Pharmacology, pharmacodynamics and pharmacokinetics of sotalol

Feasibility and Safety of Intravenous Sotalol Loading in Adult Patients With Atrial Fibrillation (DASH-AF)

BACKGROUND

Inpatient initiation of sotalol is recommended owing to its proarrhythmic effects. The DASH-AF (Feasibility and Safety of Intravenous Sotalol Administered as a Loading Dose to Initiate Oral Sotalol Therapy in Adult Patients With Atrial Fibrillation) trial evaluates the safety and feasibility of intravenous (IV) sotalol, achieving a steady state with maximum QTc prolongation within 6 hours instead of the traditional 5-dose inpatient oral (PO) titration.

METHODS

DASH-AF is a prospective, nonrandomized, multicenter, open-label trial consisting of patients who underwent IV sotalol loading dose to initiate rapid oral therapy for atrial arrhythmias. IV dose was calculated based on the target oral dose as indicated by baseline QTc and renal function. Patients' QTc (in sinus) was measured via electrocardiography at 15-minute intervals and after IV loading completion. Patients were discharged 4 hours after first oral dose. All patients were monitored via mobile cardiac outpatient telemetry for 72 hours. The control group was composed of patients admitted for the traditional 5 PO doses. Safety outcomes were assessed in both groups.

RESULTS

One hundred twenty patients from 3 centers were enrolled from 2021 to 2022 in the IV loading group (compared with type of AF- and renal function-matched patients in the conventional PO loading cohort). This study demonstrated no significant change in ΔQTc in both groups, with a significantly lower number of patients requiring dose adjustment in the IV arm compared with the PO arm (4.1% vs 16.6%; P = 0.003). This led to potential cost savings of up to $3,500.68 per admission.

CONCLUSIONS

The DASH-AF trial shows that rapid IV sotalol loading in atrial fibrillation/flutter patients for rhythm control is feasible and safe compared with conventional oral loading with significant cost reduction. (Feasibility and Safety of Intravenous Sotalol Administered as a Loading Dose to Initiate Oral Sotalol Therapy in Adult Patients With Atrial Fibrillation [DASH-AF]; NCT04473807).

Prediction of drug pro-arrhythmic cardiotoxicity using a semi-physiologically based pharmacokinetic model linked to cardiac ionic currents inhibition

Drug-induced torsades de pointes (TdP) risks are responsible for the withdrawal of many drugs from the market. Nowadays, assessments of drug-induced TdP risks are mainly based on maximum effective free therapeutic plasma concentration (EFTPCmax) and cardiac ionic current inhibitions using the human ventricular myocytes model (Tor-ORd model). Myocytes are targets of drug-induced TdP. The TdP risks may be directly linked to myocyte drug concentrations. We aimed to develop a semi-physiologically based pharmacokinetic (Semi-PBPK) model linked to cardiac ionic current inhibition (pharmacodynamics, PD) (Semi-PBPK-PD) to simultaneously predict myocyte drug concentrations and their TdP risks in humans. Alterations in action potential duration (ΔAPD90) were simulated using the Tor-ORd model and ionic current inhibition parameters based on myocyte or plasma drug concentrations. The predicted ΔAPD90 values were translated into in vivo alterations in QT interval(ΔQTc) induced by moxifloxacin, dofetilide, or sotalol. Myocyte drug concentrations of moxifloxacin, dofetilide, and sotalol gave better predictions of ΔQTc than plasma. Following validating the developed semi-PBPK-PD model, TdP risks of 37 drugs were assessed using ΔAPD90 and early afterdepolarization occurrence, which were estimated based on 10 × EFTPCmax and 10 × EFTMCmax (maximum effective free therapeutic myocyte concentration). 10 × EFTMCmax gave more sensitive and accurate predictions of pro-arrhythmic cardiotoxicity and the predicted TdP risks were also closer to clinic practice than 10 × EFTPCmax. In conclusion, pharmacokinetics and TdP risks of 37 drugs were successfully predicted using the semi-PBPK-PD model. Myocyte drug concentrations gave better predictions of ΔQTc and TdP risks than plasma.

Comparative Safety and Effectiveness of Sotalol Versus Dronedarone After Catheter Ablation for Atrial Fibrillation

Background Atrial tachyarrhythmias are common after atrial fibrillation ablation, so adjunctive antiarrhythmic drug therapy is often used. Data on the effectiveness and safety of dronedarone and sotalol after AF ablation are limited. Here, we compared health outcomes of ablated patients treated with dronedarone versus sotalol. Methods and Results A comparative analysis of propensity score-matched retrospective cohorts was performed using IBM MarketScan Research Databases. Patients treated with dronedarone after atrial fibrillation ablation were matched 1:1 to patients treated with sotalol between January 1, 2013 and March 31, 2018. Outcomes of interest included cardiovascular hospitalization, proarrhythmia, repeat ablation, and cardioversion. This study was exempt from institutional review board review. Among 30 696 patients who underwent atrial fibrillation ablation, 2086 were treated with dronedarone and 3665 with sotalol after ablation. Propensity-score matching resulted in 1815 patients receiving dronedarone matched 1:1 to patients receiving sotalol. Risk of cardiovascular hospitalization was lower with dronedarone versus sotalol at 3 months (adjusted hazard ratio [aHR], 0.77 [95% CI, 0.61-0.97]), 6 months (aHR, 0.76 [95% CI, 0.63-0.93]), and 12 months after ablation (aHR, 0.70 [95% CI, 0.66-0.93]). Risk of repeat ablation and cardioversion generally did not differ between the 2 groups. A lower risk of proarrhythmia was associated with dronedarone versus sotalol at 3 months (aHR, 0.76 [95% CI, 0.64-0.90]), 6 months (aHR, 0.80 [95% CI, 0.70-0.93]), and 12 months (aHR, 0.83 [95% CI, 0.73-0.94]) after ablation. Conclusions These data suggest that dronedarone may be a more effective and safer alternative after ablation than sotalol.

Model-Informed Development of Sotalol Loading and Dose Escalation Employing an Intravenous Infusion

BACKGROUND

Sotalol is often employed to prevent recurrence of symptomatic atrial flutter/atrial fibrillation. Because sotalol can prolong the QT interval excessively causing ventricular arrhythmias, a 3-day in-hospital loading or dose escalation period is mandated with oral administration in the product label for patient safety. In patients with normal renal function, 3 days (five oral doses) are required to obtain steady state maximum sotalol concentration, which results in maximum QT prolongation. The aim of this study is to develop an intravenous to oral loading regime for sotalol therapy that reduces the 3-day in-hospital initiation or dose escalation with oral administration to 1 day without compromising patient safety.

METHODS

Using model-informed drug development techniques, simulations were developed for initiation and dose escalation of sotalol therapy by employing an intravenous loading dose followed by oral sotalol administrations.

RESULTS

In patients with normal renal function, an initial 1-h loading dose of intravenous sotalol followed by two oral doses in 24 h has been developed permitting attainment of three maximum serum concentrations reflecting maximum QT prolongation in a 1-day observation period. Dosing regimens for patients with impaired renal function are also developed.

CONCLUSIONS

In patients with normal renal function, using an intravenous loading dose followed by oral administrations permits safe initiation or dose escalation of sotalol in 1 day instead of the 3-day dosing regimen with oral administration.

Intravenous Sotalol in the Young: Safe and Effective Treatment With Standardized Protocols

OBJECTIVES

This study assessed the safety and efficacy of novel and standardized protocols for the use of intravenous (IV) sotalol in pediatric patients.

BACKGROUND

Acute arrhythmia treatments in children remain limited. IV sotalol is a new option but pediatric experience is limited. There is no standardized protocol for rapid infusion during acute arrhythmias. This study assessed a single center's initial experience with IV sotalol in young patients, describing a protocol for rapid infusion for acute treatment, and reviewed the safety and efficacy of maintenance dosing.

METHODS

This is a retrospective study of all patients who received IV sotalol at Rady Children's Hospital. Demographics, arrhythmia, hemodynamics, and effects of IV sotalol were assessed.

RESULTS

Thirty-seven patients received IV sotalol from December 2015 to December 2018. Group 1 (n = 26) received sotalol for acute therapy and group 2 (n = 11) received a maintenance dose of sotalol after successful cardioversion with alternate therapies. The groups had similar demographics. Group 1 included patients with atrial flutter (n = 16), patients with supraventricular tachycardia (SVT) (n = 9), and patients with atrial ectopic tachycardia (AET) (n = 1). All 9 patients with SVT (100%) converted to sinus rhythm after failure to convert using adenosine. Median administration time was 15 min, the median dose was 30 mg/m², and mean time to cardioversion was 14 min. Group 2 median infusion time was 120 min, the median dose was 54 mg/m²/day, and all patients maintained sinus rhythm. No patients required cessation for adverse effects previously described for IV sotalol.

CONCLUSIONS

IV sotalol was safe and effective for acute and maintenance therapy in young patients. In acute patients, 30 mg/m² over 15 min converted most patients. IV sotalol adds a valuable option to IV therapies in the young.

Efficacy of β-blocker therapy for secondary prevention for patients undergoing coronary artery bypass grafting surgery

PURPOSE OF REVIEW

The efficacy and safety of β-blockers in the treatment of cardiovascular diseases, such as ischemic heart disease, cardiac arrhythmias, and heart failure, have been well established for decades. In this article, we review the current opinions on the application of β-blockers for secondary prevention in patients undergoing coronary artery bypass grafting (CABG) surgery.

RECENT FINDINGS

As the average age of patients treated surgically for coronary artery disease (CAD) is increasing, it is not uncommon to have candidates for CABG presenting with concomitant atrial fibrillation, heart failure or hypertension, most of which were caused by excessive activation of the adrenergic nervous system. In a recent decade, a number of national quality-improvement efforts using a variety of techniques have been made to increase the use of β-blocker therapy before or following the CABG. Results from recent large observational studies among patients with CAD showed that β-blockers were associated with a lower risk of cardiac events only among those with heart failure or recent myocardial infarction. However, the consistent use of β-blockers could benefit those with or without prior myocardial infarction who underwent CABG and discharged alive.

SUMMARY

In real-world clinical practice, β-blockers are effective and safe to control heart rate and symptoms in patients with CAD, especially for those concomitant with left ventricular systolic dysfunction or prior myocardial infarction. Current evidence supports the preoperative use of β-blocker therapy for patients undergoing CABG as a prevention of new-onset atrial fibrillation. It is reasonable to continue β-blockers as chronic therapy in all CABG patients without contraindications after hospital discharge. Further strategies should be developed to understand and improve discharge prescription of β-blockers and long-term patient adherence.

Intestinal permeability study of minoxidil: assessment of minoxidil as a high permeability reference drug for biopharmaceutics classification

The purpose of this study was to evaluate minoxidil as a high permeability reference drug for Biopharmaceutics Classification System (BCS). The permeability of minoxidil was determined in in situ intestinal perfusion studies in rodents and permeability studies across Caco-2 cell monolayers. The permeability of minoxidil was compared with that of metoprolol, an FDA reference drug for BCS classification. In rat perfusion studies, the permeability of minoxidil was somewhat higher than that of metoprolol in the jejunum, while minoxidil showed lower permeability than metoprolol in the ileum. The permeability of minoxidil was independent of intestinal segment, while the permeability of metoprolol was region-dependent. Similarly, in mouse perfusion study, the jejunal permeability of minoxidil was 2.5-fold higher than that of metoprolol. Minoxidil and metoprolol showed similar permeability in Caco-2 study at apical pH of 6.5 and basolateral pH of 7.4. The permeability of minoxidil was independent of pH, while metoprolol showed pH-dependent transport in Caco-2 study. Minoxidil exhibited similar permeability in the absorptive direction (AP-BL) in comparison with secretory direction (BL-AP), while metoprolol had higher efflux ratio (ER > 2) at apical pH of 6.5 and basolateral pH of 7.4. No concentration-dependent transport was observed for either minoxidil or metoprolol transport in Caco-2 study. Verapamil did not alter the transport of either compounds across Caco-2 cell monolayers. The permeability of minoxidil was independent of both pH and intestinal segment in intestinal perfusion studies and Caco-2 studies. Caco-2 studies also showed no involvement of carrier mediated transport in the absorption process of minoxidil. These results suggest that minoxidil may be an acceptable reference drug for BCS high permeability classification. However, minoxidil exhibited higher jejunal permeability than metoprolol and thus to use minoxidil as a reference drug would raise the permeability criteria for BCS high permeability classification.

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

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

Beneficial cardiac effects of cicletanine in conscious rabbits with metabolic syndrome

BACKGROUND AND PURPOSE

High-fat diet and consequent metabolic syndrome (MS) can lead to elevated risk for cardiac arrhythmias. This preclinical study was to investigate if cicletanine (CIC) could produce cardioprotective effects in conscious rabbits exhibiting the main symptoms of MS.

METHODS

NZW rabbits that had undergone an 8-week-long cholesterol-enriched diet (1.5%) were instrumented with a pacemaker electrode and randomly assigned into 3 groups according to the oral treatment of either CIC (50 mg·kg) or sotalol (25 mg·kg) and their placebo b.i.d. over 5 days. Study groups were subjected to either "arrhythmia challenge" by programmed electrical stimulation in the "Arrhythmogenesis" study (N = 54) or global myocardial ischemia by rapid pacing in the "Ventricular Overdrive Pacing-induced Myocardial Ischemia" study (N = 18). The antiarrhythmic effect was evaluated by the establishment of the incidence of programmed electrical stimulation-induced arrhythmias. Proarrhythmia indicators (eg, QTc, Tpeak-Tend) were also measured to assess the cardiac safety profile of CIC. To evaluate the background of antiarrhythmic effect, cardiac cyclic nucleotide (cyclic 3',5'-guanosine monophosphate [cGMP], cyclic 3',5'-adenosine monophosphate [cAMP]) and nitric oxide content were determined. The antiischemic effect was characterized by change of intracavital ST segment.

RESULTS

Cicletanine treatment significantly decreased the incidence of ventricular arrhythmias, increased cardiac cGMP and nitric oxide content and reduced cardiac cAMP level. Cicletanine did not modify significantly QTc and Tpeak-Tend interval. The ST-segment change in response to rapid pacing was reduced significantly by CIC. (P < 0.05).

CONCLUSIONS

Cicletanine exerts beneficial cardiac effects in rabbits with symptoms of MS, which may be of influence with regard to the clinical application of the drug.

The use of drug metabolism for prediction of intestinal permeability (dagger)

The Biopharmaceutics Classification System (BCS), based on the aqueous solubility and intestinal permeability of a drug substance, has been widely used to predict the extent of drug absorption during the course of pharmaceutical development. Combined with product dissolution data, this system has gained a prominent role in regulatory process to determine if a drug formulated in an immediate release solid oral dosage form qualifies for waiver of in vivo bioequivalence studies. In parallel, the Biopharmaceutics Drug Disposition Classification System (BDDCS), using aqueous solubility and drug metabolism, takes on another venue to predict overall drug disposition. It has been suggested that the matrix of drug metabolism in BDDCS can be used to substantiate the classification of permeability by BCS. A total of 51 drugs were compiled in this study to examine the use of drug metabolism for predicting permeability. All compounds were classified as high permeability based on BCS, but only 73% of the compounds were found to exhibit extensive metabolism. Lipophilicity accounts for significant metabolism of many highly permeable drugs. Fourteen (14) out of 51 drugs have poor metabolism, suggesting that high permeability as defined by BCS does not necessarily dictate extensive metabolism. The drugs that have high permeability but poor metabolism are generally hydrophilic molecules with low molecular weight and are likely to be absorbed by active transport mechanisms. Based on the present data and literature information, it seems logical to predict that the extent of absorption is mostly complete (or > or =90%) if the drug is subject to a high degree of metabolism (e.g., > or =90%). The extent of drug metabolism may be useful in supporting permeability classification under certain circumstances.

Dose-response effects of sotalol on cardiovascular function in conscious, freely moving cynomolgus monkeys

BACKGROUND AND PURPOSE

The non-selective beta-adrenoceptor antagonist, D,L-sotalol (sotalol) is commonly employed as a positive control during preclinical cardiovascular safety pharmacology testing, mainly because of its ability to prolong QT interval duration. However, no information appears in the literature, except in abstract form, regarding the dose-response effects of sotalol in unanesthetized monkeys. The current study was conducted to determine the dose- and plasma-response effects of orally administered sotalol on cardiovascular function in conscious non-human primates.

EXPERIMENTAL APPROACH

Male cynomolgus monkeys were implanted with telemetry devices and the effects of sotalol hydrochloride (5, 10 and 30 mg kg(-1) of body weight, p.o.) on arterial blood pressure, heart rate, body temperature and electrocardiogram waveform were continuously monitored for 6 h after dosing. Blood was sampled for the measurement of plasma concentrations of sotalol.

KEY RESULTS

Sotalol dose dependently decreased heart rate and prolonged RR, PR, QT and corrected QT intervals, while having little or no effects on the QRS complex, arterial pressure or body temperature, over the dose range tested. When the data were related to plasma concentrations of sotalol, it was clear that the cardiovascular effects occurred in a similar pattern and to a comparable degree as those reported in human studies.

CONCLUSIONS AND IMPLICATIONS

The current study helps demonstrate the validity of utilizing telemetry-instrumented non-human primates for the cardiovascular safety pharmacology assessment of drugs prior to first-in-human testing, and its findings may serve as a reference source for the dose- and plasma-response effects of orally administered sotalol in conscious monkeys.

The Clinical Noncompliance of Oral Sotalol/Magnesium for Prophylactic Treatment of Atrial Fibrillation After Coronary Artery Bypass Grafting

BACKGROUND

Postoperative atrial fibrillation has been refractory to many attempted pharmacologic prevention methods and, when effective, side effects have been described. The present aim was to study the clinical compliance of a suggested prophylactic treatment, oral sotalol, and magnesium.

METHODS

Coronary-bypass patients without clinical contraindications to receive oral sotalol (80 mg twice daily) and magnesium supplementation were enrolled (n = 49) with an intention-to-treat strategy and being compared with a matched control group (n = 844). A protocol listed exclusion criteria of clinical compliance that was postoperatively evaluated prior to and during treatment.

RESULTS

Twenty-seven of the 49 enrolled patients (55%) were compliant to sustain the treatment according to the protocol. The remaining patients were postoperatively excluded, mainly because of hemodynamic reasons, of whom 14 were noncompliant to initiate any treatment. The AF occurrence in the compliant group was 7% versus 36% in noncompliant patients (p = 0.035), and 24% in the control group (p = 0.076). However, with an intention-to-treat policy the overall AF incidence became 18%. The subgroups of enrolled patients demonstrated skewing phenomena. The noncompliant group had higher requirement for inotropic support (p = 0.029) and longer aortic cross-clamp time (p = 0.048) compared to compliant patients. Further, the body weight of noncompliant patients was markedly lower than in the compliant counterpart (p = 0.015).

CONCLUSIONS

The tested treatment protocol showed limited compliance among routine cardiac-surgery patients, and further, introduced a biased selection of patients that skewed the results and may have partly explained the treatment effect.

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

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

QT PRODACT: Inter-facility Variability in Electrocardiographic and Hemodynamic Parameters in Conscious Dogs and Monkeys

In safety pharmacology studies, the effect of a test compound on the electrocardiogram is routinely examined by using conscious dogs. However, the results may be widely variable. The monkey, on the other hand, has scarcely been used for such studies; and as yet, there have not been reported studies on monkeys conducted at several facilities with a standard protocol. In the present study, we examined inter-facility variabilities in electrocardiographic and hemodynamic parameters as described below. We analyzed the data from 8 facilities (9 test groups) on dogs and 5 facilities (7 test groups) on monkeys. This data was obtained from the studies employing the following standard protocol: dl-Sotalol or a vehicle (0.5 w/v% methylcellulose solution) was given to animals; and the PR interval, QRS duration, QT interval, heart rate, and mean blood pressure were determined time-sequentially before and after administration of the vehicle or dl-sotalol in each test group. dl-Sotalol produced a prolongation of the maximum mean QTcF interval in conscious dogs and QTcB interval in conscious monkeys by more than 10% in every test group. No difference in the corrected QT interval among the test groups was observed in dogs, but a difference was observed in monkeys.

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.

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.

A review of class III antiarrhythmic agents for atrial fibrillation: maintenance of normal sinus rhythm

A noteworthy shift from class I to class III antiarrhythmic agents for suppression of atrial fibrillation has occurred. Sotalol, amiodarone, and dofetilide have been evaluated for their ability to maintain sinus rhythm in patients with chronic atrial fibrillation. All of these agents are moderately effective; however, amiodarone appears to be most efficacious. Aside from their common class III actions, these agents have profoundly different pharmacologic, pharmacokinetic, safety, and drug interaction profiles that help guide drug selection. Amiodarone and dofetilide are safe in patients who have had a myocardial infarction and those with heart failure. The safety of commercially available d,l-sotalol in these patients is poorly understood. Torsades de pointes is the most serious adverse effect of sotalol and dofetilide, and risk increases with renal dysfunction. Amiodarone has minimal proarrhythmic risk but has numerous noncardiac toxicities that require frequent monitoring. Overall, an ideal antiarrhythmic agent does not exist, and drug selection should be highly individualized.

Intravenous sotalol decreases transthoracic cardioversion energy requirement for chronic atrial fibrillation in humans: assessment of the electrophysiological effects by biatrial basket electrodes

OBJECTIVES

This study was undertaken to assess the effects of sotalol on the transthoracic cardioversion energy requirement for chronic atrial fibrillation (AF) and on the atrial electrograms during AF recorded by two basket electrodes.

BACKGROUND

The effects of sotalol infusion on transthoracic electrical cardioversion for chronic atrial fibrillation in humans have not been well investigated.

METHODS

We included 18 patients with persistent AF for more than three months. Atrial electrograms were recorded by two basket electrodes positioned in each atrium respectively. Transthoracic cardioversion was performed before and after sotalol 1.5 mg/kg i.v. infusion.

RESULTS

In the 14 patients whose AF could be terminated by cardioversion before sotalol infusion, the atrial defibrillation energy was significantly reduced after sotalol infusion (236 +/- 74 jules [J] vs. 186 +/- 77 J; p < 0.01). Atrial fibrillation was refractory to cardioversion in four patients at baseline and was converted to sinus rhythm by cardioversion after sotalol infusion in two of them. We further divided the patients into two groups. Group A consisted of 10 patients in whom the energy requirement was decreased by sotalol while group B consisted of eight patients in whom the energy requirement was not decreased. The mean A-A (atrial local electrogram) intervals during AF were significantly increased after sotalol infusion in both groups, but the increment of A-A interval was significantly larger in group A than it was in group B patients (36 +/- 13 ms vs. 22 +/- 8 ms for the right atrium; 19 +/- 7 ms vs. 9 +/- 7 ms for the left atrium; both p < 0.05). The spatial and temporal dispersions of A-A intervals were not significantly changed after sotalol infusion in both atria in both groups.

CONCLUSIONS

Sotalol decreases the atrial defibrillation energy requirement by increasing atrial refractoriness but not by decreasing the dispersion of refractoriness.

[Bioavailability of sotalol in short bowel syndrome]

BACKGROUND

The individual bioavailability of enterally administered drugs is usually uncertain in case of reduced bowel length. Routine measurements of plasma concentrations are available only for a small number of drugs. The daily dose recommended by the manufacturers may result in subtherapeutic plasma concentrations when given to such patients.

CASE REPORT

In 2 patients with hemodynamically relevant atrial fibrillation and reduced gut length application of increasing sotalol doses was initiated. For the assessment of the individual bioavailability plasma concentrations were measured via HPLC immediately before and 2 hours after enteral application of sotalol. Judging by clinical criteria both patients were treated successfully. Even in the patient with severe short bowel syndrome (stomach, duodenum and 50 cm jejunal remnant) doubling of the daily dose led to a substantial increase in plasma concentrations.

CONCLUSION

Effective enteral medication with sotalol in patients with short residual bowel is possible. Normal plasma concentrations can be achieved by administering doses according to the manufacturers' instructions. In case of severe short bowel syndrome, the measurements of plasma concentrations may be beneficial in supervising dose-adjustment.

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.

Maintenance of sinus rhythm with oral d,l-sotalol therapy in patients with symptomatic atrial fibrillation and/or atrial flutter. d,l-Sotalol Atrial Fibrillation/Flutter Study Group

Currently d,l-sotalol is widely used to prevent recurrence of atrial fibrillation and/or atrial flutter, although a randomized dose-response study has not previously been conducted to guide therapy for this indication. This study summarizes findings of a double-blind, placebo-controlled, multicenter, randomized trial evaluating the efficacy, safety, and dose-response relation of 3 fixed doses of d,l-sotalol (80, 120, and 160 mg twice daily) for the maintenance of sinus rhythm in 253 patients with atrial fibrillation and/or atrial flutter. All patients were in sinus rhythm at randomization. Treatment (69 patients on placebo, 59 on 80 mg, 63 on 120 mg, and 62 on 160 mg given twice daily) was continued for 12 months or until documented recurrence of symptomatic atrial fibrillation and/or flutter. Transtelephonic electrocardiographic monitoring was used to detect symptomatic recurrences. Demographic characteristics were not different in the 4 groups. Structural heart disease was present in 57% of patients. Patients with a history of heart failure were excluded. The time from randomization to symptomatic arrhythmia recurrence was significantly longer in the 2 higher d,l-sotalol dose groups than in the placebo group. The median times to recurrence were 27, 106, 229, and 175 days for the placebo, 80, 120, and 160 mg groups, respectively. There were no deaths or cases of torsade de pointes, sustained ventricular tachycardia, or ventricular fibrillation reported. Thus, d,l-sotalol appeared to be both safe and effective in maintaining sinus rhythm in patients with symptomatic atrial fibrillation and/or flutter. Further, the 120-mg twice daily dose appeared to provide the most favorable benefit and/or risk.

Sotalol: An important new antiarrhythmic

Sotalol, the most recently approved oral antiarrhythmic drug, has a unique pharmacologic profile. Its electrophysiology is explained by nonselective beta-blocking action as well as class III antiarrhythmic activity (including fast-activating cardiac membrane-delayed rectifier current blockade), which leads to increases in action potential duration and refractory period throughout the heart and in QT interval on the surface electrocardiogram. Its better hemodynamic tolerance than other beta-blockers may be a result of enhanced inotropy associated with class III activity. Sotalol's ability to suppress ventricular ectopy is similar to that of class I agents and better than that of standard beta-blockers. Unlike class I agents, its use in a postinfarction trial was not associated with increased mortality rate. Therapeutically, it has shown superior efficacy for prevention of recurrent ventricular tachycardia and ventricular fibrillation, which was the basis for its approval. In a randomized study, the Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial, sotalol was associated with an increased in-hospital efficacy prediction rate (by Holter monitor or electrophysiologic study), reduced long-term arrhythmic recurrence rate with superior tolerance, and lower mortality rate than class I ("standard") antiarrhythmic drugs. Sotalol was 1 of 2 drugs selected for comparison with implantable defibrillators in the recent National Institutes of Health Antiarrhythmics versus Implantable Defibrillator (AVID) study. Sotalol appears to be a preferred drug for use with implantable defibrillators; unlike some other agents (eg, amiodarone) it does not elevate and, indeed, may lower defibrillation threshold. Although unapproved for this use, sotalol is active against atrial arrhythmias. It has shown efficacy equivalent to propafenone and quinidine in preventing atrial fibrillation recurrence, but it is better tolerated than quinidine and provides excellent rate control during recurrence. Sotalol's major side effects are related to beta-blockade and the risk of torsades de pointes (acceptably small if appropriate precautions are taken). Unlike several other antiarrhythmics (eg, amiodarone), it has no pharmacokinetic drug-drug interactions, is not metabolized, and is entirely renally excreted. Initial dose is 80 mg twice daily, with gradual titration to 240 to 360 mg/day as needed. The daily dose must be reduced in renal failure. On the basis of favorable clinical trials and practice experience, sotalol has shown a steadily growing impact on the treatment of arrhythmias during its 5 years of market availability, a trend that is likely to continue.

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.

Pharmacologic and pharmacokinetic profile of class III antiarrhythmic drugs

Cardiac arrhythmias frequently respond only to drugs that have as their predominant electrophysiologic effect the prolongation of repolarization and refractoriness. According to the Singh-Vaughan Williams classification, these drugs are known as class III agents. In the last few years, interest has increased in the development of class III antiarrhythmic drugs as alternatives to sodium channel blocking agents, which mainly affect cardiac conduction. Much of this interest results from a perceived danger of using drugs with sodium channel blocking properties, particularly in patients with ischemic heart disease, based on the results of the Cardiac Arrhythmia Suppression Trial (CAST) and several other trials. This article is a review of the pharmacology, including the pharmacokinetics and pharmacodynamics, of the most commonly used and investigated class III antiarrhythmic drugs. As will be seen from the discussion, each of these drugs has novel pharmacology that makes it applicable in specific clinical situations. Their putative effects on various arrhythmogenic mechanisms and their efficacy in treating specific target arrhythmias will be addressed.

Sotalol Is More Powerful Than Propranolol in Suppressing Complex Ventricular Arrhythmias

BACKGROUND: Sotalol has combined type II and type III antiarrhythmic properties. Although the beta-blocking action of sotalol is thought to contribute to its antiarrhythmic actions, few data are available from direct comparative clinical trials with pure beta-blocking drugs. METHODS AND RESULTS: In this double-blind, randomized, multicenter, placebo-controlled, parallel study, we have compared the antiarrhythmic efficacy and safety of treatment with sotalol vs propranolol in 181 patients with organic heart disease and frequent (>30 ventricular premature complexes [VPCs]/h) repetitive ventricular premature complexes. Eighty-seven were randomized to receive sotalol and 94 received propranolol. The demographic and clinical characteristics of the two groups were identical, and the majority of patients had coronary artery disease or hypertensive heart disease. Most patients had a long-standing history (>5 years) of ventricular arrhythmias and, in a significant proportion, antiarrhythmic therapy with other drugs had failed in the past. After withdrawal of all antiarrhythmic drugs and 1 week of placebo, qualified patients were randomized to sotalol (320 mg/day) or propranolol (120 mg/day). patients not achieving adequate response were given higher doses of sotalol (640 mg/day) or propranolol (240 mg/day)At baseline, both groups had comparable frequency of total VPCs/hour (274/h and 255/h for sotalol and propranolol groups, respectively) which was reduced to 71 VPCs/h and 109/VPCs/h, respectively, at the end of phase 1. At final evaluation there was a significantly greater response to sotalol as demonstrated by 80% reduction in VPCs/hour with sotalol compared with only 50% reduction noted in the propranolol group. Adequate therapeutic response was also achieved in a significantly greater percentage of patients on sotalol compared with propranolol (56% vs 29%, P =.02). Sotalol was also superior to propranolol in suppressing the VT events/day during phase 1 (89% vs 78% reduction in VT events/day, P <.05). Sotalol was more effective than propranolol in all subgroups and in patients with heart rate <75 beats per minute. CONCLUSIONS: Sotalol is more powerful than propranolol in suppressing ventricular arrhythmias documented on Holter recordings. The superiority of sotalol appears to be related to its combined class II and class III antiarrhythmic actions.

Sematilide blocks the inward rectifier potassium channel in isolated guinea pig ventricular myocytes

1. In whole-cell patch recording, the relative potency of the blocking action of sematilide on IK1 was found to be constant at each potential level of IK1 activation. Under more acidic condition, the degree of block was decreased. These results strongly suggested that the neutral form of sematilide may penetrate the cardiac cell membrane via hydrophobic pathway. 2. In cell-attached patches, sematilide prolonged the interburst interval and reduced the opening probabilities of the IK1 channel without affecting either the mean open time or the mean closed time within a burst.

Transport approaches to the biopharmaceutical design of oral drug delivery systems: prediction of intestinal absorption

For almost a half century scientists have striven to develop a theoretical model capable of predicting oral drug absorption in humans. From the pH-partition hypothesis to the compartmental absorption and transit (CAT) model, various qualitative/quantitative approaches have been proposed, revised and extended. In this review, these models are classified into three categories; quasi-equilibrium models, steady-state models and dynamic models. The quasi-equilibrium models include the pH-partition hypothesis and the absorption potential concept, the steady-state models include the film model and the mass balance approaches, and the dynamic models include the dispersion, mixing tank and CAT models. The quasi-equilibrium models generally provide a basic guideline for understanding drug absorption trends. The steady-state models can be used to estimate the fraction of dose absorbed. The dynamic models predict both the fraction of dose absorbed and the rate of drug absorption and can be related to pharmacokinetic models to evaluate plasma concentration profiles.

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

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

Sotalol proarrhythmia: a report of five cases and an audit of the use of a sotalol in a teaching hospital

BACKGROUND

Polymorphic ventricular tachycardia is an uncommon complication of sotalol use.

AIMS

The aims of this study were: (1) to report five cases of sotalol proarrhythmia and (2) to audit the use of sotalol in a teaching hospital population.

METHODS

Five patients with sotalol proarrhythmia (defined as new ventricular arrhythmias associated with sotalol administration) were identified over an 18 month period. Sotalol use for patients admitted to the John Hunter Hospital was audited over a six month period with 85 patients (55 males) identified from the pharmacy database. Medical records were reviewed and the details of treatment including sotalol dose and indication determined. Creatinine clearance was estimated by the Cockcroft and Gault regression equation.

RESULTS

The audit indicated that sotalol was prescribed predominantly for management of atrial arrhythmias (80%). Paroxysmal atrial fibrillation was the most common indication (71%). Although female patients were older (72 +/- 13 vs 62 +/- 15 years, p < 0.001) and had a lower creatinine clearance (55 +/- = 24 vs 82 +/- = 32 mg/minute, p < 0.001) than male patients, they were prescribed similar doses of sotalol (206 +/- 112 vs 193 +/- 93 mg/day). The ratio of sotalol dose to creatinine clearance was higher in female patients (4.0 +/- 2.6 vs 2.16 +/- 1.5, p < 0.01). The five patients with proarrhythmia (torsades de pointes in four patients and polymorphic ventricular tachycardia in one patient) were all female. Daily sotalol dose (odds ratio for each 160 mg tablet 4.9 [95% confidence interval 1.5-16] and female gender (p < 0.01) were significant risk factors for proarrhythmia.

CONCLUSION

Sotalol dose was not appropriately adjusted for creatinine clearance which is age and gender dependent. Female patients have an increased risk of proarrhythmia and should receive lower doses of sotalol.

The protective effect of D-sotalol against hypoxia-induced myocardial uncoupling

The effects of D-sotalol on intercellular electrical coupling and ultrastructure under hypoxic conditions were investigated in myocardial samples from eight young (1-2 months) and four older (10-12 months) guinea pigs. A right ventricular muscle strip was kept simultaneously in two divided chambers and superfused with normoxic and/or hypoxic (97% N2+ 3% Co2) Krebs solution. Hypoxia caused shortening of action potential duration (APD) and electrical cell-to-cell uncoupling. If the uncoupling appeared after short-term hypoxia (less than 30 min), administration of 3.10(-7)M of D-sotalol to the hypoxic perfusate led to a recovery of electrical coupling. Transmission electron microscopy revealed moderate reversible ultrastructural alterations of the cardiomyocytes. No apparent changes in intercellular junctions were observed. The recoupling effect of sotalol decreased with the time of hypoxia as the ultrastructural damage progressed. After prolonged hypoxia (more than 30 min), cardiomyocytes were markedly injured, intercellular junctions were severely affected, and gap junctions occurred less frequently. In these cases, administration of D-sotalol caused only transient recoupling. After 1 h of hypoxia, no recoupling was observed. Pretreatment with D-sotalol prevented hypoxia-induced electrical uncoupling and markedly attenuated ultrastructural damage, although shortening of APD still persisted. Our results indicate that the cardioprotective effect of D-sotalol on electrical intercellular coupling is closely associated with sotalol-induced prevention of the ultrastructural damage. Considering previous results, we suggest that this protective effect of D-sotalol may be related to its ability to increase intracellular cyclic adenosine monophosphate and, thereby, to decrease cytosolic free Ca. These effects can explain the antiarrhythmic and defibrillating properties of D-sotalol.

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.

Enantioselective analysis of sotalol in plasma by reversed-phase high-performance liquid chromatography using diastereomeric derivatives

A procedure for the concurrent determination of the (+)- and (-)-enantiomers of sotalol in plasma using high-performance liquid chromatography of diastereomeric derivatives is described. Sotalol is extracted from a 0.5-ml aliquot of plasma at pH 9.3 using ethyl acetate. Atenolol is used as the internal standard. The ethyl acetate is removed under vacuum, and the residue derivatized with R-(-)-1-(1-naphthyl)ethyl isocyanate (NEIC, 0.005% in chloroform) in the presence of trace quantities of carbonate buffer. The chloroform is removed, the residue reconstituted in mobile phase (acetonitrile-water, 39:61, v/v), and an aliquot injected into the HPLC column. A C18 trapping column is used to retain excess derivatizing reagent. While the derivatives are separated on a C18 analytical column with the isocratic mobile phase mentioned above at 1.5 ml/min, the column-switching allows back-flushing of the trapping column to prepare for the next injection. The derivatives were detected using a fluorescence detector with excitation wavelength 280 nm and emission wavelength 320 nm. The method was fully validated, and shown to have excellent linearity, specificity, sensitivity, accuracy and precision. It has been applied to the determination of (+)- and (-)-sotalol in plasma from twelve subjects dosed with racemic sotalol.

Sotalol for refractory arrhythmias in pediatric and young adult patients: initial efficacy and long-term outcome

Sotalol is an antiarrhythmic medication that has properties of both a beta-blocker and a class III agent and has been used safely and effectively to treat arrhythmias of multiple mechanisms in pediatric patients. The purpose of this study was to review our institutional experience with sotalol in 45 patients with refractory arrhythmias and determine their long-term outcome. Patients responded to sotalol with 80% efficacy and a 22% incidence of adverse side effects. The mean sotalol dose was 116 mg/m2/day, and the average duration of therapy was 15.2 months. In spite of 80% efficacy, only 22% of patients remained on sotalol long-term. Sotalol was discontinued most commonly for either spontaneous resolution of disease or definitive cure by radiofrequency ablation. Other reasons for discontinuation of effective therapy included adverse side effects and arrhythmia control with either an antitachycardia pacemaker or another medication. One patient died while taking sotalol, but this case was considered a failure of treatment rather than an adverse side effect. Of the patients who still receive therapy, several have complex structural heart disease and require a combination of therapies, including sotalol, for adequate rhythm control.

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.

Sotalol: from "just another beta blocker" to "the prototype of class III antidysrhythmic compound"

Sotalol is a beta-blocking drug devoid of membrane stabilizing properties, as well as intrinsic sympathomimetic actions, or cardioselectivity. In addition, sotalol prolongs atrial and ventricular repolarization (Class III antiarrhythmic activity). It appears to have less myocardial depressant effect than other beta-blocking agents. Given orally, bioavailability of the drug reaches 100%. Sotalol's plasma half-life is 15 hours (range 7-18) and is dependent only on renal function. In clinical practice, it has been found effective in the suppression of nearly all supraventricular and ventricular dysrhythmias except those related to prolonged ventricular repolarization. Most common adverse effects are dyspnea, bradycardia, and fatigue, which results in drug termination in 16% of the cases. Torsades de pointes usually associated with bradycardia and drug induced QTc prolongation has been reported in 1.9%-3.5% of the patients receiving sotalol. This complication may be reduced by limiting the dose (< 640 mg/day) especially in patients with impaired renal function. In addition hypokalemia must be avoided. To sum up, the combination of Class II and Class III effects may carry additional benefits. However, further studies are required to test such hypotheses.

Sotalol

Sotalol is a novel antiarrhythmic agent combining beta-adrenergic-antagonist actions with the ability to increase cardiac repolarization and refractoriness. The drug's electrophysiologic and clinical profile is different from that of conventional beta-receptor antagonists. As compared with other antiarrhythmic agents, sotalol prevents recurrences of arrhythmia in a higher proportion of patients, particularly among those presenting with ventricular tachycardia and aborted sudden cardiac death. The net hemodynamic effect of sotalol is the result of a balance between the depressant effects due to beta-receptor blockade and an action that tends to increase contractility. Although initially marketed in the United States for treatment of life-threatening ventricular arrhythmias, sotalol also has demonstrated efficacy in many patients with supraventricular arrhythmias. As with all drugs that prolong the QT interval, the syndrome of torsade de pointes is a serious potential adverse effect.

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.