Molecular determinants of pro-arrhythmia proclivity of d- and l-sotalol via a multi-scale modeling pipeline

Drug isomers may differ in their proarrhythmia risk. An interesting example is the drug sotalol, an antiarrhythmic drug comprising d- and l- enantiomers that both block the hERG cardiac potassium channel and confer differing degrees of proarrhythmic risk. We developed a multi-scale in silico pipeline focusing on hERG channel – drug interactions and used it to probe and predict the mechanisms of pro-arrhythmia risks of the two enantiomers of sotalol. Molecular dynamics (MD) simulations predicted comparable hERG channel binding affinities for d- and l-sotalol, which were validated with electrophysiology experiments. MD derived thermodynamic and kinetic parameters were used to build multi-scale functional computational models of cardiac electrophysiology at the cell and tissue scales. Functional models were used to predict inactivated state binding affinities to recapitulate electrocardiogram (ECG) QT interval prolongation observed in clinical data. Our study demonstrates how modeling and simulation can be applied to predict drug effects from the atom to the rhythm for dl-sotalol and also increased proarrhythmia proclivity of d- vs. l-sotalol when accounting for stereospecific beta-adrenergic receptor blocking.

Assessment of the ecotoxicity of the pharmaceuticals bisoprolol, sotalol, and ranitidine using standard and behavioral endpoints

The pharmaceuticals bisoprolol (BIS), sotalol (SOT), and ranitidine (RAN) are among the most consumed pharmaceuticals worldwide and are frequently detected in different aquatic ecosystems. However, very few ecotoxicity data are available in the literature for them. To help fill these data gaps, toxicity tests with the algae Raphidocelis subcapitata, the macrophyte Lemna minor, the cnidarian Hydra attenuata, the crustacean Daphnia similis, and the fish Danio rerio were performed for assessing the ecotoxicity of these pharmaceuticals. Standard, as well as non-standard endpoint, was evaluated, including the locomotor behavior of D. rerio larvae. Results obtained for SOT and RAN showed that acute adverse effects are not expected to occur on aquatic organisms at the concentrations at which these pharmaceuticals are usually found in fresh surface waters. On the other hand, BIS was classified as hazardous to the environment in the acute III category. Locomotor behavior of D. rerio larvae was not affected by BIS and RAN. A disturbance on the total swimming distance at the dark cycle was observed only for larvae exposed to the highest test concentration of 500 mg L^-1 of SOT. D. similis reproduction was affected by BIS with an EC₁₀ of 3.6 (0.1-34.0) mg L^-1. A risk quotient (RQ) of 0.04 was calculated for BIS in fresh surface water, considering a worst-case scenario. To the best of our knowledge, this study presents the first chronic toxicity data with BIS on non-target organisms.

Metal organic framework HKUST-1 modified with carboxymethyl-β-cyclodextrin for use in improved open tubular capillary electrochromatographic enantioseparation of five basic drugs

This work shows that the metal organic framework (MOF) HKUST-1 of type Cu₃(BTC)₂ (also referred to as MOF-199; a face-centered-cubic MOF containing nanochannels) is a most viable coating for use in enantioseparation in capillary electrochromatography (CEC). A HKUST-1 modified capillary was prepared and characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectra, elemental analysis and thermogravimetric analysis. CEC-based enantioseparation of the basic drugs propranolol (PRO), esmolol (ESM), metoprolol (MET), amlodipine (AML) and sotalol (SOT) was performed by using carboxymethyl-β-cyclodextrin as the chiral selector. Compared with a fused-silica capillary, the resolutions are improved (ESM: 1.79; MET: 1.80; PRO: 4.35; SOT: 1.91; AML: 2.65). The concentration of chiral selector, buffer pH value, applied voltage and buffer concentration were optimized, and the reproducibilities of the migration times and R_s values were evaluated. Graphical abstract Schematic presentation of the preparation of a HKUST-1@capillary for enantioseparation of racemic drugs. Cu(NO₃)₂ and 1,3,5-benzenetricarboxylic acid (BTC) were utilized to prepare the HKUST-1@capillary. Then the capillary was applied to construct capillary electrochromatography system with carboxymethyl-β-cyclodextrin (CM-β-CD) for separation of basic racemic drugs.

Compatibility of Baclofen, Carvedilol, Hydrochlorothiazide, Mercaptopurine, Methadone Hydrochloride, Oseltamivir Phosphate, Phenobarbital, Propranolol Hydrochloride, Pyrazinamide, Sotalol Hydrochloride, Spironolactone, Tacrolimus Monohydrate, Ursodeoxycholic Acid, and Vancomycin Hydrochloride Oral Suspensions Compounded with SyrSpend SF pH4

Compounded liquid medication is frequently required in children to allow easy dose adjustment and overcome swallowing difficulties. The objective of this study was to evaluate the stability of oral suspensions compounded with SyrSpend SF PH4 and the commonly used active pharmaceutical ingredients baclofen 2.0 mg/mL, carvedilol 5.0 mg/mL, hydrochlorothiazide 2.0 mg/mL, mercaptopurine 10.0 mg/mL, methadone hydrochloride 10.0 mg/mL, oseltamivir phosphate 6.0 mg/mL, phenobarbital 9.0 mg/mL and 15.0 mg/mL, propranolol hydrochloride 0.5 mg/mL and 5.0 mg/mL, pyrazinamide 100.0 mg/mL, spironolactone 2.0 mg/mL and 2.5 mg/mL, sotalol hydrochloride 5.0 mg/mL, tacrolimus monohydrate 0.5 mg/mL, ursodeoxycholic acid 20.0 mg/mL, and vancomycin hydrochloride 25.0 mg/mL. Suspensions were compounded with raw powders, except for mercaptopurine, pyrazinamide, and sotalol hydrochloride, which were made from commercial tablets. Stability was assessed by measuring the percentage recovery at 0 (baseline), 60 days, and 90 days after compounding for suspensions made with raw powders, which were stored at 2ÅãC to 8ÅãC. The stability of tablets, which were stored at 2ÅãC to 8ÅãC and 20ÅãC to 25ÅãC, was assessed by measuring the percentage recovery at 0 (baseline), 7 days, 14 days, 30 days, 60 days, and 90 days. Active pharmaceutical ingredients quantification was performed by ultraviolet high-performance liquid chromatography via a stability-indicating method. Given the percentage of recovery of the active pharmaceutical ingredients within the suspensions, the beyond-use date of the final products (active pharmaceutical ingredients + vehicle) was at least 90 days for all suspensions in the conditions tested. This suggests that SyrSpend SF PH4 is suitable for compounding active pharmaceutical ingredients from different pharmacological classes.

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

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

Mass spectrometry based in vitro assay investigations on the transformation of pharmaceutical compounds by oxidative enzymes

The ubiquitous presence of trace organic chemicals in wastewater and surface water leads to a growing demand for novel removal technologies. The use of isolated enzymes has been shown to possess the capability for a targeted application but requires a clearer mechanistic understanding. In this study, the potential of peroxidase from horseradish (HRP) and laccase from Pleurotus ostreatus (LccPO) to transform selected trace organic chemicals was studied using mass spectrometry (MS)-based in vitro enzyme assays. Conversion by HRP appeared to be more efficient compared to LccPO. Diclofenac (DCF) and sotalol (STL) were completely transformed by HRP after 4 h and immediate conversion was observed for acetaminophen (APAP). During treatment with LccPO, 60% of DCF was still detectable after 24 h and no conversion was found for STL. APAP was completely transformed after 20 min. Sulfamethoxazole (SMX), carbamazepine (CBZ), ibuprofen (IBP) and naproxen (NAP) were insusceptible to enzymatic conversion. In pharmaceutical mixtures, HRP exhibited a preference for DCF and APAP and the generally less efficient conversion of STL was enhanced in presence of APAP. Transformation product pattern after treatment with HRP revealed polymerization products for DCF while STL showed cleavage reactions. DCF product formation shifted towards a proposed dimeric iminoquinone product in presence of APAP whereas a generally less pronounced product formation in mixtures was observed for STL. In conclusion, the enzymatic treatment approach worked selectively and efficiently for a few pharmaceuticals. However, for application the investigation and possibly immobilization of multiplex enzymes being able to transform diverse chemical structures is recommended.

Risk based in vitro performance assessment of extended release abuse deterrent formulations

High strength extended release opioid products, which are indispensable tools in the management of pain, are associated with serious risks of unintentional and potentially fatal overdose, as well as of misuse and abuse that might lead to addiction. The issue of drug abuse becomes increasingly prominent when the dosage forms can be readily manipulated to release a high amount of opioid or to extract the drug in certain products or solvents. One approach to deter opioid drug abuse is by providing novel abuse deterrent formulations (ADF), with properties that may be viewed as barriers to abuse of the product. However, unlike regular extended release formulations, assessment of ADF technologies are challenging, in part due to the great variety of formulation designs available to achieve deterrence of abuse by oral, parenteral, nasal and respiratory routes. With limited prior history or literature information, and lack of compendial standards, evaluation and regulatory approval of these novel drug products become increasingly difficult. The present article describes a risk-based standardized in-vitro approach that can be utilized in general evaluation of abuse deterrent features for all ADF products.

Pharmacometabolomic approach to predict QT prolongation in guinea pigs

Drug-induced torsades de pointes (TdP), a life-threatening arrhythmia associated with prolongation of the QT interval, has been a significant reason for withdrawal of several medicines from the market. Prolongation of the QT interval is considered as the best biomarker for predicting the torsadogenic risk of a new chemical entity. Because of the difficulty assessing the risk for TdP during drug development, we evaluated the metabolic phenotype for predicting QT prolongation induced by sparfloxacin, and elucidated the metabolic pathway related to the QT prolongation. We performed electrocardiography analysis and liquid chromatography-mass spectroscopy-based metabolic profiling of plasma samples obtained from 15 guinea pigs after administration of sparfloxacin at doses of 33.3, 100, and 300 mg/kg. Principal component analysis and partial least squares modelling were conducted to select the metabolites that substantially contributed to the prediction of QT prolongation. QTc increased significantly with increasing dose (r = 0.93). From the PLS analysis, the key metabolites that showed the highest variable importance in the projection values (>1.5) were selected, identified, and used to determine the metabolic network. In particular, cytidine-5'-diphosphate (CDP), deoxycorticosterone, L-aspartic acid and stearic acid were found to be final metabolomic phenotypes for the prediction of QT prolongation. Metabolomic phenotypes for predicting drug-induced QT prolongation of sparfloxacin were developed and can be applied to cardiac toxicity screening of other drugs. In addition, this integrative pharmacometabolomic approach would serve as a good tool for predicting pharmacodynamic or toxicological effects caused by changes in dose.

Excimer formation in inclusion complexes of β-cyclodextrin with salbutamol, sotalol and atenolol: spectral and molecular modeling studies

The inclusion complexation behavior of salbutamol, sotalol and atenolol drugs with β-cyclodextrin (β-CD) were investigated by UV-visible, fluorometry, time resolved fluorescence, FT-IR, (1)H NMR, SEM and PM3 methods. The above drugs gave a single emission maximum in water where as dual emission in β-CD. In β-CD solutions the shorter wavelength fluorescence intensity was regularly decreased and longer wavelength fluorescence intensity increased. Addition of β-CD to aqueous solutions of drugs resulted into excimer emission. The excimer emission is concluded to be due to a 1:2 inclusion complex between β-CD and drug. Nanosecond time-resolved studies indicated that all drugs exhibited biexponential decay in solvents and triexponential decay in CD. Investigations of thermodynamic and electronic properties confirmed the stability of the inclusion complex.

Occurrence and removal of pharmaceuticals and hormones through drinking water treatment

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

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.

Stability of sotalol in two liquid formulations at two temperatures

BACKGROUND

Sotalol is used in certain pediatric patients to treat, suppress, or prevent the recurrence of life-threatening ventricular arrhythmias. However, it is commercially unavailable in a liquid dosage form. The use of an extemporaneously prepared liquid dosage form must be supported by the documentation of the chemical and physical stability of sotalol.

OBJECTIVE

To determine the stability of sotalol hydrochloride extemporaneously prepared from tablets in 2 oral suspensions stored at 2 temperatures.

METHODS

Five bottles contained Ora Plus:Ora Sweet (1:1) and the other 5 bottles had 1% methylcellulose:simple syrup NF (1:9), with a sotalol concentration of 5 mg/mL. Three samples were collected from each bottle at 0, 7, 14, 28, 42, 56, 70, and 91 days and analyzed by a stability-indicating HPLC analytical method (n = 15).

RESULTS

At 4 degrees C, the mean concentration of sotalol was at least 98.9% of the original concentration in Ora Plus:Ora Sweet suspension and 95.5% of the initial concentration in 1% methylcellulose:simple syrup during storage for 3 months. At 25 degrees C, the mean concentration of sotalol was >/=95.5% of the original concentration in Ora Plus:Ora Sweet suspension and 94.4% of the initial concentration in 1% methylcellulose:simple syrup during storage for 3 months. The pH did not change substantially during the study period. Further, no changes in physical appearance were seen during the study.

CONCLUSIONS

Sotalol hydrochloride can be prepared in either of 2 liquid dosage forms and stored in plastic bottles for 13 weeks at 4 or 25 degrees C without substantial loss of potency.

Buccal transport of flecainide and sotalol: effect of a bile salt and ionization state

Patients with infrequent attacks of supraventricular arrhythmia may benefit from self administration of antiarrhythmic drugs on an 'as required' basis. The oral cavity is easily accessible and the potential for rapid absorption exists. The effects of ionization state and sodium glycocholate on the ex vivo transport of sotalol and flecainide across porcine buccal mucosa were studied. The permeated amounts at 3 h (Q) and fluxes (J) of sotalol in an aqueous solution at pH 7.4 and 9.0 were similar. At pH 7.4, in contrast to pH 9.0, the addition of 1.0% (w/v) sodium glycocholate decreased Q and J four and five fold. Flecainide base in propylene glycol resulted in a nine and 12 fold higher Q and J as compared with an aqueous solution of flecainide acetate at pH 5.8. The presence of sodium glycocholate reduced the transport rate of the flecainide base. However, Q and J were increased 110 and 75 fold by adding 1.0% (w/v) sodium glycocholate to a solution of flecainide acetate at pH 5.8. Sodium glycocholate seems to be an effective penetration enhancer for the buccal absorption of the more polar ionized form of flecainide in an aqueous solution. Sodium glycocholate does not seem to improve the transport of sotalol.

Kinetic disposition of (+)-S- and (-)-R-sotalol enantiomers in cardiac patients with tachyarrhythmias using an improved HPLC-fluorescence stereoselective method

Since the enantioselective pharmacokinetic profiles of R,S-sotalol in cardiac patients are controversial, the present investigation aimed to study the kinetic disposition of sotalol enantiomers in patients with tachycardia. Thirteen cardiac patients, who gave their written consent, were included (6F/7M; 53 +/- 12 yrs, 66 +/- 13 kg, 163 +/- 8 cm height). They had tachycardia, normal renal function and had been chronically treated with tablets of sotalol 160 mg b.i.d. The patients were submitted to blood samples collection at zero, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 10 and 12 h after drug administration. The quantitation of sotalol enantiomers were performed by a stereoselective HPLC method with fluorescence detection previously published. A one open compartment model was applied and the main pharmacokinetic parameters obtained for R-/S-sotalol were, respectively (Mean +/- SD): CSSMAX = 1007 +/- 307/1040 +/- 340 ng/mL; TMAX = 1.82 +/- 0.6/1.83 +/- 0.6 h; AUCSST = 6959 +/- 2153/7388 +/- 2563 ng.h/mL; CISSr/F = 2.7 +/- 1.2/2.5 +/- 1.2 mL/min/kg and VdSS/F = 1.9 +/- 0.9/2.0 +/- 1.0 L/kg. The pharmacokinetic parameters of R,S-sotalol were within the published range and the kinetic parameters for the isomers were grouped as two independent samples and statistically compared. In conclusion, stereoselective pharmacokinetic for sotalol was not observed in cardiac arrhythmic patients, i.e., both R- and S-sotalol enantiomers have the same pharmacokinetic profile.

Drug release from a porous ion-exchange membrane in vitro

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

Effect of diffusion potential, osmosis and ion-exchange on transdermal drug delivery: theory and experiments

Equations expressing the effect of the diffusion potential on the trace ion transfer across a porous charged membrane have been derived. These equations have been tested with experiments with human cadaver skin. The transfer of sotalol and salicylate was measured varying the salt (NaCl) concentration in the donor and receiver compartments. It appears that osmotic pressure and ion-exchange make a significant contribution to the flux enhancement by the diffusion potential.

Short-term myocardial uptake of d- and l-sotalol in humans: relation to hemodynamic and electrophysiologic effects

The myocardial concentration of many cardioactive drugs has been identified as an important determinant of their short-term effects in previous studies. Although sotalol is frequently administered via short-term intravenous injection, no previous studies had sought to correlate its uptake by the heart with its various effects. We determined the time course of short-term uptake of d,l-sotalol by human myocardium in vivo and investigated the relation between myocardial content of sotalol and the short-term hemodynamic, electrocardiographic, and electrophysiologic effects of the drug. Sixteen patients received a 20-mg intravenous bolus of sotalol at the time of diagnostic cardiac catheterization. Myocardial content of d- and l-sotalol (by using a paired transcoronary sampling technique) and the short-term hemodynamic and electrophysiologic effects of the drug were determined < or = 20 min after injection. Myocardial accumulation of sotalol was not enantioselective, proceeded very rapidly (maximal at 0.74 +/- 0.10 min, representing 2.05 +/- 0.45% of the total injected dose), and was not significantly influenced by left ventricular systolic function or the extent of coronary artery disease. Approximately one third of peak myocardial content was still present 17.5 min after sotalol administration. Maximal effects of the drug (reduction in spontaneous heart rate, p < 0.005; reduction in maximal rate of LV pressure increase (LV+dP/dtmax, p < 0.005); and prolongation of PR intervals, p < 0.02) were delayed by approximately 10 min relative to maximal myocardial sotalol content. The significant prolongation of AH intervals (p < 0.01) and atrioventricular nodal effective refractory periods (p < 0.0002) that was observed was also maximal 10 min after administration of sotalol. Thus a consistent delay between myocardial sotalol content and the short-term effects of the drug was observed. In conclusion, the accumulation of both d- and l-sotalol by the human myocardium is more rapid than that of any other agent studied to date, with considerable hysteresis between myocardial drug uptake and subsequent cardiac effects.

Inhibition by Compound II, a sotalol analogue, of delayed rectifier current (iK) in rabbit isolated sino-atrial node cells

The effects of Compound II, a sotalol analogue, on spontaneous electrical activity and on three membrane currents (the delayed rectifier current, iK, the long-lasting inward calcium current, i(Ca,L) and hyperpolarization activated inward current, i(f)) were investigated in rabbit isolated sino-atrial node cells by whole cell clamp with amphotericin-permeabilised patches. A submaximal concentration of Compound II (50 nM) had a significant effect on the time and voltage dependent activation of iK and caused a positive shift of the iK activation curve. As well as blocking i(Kr), it caused some degree of block of i(Ks). Block of iK by Compound II was found to be concentration dependent with an IC50 of approximately 40 nM. 1 microM Compound II nearly completely blocked iK without significantly affecting the peak current or I/V relationships of i(Ca,L) or i(f). 50 nM Compound II caused a significant prolongation of APD100 and of cycle length. It also decreased diastolic depolarization rate without significantly affecting MDP and action potential amplitude. It is concluded that Compound II, a sotalol analogue, slows spontaneous activity of isolated rabbit SA node cells through a selective inhibition of iK.

Positive and negative inotropic effects of DL-sotalol and D-sotalol in failing and nonfailing human myocardium under physiological experimental conditions

BACKGROUND

DL-Sotalol has class III antiarrhythmic activity through prolongation of the repolarization phase of the action potential as well as beta-adrenoceptor-blocking properties. Although the former effect was found to exert positive inotropic effects in animal experimental studies, the latter may be detrimental in heart failure due to negative inotropism. In contrast to DL-sotalol, D-sotalol is suggested to exert only positive inotropic effects, which were never tested in isolated human myocardium.

METHODS AND RESULTS

Therefore, we investigated the effects of racemic DL-sotalol and its enantiomer D-sotalol in human right atrial muscle strip preparations and in left ventricular muscle strip preparations from nonfailing and end-stage failing human hearts. DL-sotalol and D-sotalol significantly (P < .01) increased peak developed force in atrial preparations by 14.0 +/- 3.4% and 16.7 +/- 3.8%, respectively, but had no effect in ventricular myocardium. In nonfailing ventricular myocardium, both DL-sotalol and D-sotalol shifted the dose-response curve for isoproterenol to higher concentrations (P < .01); however, DL-sotalol was 100-fold more effective than D-sotalol. In non-failing myocardium, a positive force-frequency relation was found between 30 and 120 beats per minute, but isoproterenol was much more powerful in its inotropic effects. In failing myocardium, reduction in stimulation rate from 120 to 30 beats per minute increased peak developed force more pronounced than did the application of isoproterenol.

CONCLUSIONS

(1) D-Sotalol has no relevant beta-adrenoceptor-blocking activity compared with DL-sotalol. (2) Neither DL-sotalol nor D-sotalol exhibit positive inotropic effects in human left ventricular myocardium. (3) Heart rate reduction increases contractile force in end-stage failing human myocardium due to an inverse force-frequency relation and thereby counteracts the potential negative inotropic properties of beta-blockade.

Sotalol: a new beta-adrenergic blocker for ventricular arrhythmias

Sotalol is a water-soluble, nonselective, beta-adrenergic blocker that was recently approved in oral form in the United States for the treatment of ventricular arrhythmias that are judged to be life-threatening. As a beta-blocker, sotalol is unique in having additional class-III antiarrhythmic activity. It is still not resolved whether sotalol is more effective than other beta-blockers in managing arrhythmias, but there are suggestions that it might possess greater antiarrhythmic and life-protecting activities than other types of antiarrhythmic drugs. The drug is well tolerated, but, because of its electrophysiologic activity, there is a small risk of proarrhythmia, specifically the development of polymorphic ventricular tachycardia and torsade de pointes.

Electrophysiological mechanisms of action of the levorotatory isomer of sotalol in a canine infarct model of inducible ventricular tachycardia: comparison with the beta-1 receptor antagonist bisoprolol

To evaluate the antiarrhythmic efficacy of l-sotalol and bisoprolol on inducible ventricular arrhythmias, conscious dogs with 4- to 8-day-old myocardial infarction were studied by programmed electrical stimulation. Direct recordings from infarcted and adjacent normal subepicardium were made using a specially designed composite electrode. From 18 dogs developing sustained ventricular tachycardia (sVT) during control stimulation, l-sotalol (1.5 mg/kg i.v.) prevented reinducibility of sVT in 10 animals, while in seven other animals it significantly reduced the rate of tachycardia. Bisoprolol (0.2 mg/kg i.v.), tested in a separate group of 10 dogs susceptible to sVT, was mostly ineffective in preventing or slowing the tachycardia. Both agents significantly prolonged conduction time and refractoriness within the atrioventricular conduction system, and decreased heart rate. However, while l-sotalol lengthened ventricular refractoriness and QT interval, bisoprolol exerted only a minor effect on these parameters. Neither of the drugs affected conduction in normal and infarcted myocardium, as indicated by almost unchanged QRS complex width and duration of ventricular late potentials, respectively. The results indicate that acute beta-blockade is ineffective against sVT induced during the subacute stage of myocardial infarction. The antiarrhythmic efficacy of l-sotalol may predominantly be related to its prolonging effect on ventricular refractoriness, supporting the concept of pure class III action.

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.

Pharmacokinetic and pharmacodynamic profiles of d-sotalol and d,l-sotalol

d,l-Sotalol is a racemic drug composed of equimolar amounts of d-(+)-sotalol and l-(-)-sotalol. The l-(-)-enantiomer has both beta-blocking (class II) activity and potassium-channel-blocking (class III) properties. The d-(+)-enantiomer has class III properties similar to those of l-sotalol. However, the affinity of d-sotalol for beta-adrenergic receptors is 30 to 60 times lower than the affinity of l-sotalol. The pharmacokinetics of d,l-sotalol are linear. Following oral administration, absorption and bioavailability are almost complete; apparent elimination half-life ranges from 7 to 18 hours. More than 80% of racemic sotalol elimination occurs by renal excretion of unchanged drug. Sotalol is not metabolized, nor is it significantly bound to plasma proteins. Thus, steady-state plasma concentration is reached within 3 days of treatment onset in patients without renal insufficiency. Dosage of sotalol should be adjusted to creatinine clearance. The pharmacokinetic profile of d-sotalol is similar to that of the racemate. Plasma concentrations of racemic sotalol associated with beta-adrenergic blockade are similar to those associated with its class III actions. QT interval prolongation with d,l-sotalol is dose- and concentration-dependent and decreases at rapid heart rates. Also, QT interval prolongation at a given plasma concentration during repeated dosing tends to be less pronounced than QT prolongation at the same plasma concentration during single dosing. The class III actions of d-sotalol in the sinus node are associated with slowing of sinus heart rate, whereas additional beta blockade contributes to the decrease in heart rate observed with l- or d,l sotalol.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of sotalol and d-sotalol on ventricular tachycardia and fibrillation induced by programmed electrical stimulation

It is only in the last few years that the broad-spectrum antiarrhythmic properties of sotalol have become increasingly recognized. Racemic sotalol has potent beta-blocking and class III antiarrhythmic properties, and it has been reported that this drug is able to control supraventricular and ventricular arrhythmias. Recently, several studies performed with the d-sotalol isomer, which is almost devoid of the beta-blocking effects compared to the racemate, suggest significant antiarrhythmic efficacy and good tolerance of the dextro-isomer. In this paper we review and discuss the effects of sotalol and d-sotalol in patients with ventricular tachycardia (VT), ventricular fibrillation (VF) or cardiac arrest in whom VT or VF was induced by programmed electrical stimulation (PES).

Acute and chronic antiarrhythmic efficacy of d-sotalol in patients with sustained ventricular tachyarrhythmias

To evaluate the clinical efficacy of d-sotalol, 84 patients with a history of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF), who had inducible sustained VT/VT at baseline electrophysiologic study (EPS), were investigated after intravenous (IV) d-sotalol (1.5-2.5 mg.kg-1). A total of 29 additional patients received only oral d-sotalol, (400-600 mg.day-1). Acute success of antiarrhythmic therapy was defined as suppression of inducible sustained VT/VF. The overall success rate of IV d-sotalol was 38% (32/84) after a mean of 4.3 drugs failed to suppress inducibility. A 78% success rate (31/40) was demonstrated in patients who were also assessed after oral d-sotalol. Torsade de pointes type VT was seen in one patient. After 1 year, only 16% of patients with a positive EPS had a recurrence compared to 43% of patients with a negative EPS (P < 0.05). Estimated survival rates were 95 and 88% after 1 and 2 years of follow-up, respectively. Only five of 56 patients discontinued d-sotalol therapy because of adverse effects. IV d-sotalol appears to be an effective antiarrhythmic agent. Its long-term efficacy is predictable on the basis of therapy guided by electrophysiologic testing in patients with refractory ventricular tachyarrhythmias. The efficacy of d-sotalol seems comparable to that reported for d,l-sotalol.

Electrophysiologic properties of sotalol and d-sotalol. A current view

Although discovered more than two decades ago, the clinical applications of sotalol are still a matter of debate. Together with amiodarone, sotalol is considered a prototype of a new class of antiarrhythmic agents characterized by repolarization-prolonging effects (class III). Lengthening of repolarization is associated with an increase in the effective refractory period of cardiac tissues. There is no change in the maximum rate of rise during phase 0, a finding that supports the lack of sotalol effect on the fast sodium channel. The electrophysiologic action of the drug in humans provides evidence for direct cardiac effects of sotalol in addition to beta blockade. The beta-blocking properties play a major role in the sinus-rate slowing and lengthening of the atrioventricular nodal conduction time observed after sotalol administration. However, the drug also prolongs refractoriness in atria, His-Purkinje tissue, ventricular muscle and accessory atrioventricular connections. These latter changes are absent or minimal with conventional beta blockers and are likely to reflect sotalol-induced prolongation of cardiac repolarization. They result in an increase in the QT interval, an effect that is dose-dependent and more marked during chronic therapy. The dextrorotatory isomer, d-sotalol, shares a similar electrophysiologic profile. Lengthening of repolarization in cardiac cells following d-sotalol is of the same magnitude as that produced by the levoisomer. This finding provides further evidence for a class III action of sotalol, as the dextroisomer is almost devoid of beta-blocking properties. In humans, the electrical effects of both drugs are similar. However, d-sotalol-induced changes in sinus rate and atrioventricular nodal conduction are modest.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical role of d-sotalol and d,l-sotalol in supraventricular arrhythmias, including pre-excitation

Numerous trials performed over the last 20 years, although uncontrolled, have shown the racemic d,l-sotalol is effective for the acute conversion and for long-term prevention of recurrences of supraventricular tachyarrhythmias. Sotalol appeared to be moderately effective in atrial fibrillation or atrial flutter, having somewhat greater efficacy in the case of atrioventricular (AV) nodal re-entrant tachycardia due to Wolff-Parkinson-White syndrome or concealed accessory pathway. These effects may stem from the combined class II and class III electrophysiologic properties of this drug. However, studies comparing d,l-sotalol to pure beta blockers in different 'models', especially postsurgical arrhythmias and Wolff-Parkinson-White syndrome, have suggested that the observed clinical benefit may be related to d,l-sotalol's class III properties. Thus, d-sotalol may be efficacious in these indications. Its precise efficacy should be defined in controlled clinical trials.

Inotropic and haemodynamic effects of d- and d,l-sotalol: comparison with other antiarrhythmics

The inotropic effects of sotalol in comparison to other antiarrhythmic drugs were tested in an experimental model allowing isovolumic measurements independently of the loading conditions. All class I drugs had a similar negative inotropic effect. d,l-Sotalol caused a dose-dependent depressant effect on the rate of left ventricular pressure development. The same held true for l-sotalol. In contrast, d-sotalol, in clinical doses, revealed no significant inotropic effects in normal hearts. In a postischemic model, d-sotalol led to a further deterioration of left ventricular function. It could be demonstrated by autonomic blockade that this effect was mainly the result of the remaining weak beta-blocking activity of the d-isomer in addition to its class III action. After intravenous administration of amiodarone in doses of 10 mg.kg-1, no significant inotropic effects were found in normal rats.

The effects of (+/-)-, (+)-, and (-)-atenolol, sotalol, and amosulalol on the rat left atria and portal vein

The effects of (+/-)-, (+)-, and (-)-atenolol, sotalol, and amosulalol alone on the rat left atria and portal vein and on the respective beta 1- and beta 2-adrenoceptor-mediated responses to isoprenaline have been determined. (+/-)-Atenolol at 10(-6) M had no effect whereas high concentrations of (+/-)- and (-)-sotalol, 10(-5)-10(-4) M, and (+/-)-, and (-)-amosulalol depressed the response of the rat left atria to cardiac stimulation which indicates membrane stabilizing activity. None of the drugs tested had any effect alone on the rat portal vein. The order of potency as antagonists was (+/-)-amosulalol > (+/-)-atenolol > (+/-)-sotalol at beta 1-adrenoceptors and (+/-)-amosulalol > (+/-)-sotalol > (+/-)-atenolol at beta 2-adrenoceptors. (+/-)-Atenolol and (+/-)-amosulalol are beta 1-selective whereas (+/-)-sotalol is beta 2-selective. For each of the racemic beta-blockers, the beta 1- and beta 2-adrenoceptor blocking activity was predominantly due to the (-)-enantiomer.