Sotalol. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use

HPLC and LC-MS/MS-Based Quantitative Characterization of Related Substances Associated with Sotalol Hydrochloride

In total, three related substances (RS) associated with sotalol hydrochloride (STHCl) were herein identified with a novel gradient high-performance liquid chromatography (HPLC) protocol. Further characterization of these substances was then performed via liquid chromatography-mass spectroscopy (LC-MS/MS) and nuclear magnetic resonance (NMR) approaches. For these analyses, commercial STHCl samples were used for quantitative HPLC studies and the degradation of STHCl under acidic (1M HCl), alkaline (1M NaOH), oxidative (30% H2O2), photolytic (4500 Lx), and thermal stress conditions (100 °C) was assessed. This approach revealed this drug to be resistant to acidic, alkaline, and high-temperature conditions, whereas it was susceptible to light and oxidation as confirmed through long-term experiments. The putative mechanisms governing RS formation were also explored, revealing that RS3 was derived from the manufacturing process, whereas RS2 was generated via oxidation and RS1 was generated in response to light exposure. The cytotoxicity of these RS compounds was then assessed using MTT assays and acute toxicity test. Overall, this study provides details regarding the characterization, isolation, quantification, and toxicological evaluation of STHCl and associated RS compounds together with details regarding the precise, specific, and reliable novel HPLC technique, thus providing the requisite information necessary to ensure STHCl purity and safety.

Chemical Exposure Highlighted without Any A Priori Information in an Epidemiological Study by Metabolomic FT-ICR-MS Fingerprinting at High Throughput and High Resolution

Epidemiological studies aim to assess associations between diseases and risk factors. Such investigations involve a large sample size and require powerful analytical methods to measure the effects of risk factors, resulting in a long analysis time. In this study, chemical exposure markers were detected as the main variables strongly affecting two components coming from a principal component analysis (PCA) exploration of the metabolomic data generated from urinary samples collected on a cohort of about 500 individuals using direct introduction coupled with a Fourier-transform ion cyclotron resonance instrument. The assignment of their chemical identity was first achieved based on their isotopic fine structures detected at very high resolution (Rp > 900,000). Their identification as dimethylbiguanide and sotalol was obtained at level 1, thanks to the available authentic chemical standards, tandem mass spectrometry (MS/MS) experiments, and collision cross section measurements. Epidemiological data confirmed that the subjects discriminated by PCA had declared to be prescribed these drugs for either type II diabetes or cardiac arrhythmia. Concentrations of these drugs in urine samples of interest were also estimated by rapid quantification using an external standard calibration method, direct introduction, and MS/MS experiments. Regression analyses showed a good correlation between the estimated drug concentrations and the scores of individuals distributed on these specific PCs. The detection of these chemical exposure markers proved the potential of the proposed high-throughput approach without any prior drug exposure knowledge as a powerful emerging tool for rapid and large-scale phenotyping of subjects enrolled in epidemiological studies to rapidly characterize the chemical exposome and adherence to medical prescriptions.

Why translation from basic discoveries to clinical applications is so difficult for atrial fibrillation and possible approaches to improving it

Atrial fibrillation (AF) is the most common sustained clinical arrhythmia, with a lifetime incidence of up to 37%, and is a major contributor to population morbidity and mortality. Important components of AF management include control of cardiac rhythm, rate, and thromboembolic risk. In this narrative review article, we focus on rhythm-control therapy. The available therapies for cardiac rhythm control include antiarrhythmic drugs and catheter-based ablation procedures; both of these are presently neither optimally effective nor safe. In order to develop improved treatment options, it is necessary to use preclinical models, both to identify novel mechanism-based therapeutic targets and to test the effects of putative therapies before initiating clinical trials. Extensive research over the past 30 years has provided many insights into AF mechanisms that can be used to design new rhythm-maintenance approaches. However, it has proven very difficult to translate these mechanistic discoveries into clinically applicable safe and effective new therapies. The aim of this article is to explore the challenges that underlie this phenomenon. We begin by considering the basic problem of AF, including its clinical importance, the current therapeutic landscape, the drug development pipeline, and the notion of upstream therapy. We then discuss the currently available preclinical models of AF and their limitations, and move on to regulatory hurdles and considerations and then review industry concerns and strategies. Finally, we evaluate potential paths forward, attempting to derive insights from the developmental history of currently used approaches and suggesting possible paths for the future. While the introduction of successful conceptually innovative new treatments for AF control is proving extremely difficult, one significant breakthrough is likely to revolutionize both AF management and the therapeutic development landscape.

Machine read frontal QRS-T angle and QTc is no substitute for manual measurement of QTc in pro-arrhythmic drug overdose

INTRODUCTION

To investigate whether there is an association between the blocking of cardiac potassium channels, which is characterised by a prolonged QTc interval and the frontal QRS-T angle after overdose by QT prolonging drugs.

METHODS

We obtained patient medical records associated with QT prolonging drugs from 3 different hospitals: the Calvary Mater Newcastle Hospital (CMNH), Royal Prince Alfred Hospital (RPAH) and Prince of Wales Hospital (POWH). RPAH and POWH admissions were taken between 4/01/2017 to 1/11/2019, and CMNH admissions were taken between 4/01/2013 to 24/06/2018. Demographic information and details of overdose were collected. All admission ECGs were manually measured. Linear regression was used to assess the relationship between various QTc formulas and the frontal QRS-T angle. A Bland-Altman plot was used to examine agreement between manual and machine QT intervals.

RESULTS

144 patients met the inclusion criteria for analysis. None of the patients developed torsades de pointes (TdP). There was no linear association between the QRS-T angle and the various QTc formulas (For QRS-T angle: QTcRTH: p = 0.76, QTcB: p = 0.83, QTcFri: p = 0.90, QTcFra: p = 0.13, QTcH: p = 0.97; For square root transformation of the QRS-T angle: QTcRTH: p = 0.18, QTcB: p = 0.33, QTcFri: p = 0.95, QTcFra: p = 0.47, QTcH: p = 0.33). Agreement between machine and manual QT measurements was low.

CONCLUSIONS

The frontal QRS-T angle cannot substitute the QTc in assessing the blockage of cardiac potassium channels in drug induced long QT syndrome. We also support the consensus that despite the availability of machine measurements of the QT interval, manual measurements should also be performed.

Single and mixture toxicity of four pharmaceuticals of environmental concern to aquatic organisms, including a behavioral assessment

Pharmaceuticals are frequently detected in aquatic environments as mixtures and can cause toxic effects to non-target organisms. We aimed to evaluate the single and mixture effects of the pharmaceuticals metformin, bisoprolol, ranitidine and sotalol using Daphnia similis and Danio rerio. In addition, we aimed to test the predictive accuracy of the mathematical models concentration addition and independent action and to evaluate the nature of the possible toxicological interactions among these pharmaceuticals using the combination index-isobologram model. The acute toxicity of these four pharmaceuticals individually and of their binary mixtures were evaluated using the D. similis tests. Developmental and behavioral effects induced by the pharmaceuticals in quaternary mixtures were evaluated using D. rerio embryos. We observed that most of the binary mixture effects were in the zone between the effects predicted by the concentration addition and the independent action model. The combination index-isobologram model showed to be adequate to describe the nature of possible interactions occurring between the combined pharmaceuticals. Developmental and behavioral acute adverse effects seem not to be induced by the joint action of the quaternary mixture of the evaluated pharmaceuticals on D. rerio embryos, at the concentrations at which they are usually found in surface fresh waters. However, from the results obtained with D. similis, we can conclude that assessing the ecological risk based on the effects of individual pharmaceuticals can underestimate the risk level posed by these environmental contaminants.

Design, Synthesis and Antitumor Activity of Novel link-bridge and B-Ring Modified Combretastatin A-4 (CA-4) Analogues as Potent Antitubulin Agents

A series of 12 novel acylhydrazone, chalcone and amide–bridged analogues of combretastatin A-4 were designed and synthesized toward tubulin. All these compounds were determined by elemental analysis, ¹H NMR, and MS. Among them, compound 7 with acylhydrazone-bridge, bearing a benzyl at the indole-N position, was identified as a potent antiproliferative agent against a panel of cancer cell lines with IC₅₀ values ranging from 0.08 to 35.6 μM. In contrast, its cytotoxic effects on three normal human cells were minimal. Cellular studies have revealed that the induction of apoptosis by compound 7 was associated with a collapse of mitochondrial membrane potential, accumulation of reactive oxygen species, alterations in the expression of some cell cycle-related proteins (Cyclin B1, Cdc25c, Cdc2, P21) and some apoptosis-related proteins (Bax, PARP, Bcl-2, Caspase3). The docking mode showed the binding posture of CA-4 and compound 7 are similar in the colchicine-binding pocket of tubulin, as confirmed by colchicine-tubulin competitive binding assay, tubulin polymerization inhibitory activity, extracellular protein expression determination assay and confocal immunofluorescence microscopy. In vivo study, compound 7 effectively inhibited A549 xenograft tumor growth without causing significant loss of body weight suggesting that compound 7 is a promising new antimitotic agent with clinical potential.

Antiarrhythmics: elimination and dosage considerations in hepatic impairment

Many drugs, including most antiarrhythmics (some of which are now of limited clinical use) are eliminated by the hepatic route. If liver function is impaired, it can be anticipated that hepatic clearance will be delayed, which can lead to more pronounced drug accumulation with multiple dosing. Consequently, the potential risks of adverse events could be increased, especially as antiarrhythmics have a narrow therapeutic index. The present review summarises the available pharmacokinetic data on the most popular antiarrhythmic drugs to identify the enzymes involved in the metabolism of the various agents and confirm whether liver disease affects their elimination. Despite long usage of some of these drugs (e.g. amiodarone, diltiazem, disopyramide, procainamide and quinidine), surprisingly few data are available in patients with liver disease, making it difficult to give recommendations for dosage adjustment. In contrast, for carvedilol, lidocaine (lignocaine), propafenone and verapamil, sufficient clinical studies have been performed. For these drugs, a marked decrease in systemic and/or oral clearance and significant prolongation of the elimination half-life have been documented, which should be counteracted by a 2- to 3-fold reduction of the dosage in patients with moderate to severe liver cirrhosis. For sotalol, disopyramide and procainamide, renal clearance contributes considerably to overall elimination, suggesting that dosage reductions are probably unnecessary in patients with liver disease as long as renal function is normal. The hepatically eliminated antiarrhythmics are metabolised mainly by different cytochrome P450 (CYP) isoenzymes (e.g. CYP3A4, CYP1A2, CYP2C9, CYP2D6) and partly also by conjugations. As the extent of impairment in clearance is in the same range for all of these agents, it could be assumed that they have a common vulnerability and that, consequently, hepatic dysfunction will affect CYP-mediated phase I pathways in a similar fashion. The severity of liver disease has been estimated clinically by the validated Pugh score, and functionally by calculation of the clearance of probe drugs (e.g. antipyrine). Both approaches can be helpful in estimating/predicting impairments in drug metabolism, including antiarrhythmics. In conclusion, hepatic impairment decreases the elimination of many antiarrhythmics to such an extent that dosage reductions are highly recommended in such populations, especially in patients with cirrhosis.

Therapeutic drug monitoring of antiarrhythmic drugs

Most antiarrhythmic drugs fulfil the formal requirements for rational use of therapeutic drug monitoring, as they show highly variable plasma concentration profiles at a given dose and a direct concentration-effect relationship. Therapeutic ranges for antiarrhythmic drugs are, however, often very poorly defined. Effective drug concentrations are based on small studies or studies not designed to establish a therapeutic range, with varying dosage regimens and unstandardised sampling procedures. There are large numbers of nonresponders and considerable overlap between therapeutic and toxic concentrations. Furthermore, no study has ever shown that therapeutic drug monitoring makes a significant difference in clinical outcome. Therapeutic concentration ranges for antiarrhythmic drugs as they exist today can give an overall impression about the drug concentrations required in the majority of patients. They may also be helpful for dosage adjustment in patients with renal or hepatic failure or in patients with possible toxicological or compliance problems. Their use in optimising individual antiarrhythmic therapy, however, is very limited.

Beta-adrenergic blockers in systemic hypertension: pharmacokinetic considerations related to the current guidelines

Beta-adrenergic blockade has provided one of the major pharmacotherapeutic advances of the 20th century. Beta-blockers are first-line drugs for the management of systemic hypertension, used alone and in combination with other antihypertensive agents. Drugs in the beta-blocking class have the common property of blocking the binding of catecholamines to beta-adrenergic receptor sites; however, there are significant pharmacodynamic and pharmacokinetic differences between the individual agents that are of clinical importance. Among these differences are the completeness of gastrointestinal absorption, the degree of hepatic first-pass metabolism, lipid solubility, protein binding, brain penetration, concentration within the cardiac tissue, rate of hepatic biotransformation, and renal clearance of drug and/or metabolites. Long-acting formulations of existing beta-blockers are currently in use, and ultra-short-acting agents are also available. Age, race, cigarette smoking and concomitant drug therapy can also influence the pharmacokinetics of beta-blocking drugs. The wide interpatient variability in plasma drug concentrations observed with beta-blockers makes this parameter unreliable in routine patient management. Despite the pharmacokinetic differences among beta-blockers, these drugs should always be titrated to achieve the desired individual patient response.

Enantioselective determination of (R)- and (S)-sotalol in human plasma by on-line coupling of a restricted-access material precolumn to a cellobiohydrolase I-based chiral stationary phase

A liquid chromatographic column-switching method for the enantioselective determination of (RS)-sotalol in plasma was developed and validated. The method is based on the on-line coupling of a precolumn filled with the restricted access material LiChrospher ADS to a cellobiohydrolase I-based chiral stationary phase (CSP). The plasma samples were injected onto the precolumn using a mobile phase containing 1% methanol in 10 mM phosphate buffer at pH 7.4 for 10 min for the removal of matrix components. The analytes were transferred to the CSP for their enantiomeric separation by backflushing the precolumn with 15% 2-propanol in 10 mM phosphate buffer (pH 7.0) including 0.05 mM EDTA. The quantitative determination of the sotalol enantiomers was possible upon addition of the internal standard (S)-atenolol. The method was validated showing a good linearity in the concentration range from 25 to 1000 microg l(-1) for each enantiomer. The average values of the intra- and inter-day variability were 1.17% and 3.42%, respectively, for (R)-sotalol and 1.24% and 1.99%, respectively, for (S)-sotalol. The applicability of the method to real world samples has been proven by means of two pharmacokinetic studies. They revealed that the pharmacokinetic properties of the sotalol enantiomers do not differ significantly neither for healthy young volunteers after single dose application nor for elder patients in the steady state.

Adverse dermatologic effects of cardiovascular drug therapy: part I

Cardiovascular disease is common, affecting an increasing number of persons as the population ages. To combat this growing health problem, physicians use a multitude of medications in the treatment of their patients. Although pharmacologic therapy greatly enhances quality of life for a majority of patients, there is always the potential for an unfavorable reaction. For example, cardiovascular drugs can induce a vast array of adverse dermatologic responses. This article reviews the various cutaneous reaction patterns that can occur as a result of treatment with Class I and II antiarrhythmic agents.

Initial orthostatic hypotension as a cause of recurrent syncope: a case report

A 60-year-old male patient with recurrent unexplained syncope on standing was studied. During continuous, noninvasive blood pressure (BP) recording with a Finapres device, an abnormally large and symptomatic initial decrease in systemic BP was documented. After 2 minutes of standing, BP had recovered. The transient decrease in BP was attributed to the use of a combination of antidepressants known to interfere with sympathetic function. This case shows the importance of continuous, noninvasive BP measurement on standing: routine intermittent BP recording would have missed the abnormality. In patients using medications such as antidepressants, initial transient hypotension should be considered as the cause of falls and syncope.

Temperature-induced inversion of elution order in the enantioseparation of sotalol on a cellobiohydrolase I-based stationary phase

The effect of temperature on the resolution of (RS)-sotalol by immobilized cellobiohydrolase I (CBH I) was studied between 5 and 40 degrees C and Van 't Hoff plots of ln k versus 1/T were acquired at different pH values of the aqueous mobile phase and in the presence of varying organic cosolvents. The elution order of the enantiomers reverses in the range between 17 and 28 degrees C. Beyond this range, enantioseparations with comparatively high resolution factors are achieved either by decreasing or by increasing the temperature. The composition of the mobile phase influences the "crossover" temperature as well as the character of the global adsorption process of the (R)-(-)-enantiomer. Under certain conditions, (R)-(-)-sotalol exhibits an unusual endothermic adsorption behavior. Its retention time increases with increasing temperature. At room temperature (23 degrees C) the enantiomeric elution order can also be regulated by the solvent additive.

Sotalol: Current Status and Expanding Indications

BACKGROUND: The role of antiarrhythmic drug therapy continues to undergo major changes. The change is necessitated by the advent of invasive interventional procedures, such as catheter ablation of arrhythmias and the use of implantable devices for sensing and terminating life-threatening ventricular arrhythmias and symptomatically traublesome supraventricular arrhythmias. Many conventional and time-honored drugs, such as sodium channel blockers, have been found either to be ineffective or to have the potential to produce serious proarrhythmic reactions. Attention is therefore focused on compounds that prolong repolarization and reduce sympathetic stimulation. Two compounds, amiodarone and sotalol, have emerged as prototypes of drugs of the future. METHODS AND RESULTS: This review focuses on sotalol for controlling supraventricular and ventricular tachyarrhythmias. Sotalol is a major antiarrhythmic agent that combines potent class III action with nonselective beta-blocking properties. The drug's pharmacokinetics is simple. Its elimination half-life is 10-15 hours, the drug being excreted almost exclusively by the kidneys. Sotalol's pharmacokinetics allows development of optimal dosing for initiation of therapy relative to changes in creatinine clearance with further dose adjustment by monitoring the QT interval on the surface electrocardiogram. The compound exerts broad-spectrum antiarrhythmic actions in supraventricular and ventricular arrhythmias. It prevents inducible ventricular tachycardia (VT) and ventricular fibrillation (VF) in approximately 30% of patients with a higher figure for the suppression of spontaneously occurring arrhythmias documented on Holter recordings. CONCLUSIONS: The major role of sotalol is in the management of VT/VF often in conjunction with an implantable cardioverter/defibrillator, in which context it lowere the defibrillation threshold. Sotalol is superior to class I agents, especially in VT/VF and in survivors of cardiac arrest. Sotalol has emerged as a major antifibrillatory compound for the control of life-threatening ventricular arrhythmias as the main indication. Data have indicated its potential for the maintenance of stability of sinus rhythm in patients with atrial fibrillation and flutter after electrical conversion and in preventing their occurrence in a variety of clinical settings.

Importance of beta blockade in the therapy of serious ventricular arrhythmias

Beta blockers have traditionally been considered relatively poor antiarrhythmic agents for patients with ventricular arrhythmias. This view is based on the observations that beta blockers are less effective in suppressing spontaneous ventricular ectopy or inducible ventricular arrhythmias than are the class I and class III agents. However, there are convincing data that beta blockers can have a clinically important antiarrhythmic effect and prevent arrhythmic and sudden death. Beta blockers have multiple potential effects that can contribute to a therapeutic antiarrhythmic action, including an antiadrenergic/vagomimetic effect, a decrease in ventricular fibrillation threshold, and prevention of a catecholamine reversal of concomitant class I/III antiarrhythmic drug effects. Postinfarction trials, recent congestive heart failure studies, and observations in patients who are at risk for sustained ventricular arrhythmias all suggest a potent antiarrhythmic effect of beta blockade.

Combination of sotalol and quinidine in a canine model of torsades de pointes: no increase in the QT-related proarrhythmic action of sotalol

INTRODUCTION

Clinical treatment with a combination of Class IA and III antiarrhythmic drugs is not recommended, as they both favor bradycardia-dependent proarrhythmic events such as torsades de pointes (TdP). However, this theoretical additive effect on ventricular repolarization has never been demonstrated and could be questioned as other Class I drugs, such as mexiletine, a Class IB drug, limit the number of sotalol-induced TdP in dogs with AV block, suggesting the possibility of an antagonistic action of Class I properties against Class III effects.

METHODS AND RESULTS

We compared the electrophysiologic and proarrhythmic effects of sotalol (Class III) alone and combined with quinidine (Class IA) in a canine model of acquired long QT syndrome. Seven hypokalemic (K+: 3 +/- 0.1 mEq/L) dogs with chronic AV block had a demand pacemaker implanted and set at a rate of 25 beats/min. They were submitted to two (sotalol-alone and sotalol-plus-quinidine) experiments 48 hours apart using a randomized cross-over protocol. They were pretreated with quinidine (10 mg/kg + 1.8 mg/kg per hour) or saline infused throughout the experiment, and given sotalol (4.5 mg/kg + 1.5 mg/kg per hour) for 2 hours, 30 minutes after the beginning of the pretreatment infusion during both experiments. Ventricular and atrial cycle lengths were similarly increased by sotalol after quinidine or saline. The sotalol-induced prolongation of the QT interval was significantly shorter in quinidine-pretreated dogs (24 +/- 7 msec after quinidine vs 40 +/- 8 msec after saline). Fewer dogs developed TdP: significantly during the first hour of infusion (1/7 sotalol-plus-quinidine vs 6/7 sotalol-alone dogs, P < 0.05) but nonsignificantly during the second hour (3/7 vs 6/7).

CONCLUSION

In this model, the sotalol-plus-quinidine combination is at least no more arrhythmogenic than either of the drugs given alone.

Influence of cimetidine coadministration on the pharmacokinetics of sotalol enantiomers in an anaesthetized rat model: evidence supporting active renal excretion of sotalol

Sotalol (STL) is an amphoteric, chiral beta-adrenergic blocking drug useful in the treatment of both hypertension and ventricular arrhythmias. In the human and rat, STL enantiomers are predominantly cleared from the body by the kidney as intact drug. The renal clearance (Clr) of STL enantiomers substantially exceeds the glomerular filtration rate (GFR) in the human and rat. In this report, the hypothesis that STL enantiomers are excreted by an active renal transport system was investigated in the rat by coadministering racemic STL (10 mg kg-1) with cimetidine, an inhibitor of renal tubular secretion of organic cations. To compare the effects of short-term and sustained cimetidine exposure on STL enantiomer disposition, cimetidine was administered either as a single bolus (30 mg kg-1, n = 7) immediately prior to the STL dose, or as a 30 mg kg-1 bolus plus a 50 mg kg-1 infusion over the 6 h study period (n = 7). Blood and urine samples were collected over 6 h, during which time anaesthesia was maintained via intraperitoneal administration of pentobarbital. Cimetidine bolus and cimetidine infusion reduced STL enantiomer Clr by 43 and 59%, respectively, compared with respective saline controls. Significant stereoselectivity was observed in the cimetidine infusion group: systemic clearance, Clr (R > S), and AUC (S > R), although the magnitude of stereoselectivity was less than 5%. This study supports the hypothesis that STL enantiomers are predominantly cleared from the rat via a renal cationic transport mechanism and that this system can be competitively inhibited by the presence of cimetidine.

Electrophysiologic Effects of Beta-blocking Agent, Tilisolol, on Isolated Guinea Pig Ventricular Myocytes

BACKGROUND: Electrophysiologic effects of a beta-blocking agent, tilisolol, were studied with isolated guinea pig ventricular myocytes using the whole cell patch clamp technique. METHODS AND RESULTS: Tilisolol at 10 µM or higher concentrations prolonged action potential duration (APD) at 90% repolarization (APD(90)) and at 100 µM or higher concentrations shortened APD at 20% repolarization (APD(20)) without changes in resting membrane potential. At 10 µM concentration tilisolol prolonged APD(90) from 236.6 +/- 55.3 ms in the control to 253.4 +/- 52.4 ms (n = 16; P <.01), while APD(20) was unaffected. At 100 µM tilisolol, APD(20) was shortened from 143.6 +/- 15.7 ms in the control to 133.7 +/- 22.6 ms (n = 8; P <.05). Under voltage clamp, tilisolol decreased the delayed rectifier K(+) current (I(K1)). Applications of 10 µM and 100 µM tilisolol reduced the maximal conductance of I(K) by 35.7 +/- 3.5% and 47.4 +/- 3.5% of the control, respectively, without changes in voltage dependence (n = 10). Tilisolol at 100 µM decreased the L-type Ca(2+) current (I(Ca.L)) by 22.0 +/- 9.8% (n = 6) of the control, and the inactivation curve was shifted to a hyperpolarizing direction. CONCLUSIONS: Tilisolol has a direct membrane action to depress I(K) and I(Ca.L), in addition to its beta-receptor blocking action.

Enantioselective determination of sotalol enantiomers in biological fluids using high-performance liquid chromatography

A simple and sensitive high-performance liquid chromatographic (HPLC) method for the determination of (+)-(S)-sotalol and (-)-(R)-sotalol in biological fluids was established. Following extraction with isopropyl alcohol from biological samples on a Sep-Pak C18 cartridge, the eluent was derivatized with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate (GITC). The diastereoisomeric derivates were resolved by HPLC with UV detection at 225 nm. Calibration was linear from 0.022 to 4.41 micrograms/ml in human plasma and from 0.22 to 88.2 micrograms/ml in human urine for both (+)-(S)- and (-)-(R)-sotalol. The lower limit of determination was 0.022 microgram/ml for plasma and 0.22 microgram/ml for urine. The within-day and day-to-day coefficients of variation were less than 7.5% for each enantiomer at 0.09 and 1.8 microgram/ml in plasma and at 0.44 and 4.4 micrograms/ml in urine. The method is also applicable to other biological specimens such as rat, mouse and rabbit plasma.

Newer developments in the management of atrial fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia encountered in clinical practice. Unlike reentrant supraventricular tachycardia and malignant ventricular tachyarrhythmias, for which highly effective and safe nonpharmacologic therapies are available, the treatment of AF remains controversial and often problematic. Whereas electrical cardioversion restores sinus rhythm in most patients with AF, the maintenance of sinus rhythm often requires membrane-active antiarrhythmic drugs that may increase mortality by inducing ventricular proarrhythmia. The control of ventricular response rate, often associated with oral anticoagulation to prevent thromboembolic complications, is an alternative strategy in AF management. The relative efficacy and risks of these strategies and their respective role in different patient subgroups remain to be established. This article focuses on newer developments in the management of AF, including prospects for improved methods to maintain sinus rhythm, newer approaches to rate control, controversies regarding the use of oral anticoagulation, and novel nonpharmacologic therapies. These newer developments may lead over the next 10 years to a revolution in the management of AF as profound as that produced over the last 10 years by nonpharmacologic therapy of other arrhythmias.

Mexiletine antagonizes effects of sotalol on QT interval duration and its proarrhythmic effects in a canine model of torsade de pointes

OBJECTIVES

The arrhythmogenic and electrophysiologic properties of sotalol, a class III antiarrhythmic drug, administered alone and in combination with mexiletine, a class I antiarrhythmic drug, were compared in conscious dogs predisposed to torsade de pointes arrhythmias.

BACKGROUND

The utility of sotalol is limited by proarrhythmia related to excessive delays in repolarization. The addition of mexiletine may limit the risk of torsade de pointes because it reduced in vitro the sotalol-induced increase in action potential duration.

METHODS

Two studies were performed in eight hypokalemic dogs (plasma potassium level < or = 3.2 mmol/liter) with chronic atrioventricular block (mean ventricular cycle length, RR 1,100 ms) at 3-day intervals using a crossover protocol. Intravenous sotalol (4.5 + 1.5 mg/kg body weight per h) alone was given for 2 h, or, on another day, an intravenous mexiletine infusion (4.5 + 1.5 mg/kg per h) was begun 30 min before sotalol infusion. Spontaneous ventricular cycle length and QT interval and ventricular effective refractory period at the 1,000-ms pacing cycle length were measured at baseline and 30 min after the onset of each drug infusion. The electrocardiogram (ECG) was continuously monitored for torsade de pointes.

RESULTS

Sotalol plus mexiletine and sotalol alone had a significant (p < or = 0.05) and similar effect on ventricular cycle length (+ 800 +/- 93 vs. + 690 +/- 104 ms [mean +/- SEM]) and ventricular effective refractory period (+ 20 +/- 4 vs. + 25 +/- 4 ms), but sotalol plus mexiletine had a lesser effect on QT interval (+ 20 +/- 6 vs. + 50 +/- 8 ms, p < or = 0.05). Torsade de pointes is less frequent (one of eight dogs vs. six of eight dogs, p = 0.02) with sotalol plus mexiletine than with sotalol alone.

CONCLUSIONS

The coadministration of a class Ib agent can reduce the proarrhythmic potential of a class III drug in experimental animals predisposed to torsade de pointes arrhythmias and further suggests the clinical utility of such a strategy.

Long-term antiarrhythmic efficacy and safety of d-sotalol in patients with ventricular tachycardia and a low ejection fraction

Since in patients with ventricular tachycardia (VT) and compromised left ventricular function, antiarrhythmic therapy poses a particular problem, an open-label safety study of d-sotalol, a new class III antiarrhythmic agent, was performed. Thirteen patients with defined VT and a low left ventricular ejection fraction (LVEF) were treated with orally administered d-sotalol, 100 mg bid, and in a few patients 100 mg tid, in an open study. Patients were followed up for 35 +/- 11 months, with the longest follow-up amounting to 51 months. The data obtained suggest that d-sotalol was moderately effective as an antiarrhythmic agent, in particular with respect to premature ventricular contractions (PVCs) and coupled and repetitive PVCs. The beneficial effect appeared to persist on long-term treatment. d-Sotalol was well tolerated and no subjective or objective adverse reactions were observed. There were no signs of worsening of congestive heart failure, proarrhythmogenic activity, or torsades de pointes, although QT-prolongation was observed. There were no dropouts in the study. Two patients died: One patient with idiopathic dilated cardiomyopathy (with LVEF = 11%) died suddenly after 38 months of follow-up and one patient after 17 months from recurrent myocardial infarction. Neither of these had shown recurrence of VT on 24 hour ambulatory ECG recordings. In conclusion, in this small group of patients d-sotalol appeared to be safe and well tolerated during long-term treatment of patients with VT and poor left ventricular function. There were clear suggestions of antiarrhythmic activity, reflected by the suppression of complex ventricular arrhythmias and by the absence of recurrent VT on long-term follow-up in the majority of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Multicenter trial of sotalol compared with procainamide in the suppression of inducible ventricular tachycardia: a double-blind, randomized parallel evaluation. Sotalol Multicenter Study Group

Sotalol is the prototype class III agent that combines beta-blocking properties with the propensity to prolong the effective refractory period by lengthening the action potential duration. Its precise effect on the prevention of ventricular tachycardia-ventricular fibrillation (VTVF) compared to class I agents has not been evaluated in a blinded study. In a double-blind parallel-design multicenter study, the electrophysiologic and antiarrhythmic effects of intravenous and oral sotalol (n = 55) and procainamide (n = 55) were therefore compared in patients with VTVF inducible by programmed electric stimulation. Sotalol produced a greater effect on lengthening the ventricular effective refractory period (VERP). It prevented the inducibility of VTVF in 30% versus 20% for procainamide, but this was not significantly different. In an alternate therapy group (n = 41) of similar patients previously refractory to or intolerant of procainamide, intravenous sotalol prevented inducibility in 32%. The pooled overall sotalol efficacy rate was 31%. There was a significant relation between the increase in the VERP and the prevention of inducibility of VTVF (n = 56; p < 0.02). VERP of > or = 300 msec was critical for the prevention of VTVF inducibility. Thirteen sotalol and 6 procainamide responders from the randomized group and 30 from the nonrandomized groups completed 1 year of oral sotalol therapy follow-up. Life-table analysis of these patient in each group showed a trend in favor of sotalol; however, statistical analysis was not possible because of the small numbers of patients. Both sotalol and procainamide were well tolerated. In the randomized group there was one case of sudden death during treatment with sotalol and two cases of nonfatal torsades de pointes in the procainamide group and two in the sotalol group; in the nonrandomized alternate therapy group, there were 6 cases of nonfatal torsades de pointes. The data support the emerging role of sotalol in the control of symptomatic ventricular tachycardia and fibrillation.

Adverse dermatologic reactions from antiarrhythmic drug therapy

Undesirable cutaneous reactions to drugs may occur early or late in the course of treatment. The ingestion of drugs may also aggravate existing dermatologic conditions. The adverse dermatologic reactions from antiarrhythmic drug therapy are reviewed. The exact incidence of dermatologic side effects from cardiovascular drugs has been difficult to estimate because of sporadic reporting. In this review, the cutaneous side effects are discussed according to drug class and the type of dermatologic reaction.

Stereospecific evaluation of sotalol pharmacokinetics in a rat model: evidence suggesting an enantiomeric interaction

Sotalol (STL) is a chiral beta-adrenergic blocking drug, which is useful clinically as the racemate in treating hypertension, and is also useful as a class III antiarrhythmic when administered as the pure S-enantiomer. Utilizing a stereospecific high-performance liquid chromatographic (HPLC) assay, the enantiomeric disposition of STL is reported after administration of racemate and both pure enantiomers to a rat model. After administration of the racemate, enantiomers of STL had similar plasma concentration-time profiles. Following administration of the pure S-enantiomer of STL, however, systemic clearance was significantly reduced; R-STL disposition after pure enantiomer administration was not significantly altered. Changes in systemic clearance of S-STL after either racemate or enantiomer dosing were explained by corresponding changes in renal clearance. Renal clearance values of S-STL were significantly reduced from 33.7 +/- 6.0 to 28.9 +/- 5.6 ml min-1 kg-1 for administration as racemate and pure enantiomer, respectively. As clearance of STL approximates reported values of renal blood flow, renal perfusion changes caused by the beta-blocking effects of R-STL may explain changes in S-STL disposition. It is suggested that dosing of STL as either racemate or pure enantiomer, depending on the clinical indication for use, may result in significantly altered enantiomer disposition.

Enantioselective bioanalysis of beta-blocking agents: focus on atenolol, betaxolol, carvedilol, metoprolol, pindolol, propranolol and sotalol

The recent developments in enantioselective HPLC-separation techniques are impressive and are driven by industrial and academic interests; thus there is for instance a high demand for developing stereoselective assays for chiral drugs in biological fluids. The beta-blocking agents, which possess an amino-propanol- or -ethanol side chain with at least one chiral centre, represent one of the most intensively investigated groups of more than 40 drugs introduced world wide. Seven of the most popular beta-blockers were chosen as representatives: atenolol; betaxolol; carvedilol; metoprolol; pindolol; propranolol; and sotalol, these span the whole range of lipophilicity to hydrophilicity (polarity). Enantioselective HPLC bioassays for these beta-blockers published so far, including techniques based on chiral derivatizing agents (CDAs), chiral stationary phases (CSPs) and chiral mobile phase additives (CMPAs) have been reviewed and documented in the light of general aspects together with pharmacokinetic and pharmacodynamic considerations.

Sotalol. An updated review of its pharmacological properties and therapeutic use in cardiac arrhythmias

Sotalol is a nonselective beta-adrenoceptor antagonist which prolongs cardiac repolarisation independently of its antiadrenergic action (class III antiarrhythmic properties). The antiarrhythmic action of sotalol appears to arise predominantly from its class III properties, and the drug exhibits a broader antiarrhythmic profile than the conventional beta-blockers. Sotalol is effective in controlling paroxysmal supraventricular tachycardias and the ventricular response to atrial fibrillation/flutter in Wolff-Parkinson-White syndrome, in maintaining sinus rhythm after cardioversion of atrial fibrillation/flutter, and in preventing initiation of supraventricular tachyarrhythmias following coronary artery bypass surgery. Sotalol shows promise in the control of nonmalignant and life-threatening ventricular arrhythmias, particularly those associated with ischaemic heart disease. It is effective in suppressing complex forms of ventricular ectopy, displaying superior antiectopic activity to propranolol and metoprolol. The acute efficacy of sotalol in preventing reinduction of sustained ventricular tachyarrhythmias and suppressing spontaneous episodes of these arrhythmias on Holter monitoring is translated into long term prophylactic efficacy against arrhythmia recurrence in approximately 55 to 85% of patients with refractory life-threatening ventricular arrhythmias. In addition, sotalol offers the advantage over the class I agents of reducing cardiac and all-cause mortality in the high risk population with life-threatening ventricular arrhythmias. The adverse effects of sotalol are primarily related to its beta-blocking activity and its class III property of prolonging cardiac repolarisation. Sotalol is devoid of overt cardiodepressant activity in patients with mild or moderate left ventricular dysfunction. The overall arrhythmogenic potential is moderately low, but torsade de pointes may develop in conjunction with excessive prolongation of the QT interval due to bradycardia, hypokalaemia or high plasma concentrations of the drug. In summary, sotalol displays a broad spectrum of antiarrhythmic activity, is haemodynamically well tolerated, and confers a relatively low proarrhythmic risk. It is likely to prove particularly appropriate in the treatment and prophylaxis of life-threatening ventricular tachyarrhythmias.

Pharmacologic basis of the antiarrhythmic and hemodynamic effects of sotalol

Sotalol is a competitive beta adrenoceptor antagonist devoid of membrane-stabilizing activity and intrinsic sympathomimetic activity that has no preferential actions on beta 1 or beta 2 responses. No other tested receptor systems are affected by sotalol. In addition to having class II (beta blockade) effects, sotalol also has class III antiarrhythmic activity. It increases the action potential duration (APD) and prolongs atrial and ventricular repolarization. The effect on APD is independent of beta blockade; the same effect is seen with similar concentrations of the d stereoisomer of sotalol, which does not have beta-blocking activity. Sotalol prolongs the rate-corrected QT interval and ventricular and atrial refractoriness without affecting atrial, His-Purkinje, or ventricular conduction velocity. Atrioventricular nodal conduction is decreased, largely because of beta blockade. Sotalol increases the fibrillation threshold and decreases the defibrillation threshold. Sotalol is an effective antiarrhythmic in various animal models of arrhythmia (e.g., chloroform, hydrocarbon-catecholamine, ouabain, and coronary ligation). In addition, it reduces the severity and frequency of arrhythmias induced by programmed electrical simulation. By comparison, metoprolol is ineffective and d-sotalol is as effective as the racemate in this model, indicating that this effect is independent of beta blockade. Sotalol causes concentration-dependent increases in the contractility of isolated ventricular tissue that is not blocked by previous beta or alpha blockade or catecholamine depletion. The positive inotropic effect may be related to inhibition of time-dependent K+ current responsible for the increase in APD. Like propranolol, sotalol decreases contractile force, heart rate, arterial blood pressure, left ventricular dP/dt, and cardiac output in intact animals due to blockade of circulating catecholamines. Sotalol consistently reduces the heart rate to a greater degree than propranolol and causes significantly less cardiac suppression than propranolol at a given heart rate.

Effect of oral sotalol on systemic hemodynamics and programmed electrical stimulation in patients with ventricular arrhythmias and structural heart disease

We explored the central hemodynamic responses to oral sotalol during dose titration in patients with ventricular arrhythmias who underwent programmed ventricular stimulation. Twelve patients were included in the study, 9 with a history of sustained ventricular tachyarrhythmias (6 postmyocardial infarction and 3 with cardiomyopathy) and 3 with a history of nonsustained ventricular tachycardia postmyocardial infarction. Left ventricular ejection fractions were < 45% in 10 patients, and < 35% in 5; the mean ejection fraction was 37% (range 20-51%). Sotalol prevented the induction of ventricular tachycardia in each of 3 patients with nonsustained ventricular tachycardia and in 6 of 9 with sustained ventricular tachycardia at baseline study. At peak action (2 hours) after sotalol loading (mean dose, 167 mg orally twice daily), the hemodynamic effects included bradycardia, decreased cardiac index, increased left ventricular filling pressure and systemic vascular resistance, and no change in stroke volume or stroke work index. One patient was not continued on sotalol, owing to an excessive increase in the pulmonary capillary wedge pressure, despite the lack of symptomatic heart failure. Congestive heart failure in association with marked bradycardia developed in another patient, who had suppression of inducible ventricular tachycardia after sotalol loading; this patient was managed with a reduction in the dose of sotalol and a regimen of digoxin and furosemide, and has been well compensated and without a recurrence of sustained ventricular tachycardia for more than 4 years. Ventricular tachycardia has been controlled with sotalol, without hemodynamic deterioration, in 6 of these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Sotalol: a novel beta-blocker with class III anti-arrhythmic activity

Initially synthesized in 1960, sotalol is a novel beta-adrenoreceptor blocking agent that also possesses class III anti-arrhythmic properties. The drug's ability to lengthen repolarization and prolong effective refractory periods in all cardiac tissues in addition to its beta-blocking effects make sotalol an attractive agent for use in a variety of supraventricular and ventricular arrhythmias.

Effects of central serotonin on autonomic control of heart rate in intact and baroreceptor deficient rats

The intracerebroventricular (i.c.v.) injection of serotonin (5-HT) increases blood pressure and decreases heart rate (HR) in conscious rats by activation of 5-HT2/1C receptors. Since the bradycardia is eliminated by pretreatment with a ganglionic or V1-vasopressin antagonist, we proposed that the decrease in HR results from an effect on cardiac autonomic activity which is potentiated by vasopressin. The present study aimed first, to further characterize mechanisms by which the i.c.v. injection of 5-HT (2.5 micrograms) decreases HR in conscious rats, and second to determine the cardiovascular responses to 5-HT (2.5 micrograms, i.c.v.) in rats with chronic sinoaortic deafferentation (SAD). In intact rats, the bradycardia elicited by 5-HT was eliminated by a combination of the muscarinic antagonist atropine and the beta-adrenoceptor antagonist sotalol; neither antagonist was effective alone. In rats with SAD, 5-HT produced a larger increase in blood pressure and a marked tachycardia, both of which were eliminated by the 5-HT2/1C antagonist LY 53857. Furthermore, in rats with SAD the 5-HT-induced increase in HR was blocked by sotalol alone. In conclusion, 5-HT (2.5 micrograms, i.c.v.) acts on central 5-HT2/1C receptors to increase arterial pressure. In intact rats this decreases HR by vasopressin-potentiated activation of baroreceptor reflexes and subsequent increase in vagal tone and decrease in cardiac sympathetic tone. In the absence of baroreflexes, a direct central effect of 5-HT to produce a beta-adrenoceptor-mediated cardioacceleration is unmasked.

High-performance liquid chromatographic determination of sotalol in plasma. I. Application to the disposition of sotalol enantiomers in humans

Two high-performance liquid chromatographic analytical methods have been developed for the measurement of dl-sotalol or d-sotalol and l-sotalol in plasma, using dl-atenolol as internal standard. Quantitation of dl-sotalol was carried out, following solid-phase extraction, on a 5-microns C18 reversed-phase column, with a mobile phase containing acetonitrile, ion-pairing reagent and distilled water, using ultraviolet detection at 235 nm. Quantitation of d-sotalol and l-sotalol was based on derivatisation with the chiral agent S-(-)-alpha-methylbenzyl isocyanate, followed by chromatographic separation on a 3-microns C18 reversed-phase column, with a mobile phase containing methanol, glacial acetic acid and distilled water, with fluorimetric detection at 220 nm excitation and 300 nm emission. A preliminary application of the latter method suggests that the disposition of sotalol in humans is not enantioselective.

Hemodynamic effects of the D- and L-isomers of sotalol on normal myocardium

This study investigated the hemodynamic effects of the D-isomer of sotalol in open-chest rats and compared this to the action of the L-isomer and the racemic DL-sotalol. Hemodynamic and additional isovolumic maximum measurements were registered at the end and 5 minutes after an intravenous infusion period of 7 minutes. DL- (1 and 2 mg/kg) and L-sotalol (2 mg/kg) caused a significant reduction in the heart rate and in the indices of contractility during and after infusion. D-sotalol (2, 4, and 8 mg/kg), however, decreased the contractility only transiently after very high doses at high plasma concentrations. Thus, while the effects of the beta-blocking L-isomer were comparable to those of DL-sotalol, only a slight and transient hemodynamic action of comparable doses of D-sotalol was found. These findings may be of significance for the proposed use of the D-isomer as a class-III antiarrhythmic agent.

Life threatening 'epilepsy'

A 5 year old girl presenting with episodes of sudden loss of consciousness was found to have intermittent ventricular tachycardia and, on one occasion, self limiting fibrillation. Corrected QT interval was normal. After several therapeutic measures clinical and electrocardiographic improvement was achieved by administration of sotalol.

Rate dependence of sotalol-induced prolongation of ventricular repolarization during exercise in humans

Studies in animals have shown that drug-induced action potential prolongation with class III antiarrhythmic agents increases with slow pacing rates. We studied the physiological rate dependence of sotalol effects on ventricular repolarization, measured as QT interval duration on the surface electrocardiogram at rest and during a maximal exercise test, in 10 normal volunteers. In a randomized, crossover study, three dosages of sotalol (160 mg/24 hr, 320 mg/24 hr, and 640 mg/24 hr) were administered during 4 days to each subject. In a control period, no drug was administered. During each period, 50-100 QT intervals were measured over a wide range of RR intervals recorded at rest and during the course of a maximal exercise test. Plasma sotalol concentration and beta-adrenoceptor blockade (percent reduction in peak exercise heart rate from control) were also measured. The QT-versus-RR relation was fitted to several formulas, and the overall best fit was used to calculate QT interval duration normalized for a heart rate of 60 beats/min (QTc) and to analyze the rate dependence of QT prolongation with sotalol. Sotalol-induced beta-adrenoceptor blockade and QTc prolongation were dose and concentration dependent. Sotalol reduced peak exercise heart rate by 13.8 +/- 7% at the dosage of 320 mg/24 hr and by 25.4 +/- 8% at the dosage of 640 mg/24 hr (both p less than 0.01). Sotalol prolonged QTc interval by 5.8 +/- 3.7% and 11.8 +/- 3% at these respective dosages (both p less than 0.01). The concentration of sotalol required to produce minimal (mean QTc prolongation, 5.6%; confidence interval, 0-11.2%) QTc prolongation (680 ng/ml) tended to be lower than that required for minimal (mean percent reduction in maximal exercise heart rate, 13.9%; confidence interval, 0-27.8%) beta-blockade (840 ng/ml). QT prolongation with sotalol increased with increasing RR intervals (i.e., decreasing heart rate) at all dosages. QT prolongation became statistically significant for RR of 800 msec or more at all dosages and for RR intervals of 600 msec or more at the dosage of 640 mg/24 hr. This rate dependence altered the relation between QT interval duration and sotalol plasma concentrations. These results suggest that sotalol prolongs QTc interval in humans at dosages and concentrations similar to those required to produce beta-adrenoceptor blockade, QT prolongation with sotalol is more pronounced when heart rate decreases and is not apparent during exercise-induced tachycardia, and the relation between QT prolongation with sotalol and plasma concentrations of the drug depends on the heart rate at which measurements are made.

Sotalol versus class I and II antiarrhythmic agents

In two separate, double-blind, multicenter antiarrhythmic studies, sotalol was compared with propranolol or quinidine using placebo for baseline and/or washout periods. The comparison with quinidine was a crossover study. To be enrolled in these studies, patients were required to have a premature ventricular contraction (PVC) rate of at least 30/hr on a baseline 24-hour ambulatory ECG. At doses calculated to produce equivalent degrees of beta blockade, sotalol was more effective than propranolol in reducing the frequency of PVCs, and the two drugs produced similar reductions in ventricular tachycardia (VT) events. The side effects for sotalol and propranolol were mainly due to beta blockade, and the incidence of side effects with the two drugs was similar. Sotalol was comparable with quinidine in reducing PVCs and VT events. The side effects on sotalol were primarily related to beta-adrenergic blockade, while those on quinidine were predominantly gastrointestinal or neurologic in nature.

Simple in vitro method to characterize antiarrhythmic agents

A simple, nonmicroelectrode method was developed for the in vitro identification and characterization of potential antiarrhythmic agents. To evaluate the method, standard antiarrhythmic agents from three different classifications (I, III, IV) were tested in isolated right ventricular guinea pig papillary muscles for their effect on developed tension (DT), excitability (EX), and effective refractory period (ERP). ERP was measured with the use of paired field stimuli. Depression or reversal of the force frequency relationship was an index of an agent's effect on DT. A shift in the stimulus strength-duration relationship was an index of an agent's effect on EX. A computer program was developed for data handling and analysis. Disopyramide phosphate (D, 3.0 x 10(-5) M), sotalol (S, 3.0 x 10(-5) M), clofilium phosphate (C, 1.0 x 10(-5) M), and N-acetyl procainamide hydrochloride (N, 3.0 x 10(-5) M) significantly prolonged ERP (+20, +35, +24, +16 ms, respectively), while verapamil (V, 3.0 x 10(-7) M) and the distilled water vehicle (W) did not. D and V significantly decreased DT (-78% and -57% at 1 Hz, respectively) while W, S, C, and N did not. Only D decreased EX. These data correspond well with findings in other models reported in the literature, supporting the use of this simple in vitro method for identification and characterization of potential antiarrhythmic agents.