular conduction and prolonged the atrial and ventricular effective refractory period. The additional administration of 10 times the higher dose of bepridil or dl-sotalol (ie, 3 mg/kg, iv, n=4 for each group) decreased blood pressure, suppressed ventricular contraction and sinus automaticity, and prolonged the atrial and ventricular effective refractory period and monophasic action potential duration, in addition to the effects of the low dose. CONCLUSIONS: The electropharmacological effects of bepridil and dl-sotalol were similar, although their potency for each cardiovascular variable varied significantly. These findings can be useful when selecting these drugs according to the pathophysiological condition of a patient.

Bifocal versus unifocal right atrial pacing under plasma level controlled sotalol to prevent atrial fibrillation in patients with symptomatic sinus bradycardia and paroxysmal atrial fibrillation.

AIMS: Bifocal right atrial pacing (BP) has been reported to increase arrhythmia-free intervals in patients with paroxysmal atrial fibrillation (PAF) under antiarrhythmic drugs. This study compares AF burden with unifocal pacing (UP) vs BP under sotalol. METHODS: In 19 patients with PAF a DDDR pacemaker with right atrial lateral and CS ostial leads was implanted. Sotalol was initiated. After a 3 month back-up pacing period patients were randomized to continuous UP or BP for 3 months and crossed over for 3 more months. Primary endpoint was AF burden. Secondary endpoints included number of episodes, time to first recurrence and safety of BP. RESULTS: The intention to treat analysis revealed 12.4% AF during back-up, 6.2% during UP and BP (p=0.91 UP vs BP, p=0.08 back-up vs UP and p=0.07 back-up vs BP). Per protocol analysis showed no advantage of either pacing mode (UP 4.8% and BP 5.4% AF, p=0.64). Overdrive pacing reduced AF burden to 6.2 vs 8.8% during back-up (p=0.09). Septal lead dislodgement occurred in 3 patients. CONCLUSION: Atrial pacing tends to reduce AF burden in patients with PAF under sotalol. An incremental effect of BP vs UP cannot be confirmed. BP may be complicated by elevated lead dislodgement rates.

Simultaneous determination of ten antiarrhythic drugs and a metabolite in human plasma by liquid chromatography--tandem mass spectrometry.

A simple, accurate and selective LC-MS/MS method was developed and validated for simultaneous quantification of ten antiarrhythic drugs (diltiazem, amiodarone, mexiletine, propranolol, sotalol, verapamil, bisoprolol, metoprolol, atenolol, carvedilol) and a metabolite (norverapamil) in human plasma. Plasma samples were simply pretreated with acetonitrile for deproteinization. Chromatographic separation was performed on a Capcell C(18) column (50mmx2.0mm, 5microm) using a gradient mixture of acetonitrile and water (both containing 0.02% formic acid) as a mobile phase at flow rate of 0.3ml/min. The analytes were protonated in the positive electrospray ionization (ESI) interface and detected in multiple reaction monitoring (MRM) mode. Calibration curves were linear over wide ranges from sub- to over-therapeutic concentration in plasma for all analytes. Intra- and inter-batch precision of analysis was <12.0%, accuracy ranged from 90% to 110%, average recovery from 85.0% to 99.7%. The validated method was successfully applied to therapeutic drug monitoring (TDM) of antiarrhythic drugs in routine clinical practice.

Development an ion-pair liquid chromatographic method for determination of sotalol in plasma using a monolithic column.

A rapid and sensitive ion-pair HPLC method using a monolithic column and fluorescence detection has been developed for quantification of sotalol in plasma. The assay enables the measurement of sotalol for therapeutic drug monitoring with a minimum quantification limit of 10 ng ml(-1). The analytical method involves simple, one-step protein precipitation and no extraction procedure is needed. Sample preparation is fast and the analytical recovery was complete. The separation was carried out in reversed-phase conditions using a Chromolith Performance (RP-18e, 100 mm x 4.6 mm) column at ambient temperature. The mobile phase was 10% acetonitrile, 0.001 M heptane sulfonic acid, 0.02 M sodium dihydrogen phosphate, and distilled water to 100%, adjusted to pH 5.5 at a flow rate of 1.8 ml/min. The excitation wavelength was set at 235 nm, emission at 300 nm. The calibration curve was linear over the concentration range 20-1500 ng ml(-1). The coefficients of variation for inter-day and intra-day assay were found to be less than 7%. The method has been applied to the determination of sotalol in plasma from 12 subjects dosed with racemic sotalol.

A micromethod for the quantification of atenolol in plasma using high-performance liquid chromatography with fluorescence detection: therapeutic drug monitoring of two patients with severe coronary insufficiency before cardiac surgery.

A simple, rapid, selective, and sensitive analytical method was developed for the quantification of atenolol in small volumes of plasma, by high-performance liquid chromatography with fluorescence detection. Only 200 microL of plasma was used for chromatographic analysis. Separation was performed on a C18 reverse-phase column (4 microm) using a binary mobile phase consisting of 0.05 M of phosphate buffer, pH 5.5, and methanol (80:20, vol/vol) at a flow rate of 0.7 mL/minute. The retention times of atenolol and of the internal standard (sotalol) were 12.7 and 10.4 minutes, respectively. Validation of this analytical method showed a good linear correlation (8-2000 ng/mL), high sensitivity (quantification limit: 8 ng/ml and detection limit: 4 ng/mL), accuracy of 99.3%, and intraday and interday precision of 5.3% and 6.9%, respectively. Absolute recovery was 93.7%. The method was found to be robust, with acceptable stability. The analytical method was validated by the quantification of atenolol in plasma obtained from 2 patients with unstable angina, scheduled for myocardium revascularization surgery, who were chronically treated with 50 mg of atenolol administered per os once a day. The method developed was found to be adequate for use in pharmacokinetic studies and in adjusted dose pharmacotherapy.

Development of an intravenous microdialysis method for pharmacokinetic investigations in humans.

INTRODUCTION: Limited blood volume is a major problem in pharmacokinetic investigations in specific populations, e.g. children. Intravenous microdialysis might help to obtain improved data sets as it is already successfully done in small animals. Since quantification of drugs is crucial in microdialysis, we developed an in vitro method to produce a workable intravenous microdialysis for human use. METHODS: A specifically designed microdialysis cell consisting of glass was heated to 37 degrees C. The cell was filled with Ringer's solution, plasma or whole blood. A microdialysis probe was inserted into the cell and perfused with Ringer's solution with addition of 4% dextran. The beta-receptor blocker sotalol served as a test drug. The stepwise in vitro evaluation process addressed issues of loss of dialysate, calibration by retrodialysis and relative recovery. These conditions were then applied in an in vivo pilot study to one single healthy volunteer after written informed consent. RESULTS: To address loss of perfusion fluid 4% of dextran was added and high and constant amounts of dialysate were achieved. To account for changes in the relative recovery a continuous use of retrodialysis by the calibrator atenolol was introduced. The recovery of atenolol was comparable to sotalol. The pharmacokinetic analysis revealed that sotalol concentrations from microdialysates were not different from conventional plasma samples (100+/-11%, n=33) resulting in subsequent comparable pharmacokinetic parameters. DISCUSSION: This stepwise approach using an in vitro device enabled us to demonstrate the determination of pharmacokinetic parameters of sotalol. The most important evaluation step is represented by the continuous use of retrodialysis by the calibrator atenolol because it can account for changes in the relative recovery of the drug. This approach should be a starting point to simplify pharmacokinetic studies in special populations, e.g. in small children, to improve drug treatment.

Liquid-phase microextraction based on carrier mediated transport combined with liquid chromatography-mass spectrometry. New concept for the determination of polar drugs in a single drop of human plasma.

Recently, we demonstrated for the first time liquid-phase microextraction (LPME) of polar drugs based on carrier mediated transport. In this new extraction technique, selected analytes were extracted as ion-pairs from small volumes of biological samples, through a thin layer of a water immiscible organic solvent immobilised in the pores of a porous hollow fibre (liquid membrane), and into a microl volume of an acidic aqueous acceptor solution placed inside the lumen of the hollow fibre. In the current paper, this new extraction technique was combined with liquid chromatography-mass spectrometry (LC-MS) for the first time. Carrier mediated LPME was evaluated for several new model drugs (0.01