Efficacy and proarrhythmia of oral sotalol in pediatric patients

Population pharmacokinetics and pharmacodynamics of sotalol in pediatric patients with supraventricular or ventricular tachyarrhythmia

AIMS

To derive useful pharmacokinetic (PK) and pharmacodynamic (PD) information for guiding the clinical use of sotalol in pediatric patients with supraventricular (SVT) or ventricular tachyarrhythmia (VT).

METHODS

Two studies were conducted in-patients with SVT or VT in the age range between birth and 12 years old. Both studies used an extemporaneously compounded formulation prepared from sotalol HCl tablets. In the PK study, following a single dose of 30 mg/m2 sotalol, extensive blood samples (n = 10) were taken. The PK-PD study used a dose escalation design with doses of 10, 30, and 70 mg/m2, each administered three times at 8-hr intervals without a washout. Six ECG recordings for determination of QT and RR were obtained prior to the initial dose of sotalol. Four blood samples were collected six ECG's were determined during the third interval at each dose level. Plasma concentrations of sotalol (C) were assayed by LC/MS/MS. The data analysis used NONMEM to obtain the population PK and PD parameter estimates. The individual PK and PD parameters were estimated with empirical Bayes methodology.

RESULTS

A total of 611 C from 58 patients, 477 QTc and 499 RR measurements from 23 and 22 patients, respectively, were available for analysis. The PK of sotalol was best described by a linear two-compartment model. Oral clearance (CL/F) and volume of central compartment (Vc/F) were linearly correlated with body surface area (BSA), body weight or age. CL/F was also linearly correlated with creatinine clearance. The best predictor for both CL/F and Vc/F was BSA. The remaining intersubject coefficients of variation (CV's) in CL/F, and Vc/F were 21.6% and 20.3%, respectively. The relationship of QTc to C was adequately described by a linear model. The intersubject CV's in slope (SL) and intercept (E0) were 56.2 and 4.7%, respectively. The relationship of RR to C was also adequately described by a linear model in which the baseline RR and SL were related to age or BSA. The intersubject CV's for SL and E0 were 86.7 and 14.4%, respectively.

CONCLUSIONS

BSA is the best predictor for the PK of sotalol. Both QTc and RR effects are linearly related to C. No covariates are found for the QTc-C relation, while the RR-C relation shows age or BSA dependency.

Sinus node dysfunction and atrial tachycardia after the Fontan procedure: The scope of the problem

Similar to other atrial baffling procedures, the Fontan procedure exposes patients to ongoing morbidity and mortality. The development of the bradycardia-tachycardia syndrome can have adverse effects on already-marginal hemodynamics and ventricular function. Patients with Fontan physiology and sinus node dysfunction can be managed with antibradycardic pacemakers. Atrial arrhythmias after "completion Fontan" are difficult to treat and usually require either antiarrhythmic agents, antitachycardic pacemakers, or radiofrequency catheter ablation of the re-entrant circuit. Successful treatment of atrial flutter occurs in only 50% to 70% of patients. There is a high recurrence rate of atrial flutter with any of the accepted management strategies. Copyright 1998 by W.B. Saunders Company

Early postoperative arrhythmias after open-heart procedures in children with congenital heart disease

OBJECTIVE: Evaluation of occurrence, clinical course, necessity of treatment, and outcome of early postoperative cardiac arrhythmias after open-heart surgery. DESIGN: Prospective study. SETTING: Tertiary pediatric intensive care and pediatric cardiology unit. PATIENTS: All consecutive pediatric patients undergoing cardiac surgery on cardiopulmonary bypass were studied for the occurrence of cardiac arrhythmias during the whole perioperative hospital stay. Measurements: All patients had continuous electrocardiographic monitoring (with memory function) during the whole intensive care stay. A 24-hr Holter recording was done thereafter in patients with arrhythmias. RESULTS: Of 310 patients studied, 83 (27%) had postoperative arrhythmias. The occurrence rate was not different whether surgical access was by atriotomy or ventriculotomy (26% vs. 28%, respectively). Infants (39%) and cyanotic patients (36%) had a higher occurrence rate of arrhythmias (p <.05). Arrhythmias were more common after prolonged cardiopulmonary bypass time and with higher postoperative maximum troponin serum levels. In addition, patients with hemodynamically significant residual findings after correction had an increased occurrence rate of arrhythmias (18 of 43; 42%; p <.01). Of the 83 children with arrhythmias, 53 (64%) required specific antiarrhythmic treatment. The use of antiarrhythmic drugs was required in only 7 of these patients. Only one patient (1.2% of patients with arrhythmias) died from arrhythmia. No major complications resulting from arrhythmias occurred during the postoperative clinical course in the other patients. CONCLUSIONS: Although they occur frequently, postoperative arrhythmias after open-heart procedures in children are associated with low morbidity and mortality.

Small blood volumes from children for quantitative sotalol determination using high-performance liquid chromatography

A sensitive high-performance liquid chromatographic method using fluorescence detection has been developed for sotalol determination in small plasma samples of children and newborns with limited blood volume. In sample sizes of 100 microl of plasma, sotalol was extracted using an internal standard and solid-phase extraction columns. Chromatographic separation was performed on a Spherisorb C6 column of 150x4.6 mm I.D. and 5 microm particle size at ambient temperature. The mobile phase consisted of acetonitrile-15 mM potassium phosphate buffer (pH 3.0) (70:30, v/v). The excitation wavelength was set at 235 nm, emission at 300 nm. The flow-rate was 1 ml/min. Sotalol and the internal standard atenolol showed recoveries of 107+/-8.9 and 97+/-8.1%, respectively. The linearity range for sotalol was between 0.07 and 5.75 microg/ml, the limit of quantitation 0.09 microg/ml. Precision values expressed as percent relative standard deviation of intra-assay varied between 0.6 and 13.6%, that of inter-assay between 2.4 and 14.4%. Accuracy varied between 86.1 and 109.8% (intra-assay) and 95.4 and 103.3% (inter-assay). Other clinically used antiarrhythmic drugs did not interfere. As an application of the assay, sotalol plasma concentrations in a 6-year-old child with supraventricular tachycardia treated with oral sotalol (3.2 mg/kg per day) are reported.

Pharmacologic management of arrhythmias in patients with congenital heart disease

The management of cardiac arrhythmias has evolved rapidly over the past decade. This includes the development of more effective antiarrhythmic medications as well as catheter- and device-based therapies. Antiarrhythmic medications remain the primary treatment modality for most acute arrhythmias; however, the long term use of these medications may be accompanied by severe adverse effects. For this reason, antiarrhythmic medications are increasingly used in conjunction with other forms of therapy, such as catheter ablation or pacemaker implantation. Patients with congenital heart disease often have an increased propensity for cardiac arrhythmias due to both inherent conduction system abnormalities and impaired ventricular function. The purpose of this review is to examine the currently available antiarrhythmic drugs and assess their role in the treatment of arrhythmias in patients with congenital heart disease. It is important to emphasize that patients with congenital heart disease often have hemodynamic limitations and may be at an increased risk for developing adverse effects with antiarrhythmic agents. An awareness of the arrhythmias associated with congenital heart disease, the natural history of these arrhythmias, and the potential benefit of treatment with antiarrhythmic medications versus other forms of therapy provides a rational basis for therapy in this challenging population of patients.

Single-dose pharmacokinetics of sotalol in a pediatric population with supraventricular and/or ventricular tachyarrhythmia

The pharmacokinetics (PK) of the antiarrhythmic sotalol, which elicits Class III and beta-blocking activity, has not been adequately defined in a pediatric population with tachyarrhythmias. The goal of this single-dose study with administration of sotalol HCl at a dose level of 30 mg/m2 body surface area (BSA) was to define the PK of the drug in the following four age groups: neonates (0-30 days), infants (1 month to 2 years), younger children (> 2 to < 7 years), and older children (7-12 years) with tachyarrhythmias of either supraventricular or ventricular origin. The drug was administered in an extemporaneously compounded syrup formulation prepared from the tablets containing sotalol HCl. For safety, vital signs and adverse events were recorded and the QTc interval and heart rate telemetrically monitored. Scheduled blood samples were taken over a 36-hour time interval following dose administration. The drug concentrations in plasma were measured by a sensitive and specific LC/MS/MS assay. Standard compartment model-independent methods were applied to compute the salient PK parameters of sotalol. Twenty-four clinical sites enrolled 34 patients. Thirty-three had analyzable data. Sotalol was rapidly absorbed, with mean peak concentrations occurring 2 to 3 hours after administration. The elimination of sotalol was characterized by an average half-life of between 7.4 and 9.2 hours in the four age groups. There existed statistically significant linear relationships between apparent total clearance (CL/f) or apparent volume of distribution (V lambda z/f) after oral administration and the covariates BSA, creatinine clearance (CLcr), body weight (BW), or age. The best predictors for CL/f were CLcr and BSA, whereas BW best predicted the V lambda z/f. The total area under the drug concentration-time curve in the smallest children with a BSA < 0.33 m2 was significantly greater than that in the larger children. This finding indicated that the BSA-based dose adjustment used in this study led to a larger exposure in the smallest children, whereas the exposure to the drug was similar in the larger children. The dose of 30 mg/m2 was tolerated well. No serious drug-related adverse events were reported. It can be concluded that the PK of sotalol in the pediatric patients depended only on body size, except for the neonates and smallest infants in whom the disposition of sotalol was determined by both body size and maturation of eliminatory processes.

Sotalol in the treatment of fetal dysrhythmias

BACKGROUND

Fetal tachycardia may cause hydrops fetalis and lead to fetal death. No unanimity of opinion exists regarding the optimum treatment. This study evaluates our experience with transplacental sotalol therapy to treat fetal tachycardias in terms of safety and efficacy.

METHODS AND RESULTS

The charts of 21 patients who were treated with sotalol for fetal tachycardia were reviewed. Ten fetuses had atrial flutter (AF), 10 had supraventricular tachycardia (SVT), and 1 had VT. Hydrops fetalis was present in 9 fetuses. Drug treatment was successful in establishing sinus rhythm in 8 of 10 fetuses with AF and in 6 of 10 fetuses with SVT. The mortality rate in this study was 19% (4 of 21 fetuses; 3 had SVT and 1 had AF); 3 deaths occurred just days after the initiation of sotalol therapy, and 1 occurred after a dosage increase. At birth, tachycardia was present in 6 infants. Two patients who converted to sinus rhythm in utero suffered from neurologic pathology postnatally.

CONCLUSIONS

Fetal tachycardia is a serious condition in which treatment should be initiated, especially in the presence of hydrops fetalis. The high success rate in fetuses with AF suggests that sotalol should be considered a drug of first choice to treat fetal AF. The low conversion rate and the fact that 3 of the 4 deaths in this study occurred in fetuses with SVT indicate that the risks of sotalol therapy outweigh the benefits in this group and that sotalol should, therefore, be limited in the treatment of fetal SVT.

Antiarrhythmic drug therapy in the neonate

The neonate presents a challenge for the practitioner considering antiarrhythmic therapy: pharmacokinetics are different than in older children or adults; and the arrhythmia substrate may also differ, with respect to issues of ion channel and autonomic nervous system development. This paper reviews the need for antiarrhythmic drug therapy in the neonate, developmental aspects of pharmacokinetics, autonomic regulation and cellular electrophysiology and the antiarrhythmics available today with an emphasis on newer drug therapy.

Results of a restrictive use of antiarrhythmic drugs in the chronic treatment of atrioventricular reentrant tachycardias in infancy and childhood

Childhood supraventricular tachycardia (SVT) carries a good prognosis. Thus, treatment should be based on the use of drugs with a low risk of such potentially serious side effects as proarrhythmia, which is well documented for class I and III drugs in children. We studied all pediatric patients with a first manifestation of SVT between 1988 and the end of 1995 who were seen for a follow-up examination, including Holter monitoring, during 1996. The minimum follow-up period was 12 months. Fifty children met study entry criteria. Mean patient age at first presentation was 2 years (median 1 month), with 33 of the patients (66%) having experienced their first episode of tachycardia in their first year of life. Of 39 patients initially treated with either digoxin or a beta blocker, SVT in 29 (75%) responded favorably to this treatment. There were no adverse effects. Of the 10 children whose disease did not respond to these first-line agents, 9 (23% of those treated) required class I or III antiarrhythmic drugs. Thus, first-line antiarrhythmic long-term prophylaxis using drugs with a favorable risk profile, such as digoxin and beta blockers, resulted in successful disease management in a large proportion of unselected children, avoiding the need for chronic use of class I or class III antiarrhythmic drugs.

Ventriculo-atrial time interval measured on M mode echocardiography: a determining element in diagnosis, treatment, and prognosis of fetal supraventricular tachycardia

OBJECTIVE

To determine whether M mode echocardiography can differentiate fetal supraventricular tachycardia according to the ventriculo-atrial (VA) time interval, and if the resulting division into short and long VA intervals holds any relation with clinical presentation, management, and fetal outcome.

DESIGN

Retrospective case series.

SUBJECTS

23 fetuses with supraventricular tachycardia.

MAIN OUTCOME MEASURES

A systematic review of the M mode echocardiograms (for VA and atrioventricular (AV) interval measurements), clinical profile, and final outcome.

RESULTS

19 fetuses (82.6%) had supraventricular tachycardia of the short VA type (mean (SD) VA/AV ratio 0.34 (0.16); heart rate 231 (29) beats/min). Tachycardia was sustained in six and intermittent in 13. Hydrops was present in three (15.7%). Digoxin, the first drug given in 14, failed to control tachycardia in five. Three of these then received sotalol and converted to sinus rhythm. All fetuses of this group survived. Postnatally, supraventricular tachycardia recurred in three, two having Wolff-Parkinson-White syndrome. Four fetuses (17.4%) had long VA tachycardia (VA/AV ratio 3.89 (0.82); heart rate 226 (10) beats/min). Initial treatment with digoxin was ineffective in all, but sotalol was effective in two. Heart failure caused fetal death in one and premature delivery in one. All three surviving fetuses had recurrences of supraventricular tachycardia after birth: two had the permanent form of junctional reciprocating tachycardia and one had atrial ectopic tachycardia.

CONCLUSIONS

Careful measurement of ventriculo-atrial intervals on fetal M mode echocardiography can be used to distinguish short from long VA supraventricular tachycardia and may be helpful in optimising management. Digoxin, when indicated, may remain the drug of choice in the short VA type but appears ineffective in the long VA type.

Pharmacologic management of supraventricular tachycardias in children. Part 2: Atrial flutter, atrial fibrillation, and junctional and atrial ectopic tachycardia

OBJECTIVE

To review the literature regarding the use of antiarrhythmic agents in the management of atrial flutter (AF), atrial fibrillation (Afib), junctional ectopic tachycardia (JET), and atrial ectopic tachycardia (AET) in infants and children. To discuss the advantages and disadvantages of specific agents in each type of arrhythmia in an effort to develop treatment guidelines.

DATA SOURCE

A MEDLINE search encompassing the years 1966-1996 was used to identify pertinent literature for discussion. Additional references were found in the articles, which were retrieved via MEDLINE.

STUDY SELECTION

Clinical trials that address the use of antiarrhythmic agents for the treatment of supraventricular tachycardia, AF, Afib, JET, and AET in children were selected. Literature pertaining to dosage, pharmacokinetics, efficacy, and toxicity of antiarrhythmic agents in children were considered for possible inclusion in the review; information judged to be pertinent by the authors was included in the discussion.

DATA EXTRACTION

Although there are numerous reports of antiarrhythmic use in children, there are very few large studies designed that evaluate the use of specific antiarrhythmic agents in the treatment of AF, Afib, JET, or AET. Ideally, controlled clinical trials are used to develop clinical guidelines; however, in this situation, most data and information must be obtained from case series of children treated. Although the results from these types of studies may be useful in developing guidelines for the optimal use of these agents for the treatment of AF, Afib, JET, and AET, controlled trials are required for establishing standard treatment guidelines for all patients.

DATA SYNTHESIS

Despite limited scientific evaluation of conventional agents in the treatment of AF, Afib, JET, or AET in children, they continue to be the standards of care. Most information regarding the use of conventional agents in children has been extrapolated from the adult literature. Little justification for the use of the agents or dosing in children is available. Controlled trials regarding the use of newer antiarrhythmic agents (propafenone, amiodarone, flecainide) are available; however, the variance in dosing schemes, presence of structural heart disease, and patient age may confound the results.

CONCLUSIONS

Because of greater clinical experience, conventional antiarrhythmic agents generally remain as first-line therapy in the management of most supraventricular tachycardias in children. Atrial pacing or cardioversion to reestablish sinus rhythm is indicated for initial episodes of AF in infants, followed by chronic prophylactic therapy in those with significant structural heart disease or in infants in whom AF recurs. Attempts to eliminate AF in children outside the neonatal or infancy period should begin with trials of traditional agents such as digoxin or procainamide, and if unsuccessful, subsequent trials of amiodarone. Digoxin and beta-blockers remain the mainstay of therapy for children with Afib, followed by procainamide for treatment failures. Intravenous amiodarone, the newest addition to our antiarrhythmic armamentarium, is the most promising agent in the treatment of postoperative JET. This arrhythmia has been traditionally managed with corporal cooling and/or digoxin therapy; however, intravenous amiodarone may now be a valuable option. Although relatively unsuccessful in the management of congenital JET and AET, conventional agents are typically used prior to the initiation of long-term therapy with potentially more toxic agents such as amiodarone or propafenone. Additional well-designed, controlled trials are needed to further evaluate the comparative efficacy of agents such as flecainide, sotalol, moricizine, propafenone, and amiodarone in the management of AF, Afib, JET, and AET in children, as well as to evaluate the dosing and toxicity in various age groups.

Pharmacologic management of supraventricular tachycardias in children. Part 1: Wolff-Parkinson-White and atrioventricular nodal reentry

OBJECTIVE

To review the literature regarding the use of antiarrhythmic agents in the management of Wolff-Parkinson-White (WPW) syndrome and atrioventricular nodal reentry tachycardia (AVNRT) in infants and children, and to discuss the advantages and disadvantages of specific agents in each arrhythmia in an effort to develop treatment guidelines.

DATA SOURCES

A MEDLINE search encompassing the years 1966-1996 was used to identify pertinent literature for discussion. Additional references were found in the articles that were retrieved via MEDLINE.

STUDY SELECTION

Clinical trials that address the use of antiarrhythmic agents for the treatment of the supraventricular tachycardias WPW and AVNRT in children were selected. Literature pertaining to dosage, pharmacokinetics, efficacy and toxicity of antiarrhythmic agents in children were considered for possible inclusion in the review, and information judged to be pertinent by the authors was included in the discussion.

DATA EXTRACTION

Although there are numerous reports of antiarrhythmic use in children, very few large studies are designed to evaluate an individual antiarrhythmic agent for a specific arrhythmia. Controlled, comparison trials of antiarrhythmic agents in children are virtually nonexistent. Ideally, controlled clinical trials are used to develop clinical guidelines; however, in this situation, most data and information must be obtained from case series of children treated. Although the results from these type of studies may be useful in developing guidelines for the optimal use of these agents, controlled trials are required for establishing standard treatment guidelines for all patients.

DATA SYNTHESIS

Despite limited scientific evaluation of conventional agents in the treatment of WPW and AVNRT in children, they continue to be used as standard of care. Most information regarding the use of conventional agents in children has been extrapolated from the adult literature. Little justification for the use of agents or dosing in children is available. Controlled trials regarding the use of new antiarrhythmic agents (propafenone, amiodarone, flecainide) are available; however, the variance in dosing schemes, presence of structural heart disease, and patient age make the development of recommendations difficult.

CONCLUSIONS

Because of greater clinical experience with these conventional antiarrhythmic agents, they continue to be first-line therapy in the management of most supraventricular tachycardia (SVT) in children. The management of SVT in children with WPW syndrome should begin with the use of a beta-blocker with the addition of digoxin or procainamide for treatment failures. The use of digoxin monotherapy, although frequently used by many practitioners in infants and children with WPW, cannot be recommended. For failures to conventional agents, flecainide is the preferred agent, while therapy with propafenone, amiodarone, and sotalol remains to be elucidated. The management of AVRNT is similar to that of WPW; however, digoxin is the agent of first choice. Trials of beta-blockers and procainamide should follow for treatment failures with flecainide again being the preferred "newer" antiarrhythmic for use in resistant cases. Additional well-designed, controlled trials are needed to further evaluate the comparative efficacy of antiarrhythmics in the management of WPW and AVNRT in children, as well as to evaluate dosing and toxicity in various age groups.

Effectiveness of sotalol for atrial flutter in children after surgery for congenital heart disease

This study describes the efficacy of oral sotalol in the treatment and prevention of atrial flutter in children after surgery for congenital heart disease. In 11 of 13 children (85%), conversion to sinus rhythm was achieved, and in 8 of 11 within 24 hours.