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Mechanism Of Action
Sotalol has both beta-adrenoreceptor blocking (Vaughan Williams Class II) and cardiac action potential duration prolongation (Vaughan Williams Class III) antiarrhythmic properties. The two isomers of sotalol have similar Class III antiarrhythmic effects, while the l-isomer is responsible for virtually all of the beta-blocking activity. The beta-blocking effect of sotalol is non-cardioselective, half maximal at about 80 mg/day and maximal at doses between 320 and 640 mg/day. Sotalol does not have partial agonist or membrane stabilizing activity. Although significant beta-blockade occurs at oral doses as low as 25 mg, significant Class III effects are seen only at daily doses of 160 mg and above.
In children, a Class III electrophysiologic effect can be seen at daily doses of 210 mg/m² body surface area (BSA). A reduction of the resting heart rate due to the beta-blocking effect of sotalol is observed at daily doses ≥ 90 mg/m² in children.
Cardiac Electrophysiological Effects
Sotalol hydrochloride prolongs the plateau phase of the cardiac action potential in the isolated myocyte, as well as in isolated tissue preparations of ventricular or atrial muscle (Class III activity). In intact animals it slows heart rate, decreases AV nodal conduction and increases the refractory periods of atrial and ventricular muscle and conduction tissue.
In man, the Class II (beta-blockade) electrophysiological effects of sotalol are manifested by increased sinus cycle length (slowed heart rate), decreased AV nodal conduction and increased AV nodal refractoriness. The Class III electrophysiological effects in man include prolongation of the atrial and ventricular monophasic action potentials, and effective refractory period prolongation of atrial muscle, ventricular muscle, and atrioventricular accessory pathways (where present) in both the anterograde and retrograde directions. With oral doses of 160 to 640 mg/day, the surface ECG shows dose-related mean increases of 40–100 msec in QT and 10–40 msec in QTc [See WARNINGS AND PRECAUTIONS]. No significant alteration in QRS interval is observed.
In a small study (n=25) of patients with implanted defibrillators treated concurrently with Betapace, the average defibrillatory threshold was 6 joules (range 2–15 joules) compared to a mean of 16 joules for a nonrandomized comparative group primarily receiving amiodarone.
Twenty-five children in an unblinded, multicenter trial with SVT and/or ventricular tachyarrhythmias, aged between 3 days and 12 years (mostly neonates and infants), received an ascending titration regimen with daily doses of 30, 90 and 210 mg/m² with dosing every 8 hours for a total 9 doses. During steady-state, the respective average increases above baseline of the QTc interval were 2, 14, and 29 msec at the 3 dose levels. The respective mean maximum increases above baseline of the QTc interval were 23, 36, and 55 msec at the 3 dose levels. The steady-state percent increases in the RR interval were 3, 9 and 12%. The smallest children (BSA < 0.33 m²) showed a tendency for larger Class III effects (ΔQTc) and an increased frequency of prolongations of the QTc interval as compared with larger children (BSA ≥ 0.33 m²). The beta-blocking effects also tended to be greater in the smaller children (BSA < 0.33 m²). Both the Class III and beta-blocking effects of sotalol were linearly related to the plasma concentrations.
In a study of systemic hemodynamic function measured invasively in 12 patients with a mean LV ejection fraction of 37% and ventricular tachycardia (9 sustained and 3 non-sustained), a median dose of 160 mg twice daily of Betapace produced a 28% reduction in heart rate and a 24% decrease in cardiac index at 2 hours post-dosing at steady-state. Concurrently, systemic vascular resistance and stroke volume showed nonsignificant increases of 25% and 8%, respectively. One patient was discontinued because of worsening congestive heart failure. Pulmonary capillary wedge pressure increased significantly from 6.4 mmHg to 11.8 mmHg in the 11 patients who completed the study. Mean arterial pressure, mean pulmonary artery pressure and stroke work index did not significantly change. Exercise and isoproterenol induced tachycardia are antagonized by Betapace, and total peripheral resistance increases by a small amount.
In hypertensive patients, sotalol produces significant reductions in both systolic and diastolic blood pressures. Although sotalol is usually well-tolerated hemodynamically, deterioration in cardiac performance may occur in patients with marginal cardiac compensation [see WARNINGS AND PRECAUTIONS].
The pharmacokinetics of the d and l enantiomers of sotalol are essentially identical.
In healthy subjects, the oral bioavailability of sotalol is 90–100%. After oral administration, peak plasma concentrations are reached in 2.5 to 4 hours, and steady-state plasma concentrations are attained within 2–3 days (that is, after 5–6 doses when administered twice daily). Over the dosage range 160–640 mg/day sotalol displays dose proportionality with respect to plasma concentrations. When administered with a standard meal, the absorption of sotalol was reduced by approximately 20% compared to administration in fasting state.
Sotalol does not bind to plasma proteins. Distribution occurs to a central (plasma) and to a peripheral compartment. Sotalol crosses the blood brain barrier poorly.
Sotalol is not metabolized and is not expected to inhibit or induce any CYP450 enzymes.
Excretion of sotalol is predominantly via the kidney in the unchanged form, and therefore lower doses are necessary in conditions of renal impairment [see DOSAGE AND ADMINISTRATION]. The mean elimination half-life of sotalol is 12 hours. Dosing every 12 hours results in trough plasma concentrations which are approximately one-half of those at peak.
Pediatric: The combined analysis of a single-dose study and a multiple-dose study with 59 children, aged between 3 days and 12 years, showed the pharmacokinetics of sotalol to be first order. A daily dose of 30 mg/m² of sotalol was administered in the single dose study and daily doses of 30, 90 and 210 mg/m² were administered every 8 hours in the multi-dose study. After rapid absorption with peak levels occurring on average between 2–3 hours following administration, sotalol was eliminated with a mean half-life of 9.5 hours. Steady-state was reached after 1–2 days. The average peak to trough concentration ratio was 2. BSA was the most important covariate and more relevant than age for the pharmacokinetics of sotalol. The smallest children (BSA < 0.33m²) exhibited a greater drug exposure (+59%) than the larger children who showed a uniform drug concentration profile. The intersubject variation for oral clearance was 22%.
Geriatric: Age does not significantly alter the pharmacokinetics of Betapace/Betapace AF, but impaired renal function in geriatric patients can increase the terminal elimination half-life, resulting in increased drug accumulation.
Renal Impairment: Sotalol is mainly eliminated via the kidneys through glomerular filtration and to a small degree by tubular secretion. There is a direct relationship between renal function, as measured by serum creatinine or creatinine clearance, and the elimination rate of sotalol. The half-life of sotalol is prolonged (up to 69 hours) in anuric patients. Doses or dosing intervals should be adjusted based on creatinine clearance [see DOSAGE AND ADMINISTRATION].
Hepatic Impairment: Patients with hepatic impairment show no alteration in clearance of sotalol.
Antacids: Administration of oral sotalol within 2 hours of antacids may result in a reduction in Cmax and AUC of 26% and 20%, respectively, and consequently in a 25% reduction in the bradycardic effect at rest. Administration of the antacid two hours after oral sotalol has no effect on the pharmacokinetics or pharmacodynamics of sotalol.
No pharmacokinetic interactions were observed with hydrochlorothiazide or warfarin.
Betapace (sotalol hydrochloride) has been studied in life-threatening and less severe arrhythmias. In patients with frequent premature ventricular complexes (VPC), Betapace (sotalol hydrochloride) was significantly superior to placebo in reducing VPCs, paired VPCs and non-sustained ventricular tachycardia (NSVT); the response was dose-related through 640 mg/day with 80–85% of patients having at least a 75% reduction of VPCs. Betapace was also superior, at the doses evaluated, to propranolol (40–80 mg TID) and similar to quinidine (200–400 mg QID) in reducing VPCs. In patients with life-threatening arrhythmias [sustained ventricular tachycardia/fibrillation (VT/VF)], Betapace was studied acutely [by suppression of programmed electrical stimulation (PES) induced VT and by suppression of Holter monitor evidence of sustained VT] and, in acute responders, chronically.
In a double-blind, randomized comparison of Betapace and procainamide given intravenously (total of 2 mg/kg Betapace vs. 19 mg/kg of procainamide over 90 minutes), Betapace suppressed PES induction in 30% of patients vs. 20% for procainamide (p=0.2).
In a randomized clinical trial [Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) Trial] comparing choice of antiarrhythmic therapy by PES suppression vs. Holter monitor selection (in each case followed by treadmill exercise testing) in patients with a history of sustained VT/VF who were also inducible by PES, the effectiveness acutely and chronically of Betapace was compared with that of 6 other drugs (procainamide, quinidine, mexiletine, propafenone, imipramine and pirmenol). Overall response, limited to first randomized drug, was 39% for Betapace and 30% for the pooled other drugs. Acute response rate for first drug randomized using suppression of PES induction was 36% for Betapace vs. a mean of 13% for the other drugs. Using the Holter monitoring endpoint (complete suppression of sustained VT, 90% suppression of NSVT, 80% suppression of VPC pairs, and at least 70% suppression of VPCs), Betapace yielded 41% response vs. 45% for the other drugs combined. Among responders placed on long-term therapy identified acutely as effective (by either PES or Holter), Betapace, when compared to the pool of other drugs, had the lowest two-year mortality (13% vs. 22%), the lowest two-year VT recurrence rate (30% vs. 60%), and the lowest withdrawal rate (38% vs. about 75–80%). The most commonly used doses of Betapace in this trial were 320– 480 mg/day (66% of patients), with 16% receiving 240 mg/day or less and 18% receiving 640 mg or more.
It cannot be determined, however, in the absence of a controlled comparison of Betapace vs. no pharmacologic treatment (for example, in patients with implanted defibrillators) whether Betapace response causes improved survival or identifies a population with a good prognosis.
Betapace has not been shown to enhance survival in patients with ventricular arrhythmias.
Clinical Studies In Supra-ventricular Arrhythmias
Betapace AF has been studied in patients with symptomatic AFIB/AFL in two principal studies, one in patients with primarily paroxysmal AFIB/AFL, the other in patients with primarily chronic AFIB.
In one study, a U.S. multicenter, randomized, placebo-controlled, double-blind, dose-response trial of patients with symptomatic primarily paroxysmal AFIB/AFL, three fixed dose levels of Betapace AF (80 mg, 120 mg and 160 mg) twice daily and placebo were compared in 253 patients. In patients with reduced creatinine clearance (40-60 mL/min) the same doses were given once daily. Patients were excluded for the following reasons: QT > 450 msec; creatinine clearance < 40 mL/min; intolerance to beta-blockers; bradycardia-tachycardia syndrome in the absence of an implanted pacemaker; AFIB/AFL was asymptomatic or was associated with syncope, embolic CVA or TIA; acute myocardial infarction within the previous 2 months; congestive heart failure; bronchial asthma or other contraindications to beta-blocker therapy; receiving potassium losing diuretics without potassium replacement or without concurrent use of ACE-inhibitors; uncorrected hypokalemia (serum potassium < 3.5 meq/L) or hypomagnesemia (serum magnesium < 1.5 meq/L); received chronic oral amiodarone therapy for > 1 month within previous 12 weeks; congenital or acquired long QT syndromes; history of Torsade de Pointes with other antiarrhythmic agents which increase the duration of ventricular repolarization; sinus rate < 50 bpm during waking hours; unstable angina pectoris; receiving treatment with other drugs that prolong the QT interval; and AFIB/AFL associated with the Wolff-Parkinson-White (WPW) syndrome. If the QT interval increased to ≥ 520 msec (or JT ≥ 430 msec if QRS > 100 msec) the drug was discontinued. The patient population in this trial was 64% male, and the mean age was 62 years. No structural heart disease was present in 43% of the patients. Doses were administered once daily in 20% of the patients because of reduced creatinine clearance.
Betapace AF was shown to prolong the time to the first symptomatic, ECG-documented recurrence of AFIB/AFL, as well as to reduce the risk of such recurrence at both 6 and 12 months. The 120 mg dose was more effective than 80 mg, but 160 mg did not appear to have an added benefit. Note that these doses were given twice or once daily, depending on renal function. The results are shown in Figure 2, Table 7 and Table 8.
Figure 2: Study 1 – Time to First ECG-Documented
Recurrence of Symptomatic AFIB/AFL Since Randomization
Table 7: Study 1 – Patient
Status at 12 Months
|Placebo||Betapace AF Dose|
|80 mg||120 mg||160 mg|
|On treatment in NSR at 12 months without recurrencea||23%||22%||29%||23%|
|D/C for AEs||6%||12%||18%||29%|
|a Symptomatic AFIB/AFL
b Efficacy endpoint of Study 1; study treatment stopped.
Note that columns do not add up to 100% due to discontinuations (D/C) for “other” reasons.
Table 8: Study 1 – Median
Time to Recurrence of Symptomatic AFIB/AFL and Relative Risk (vs. Placebo) at
|Betapace AF Dose|
|P-value vs. placebo||0.325||0.018||0.029|
|Relative Risk (RR) to placebo||0.81||0.59||0.59|
|Median time to recurrence (days)||27||106||229||175|
Discontinuation because of adverse events was dose related.
In a second multicenter, randomized, placebo-controlled, double-blind study of 6 months duration in 232 patients with chronic AFIB, Betapace AF was titrated over a dose range from 80 mg/day to 320 mg/day. The patient population of this trial was 70% male with a mean age of 65 years. Structural heart disease was present in 49% of the patients. All patients had chronic AFIB for > 2 weeks but < 1 year at entry with a mean duration of 4.1 months. Patients were excluded if they had significant electrolyte imbalance, QTc > 460 msec, QRS > 140 msec, any degree of AV block or functioning pacemaker, uncompensated cardiac failure, asthma, significant renal disease (estimated creatinine clearance < 50 mL/min), heart rate < 50 bpm, myocardial infarction or open heart surgery in past 2 months, unstable angina, infective endocarditis, active pericarditis or myocarditis, ≥ 3 DC cardioversions in the past, medications that prolonged QT interval, and previous amiodarone treatment. After successful cardioversion patients were randomized to receive placebo (n=114) or Betapace AF (n=118), at a starting dose of 80 mg twice daily. If the initial dose was not tolerated it was decreased to 80 mg once daily, but if it was tolerated it was increased to 160 mg twice daily. During the maintenance period 67% of treated patients received a dose of 160 mg twice daily, and the remainder received doses of 80 mg once daily (17%) and 80 mg twice daily (16%).
Tables 9 and 10 show the results of the trial. There was a longer time to ECG-documented recurrence of AFIB and a reduced risk of recurrence at 6 months compared to placebo.
Table 9: Study 2 – Patient
Status at 6 Months
|On treatment in NSR at 6 months without recurrencea||29%||45%|
|D/C for AEs||3%||6%|
|a Symptomatic or asymptomatic AFIB/AFL
b Efficacy endpoint of Study 2; study treatment stopped.
Table 10: Study 2 – Median Time to Recurrence of
Symptomatic AFIB/AFL/Death and Relative Risk (vs. Placebo) at 6 Months
|P-value vs. placebo||0.002|
|Relative Risk (RR) to placebo||0.55|
|Median time to recurrence (days)||44||> 180|
Figure 3: Study 2 – Time to
First ECG-Documented Recurrence of Symptomatic AFIB/AFL/Death Since
Clinical Studies In Patients With Myocardial Infarction
In a large double-blind, placebo controlled secondary prevention (postinfarction) trial (n=1,456); Betapace (sotalol hydrochloride) was given as a non-titrated initial dose of 320 mg once daily. Betapace did not produce a significant increase in survival (7.3% mortality on Betapace vs. 8.9% on placebo, p=0.3), but overall did not suggest an adverse effect on survival. There was, however, a suggestion of an early (i.e., first 10 days) excess mortality (3% on Betapace vs. 2% on placebo).
In a second small trial (n=17 randomized to Betapace) where Betapace was administered at high doses (for example, 320 mg twice daily) to high-risk post-infarction patients (ejection fraction < 40% and either > 10 VPC/hr or VT on Holter), there were 4 fatalities and 3 serious hemodynamic/electrical adverse events within two weeks of initiating Betapace.
Last reviewed on RxList: 5/23/2016
This monograph has been modified to include the generic and brand name in many instances.
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