Intravenous Amiodarone for Incessant Tachyarrhythmias
in Children
A Randomized, Double-Blind, Antiarrhythmic Drug Trial
J. Philip Saul, MD; William A. Scott, MD; Stephen Brown, MD; Pablo Marantz, MD;
Valeria Acevedo, MD; Susan P. Etheridge, MD; James C. Perry, MD; John K. Triedman, MD;
Susan W. Burriss, BSN, MS; Paul Cargo, RN; Jay Graepel, PhD; Eeva-Kaarina Koskelo, PhD;
Rebecca Wang, MD; for the Intravenous Amiodarone Pediatric Investigators
Downloaded from http://ahajournals.org by on January 11, 2022
Background—Intravenous (IV) amiodarone has proven efficacy in adults. However, its use in children is based on limited
retrospective data.
Methods and Results—A double-blind, randomized, multicenter, dose-response study of the safety and efficacy of IV
amiodarone was conducted in 61 children (30 days to 14.9 years; median, 1.6 years). Children with incessant
tachyarrhythmias (supraventricular arrhythmias [n⫽26], junctional ectopic tachycardia [JET, n⫽31], or ventricular
arrhythmias [n⫽4]) were randomized to 1 of 3 dosing regimens (low, medium, or high: load plus 47-hour
maintenance) with up to 5 open-label rescue doses. The primary efficacy end point was time to success. Of 229
patients screened, 61 were enrolled during 13 months by 27 of 48 centers in 7 countries. Median time to success
was significantly related to dose (28.2, 2.6, and 2.1 hours for the low-, medium-, and high-dose groups,
respectively; P⫽0.028). There was no significant association with dose for any arrhythmia subgroup, including
JET, but the subgroups were too small for an accurate assessment. Adverse events (AEs) were common (87%),
leading to withdrawal of 10 patients. There were 5 deaths in the 30-day follow-up period (2 possibly related to the
study drug). Dose-related AEs included hypotension (36%), vomiting (20%), bradycardia (20%), atrioventricular
block (15%) and nausea (10%).
Conclusions—In children, the overall efficacy of IV amiodarone, as measured by time to success, was dose related but not
significantly for any arrhythmia subgroup. AEs were common and appeared to be dose related. Although efficacious for
critically ill patients, the dose-related risks of IV amiodarone should be taken into account when treating children with
incessant arrhythmias. Prospective, placebo-controlled trials would be helpful in assessing antiarrhythmic drug efficacy
in children, because their results may differ from retrospective series and adult studies. (Circulation. 2005;112:3470-3477.)
Key Words: arrhythmia 䡲 atrioventricular node 䡲 drugs 䡲 heart defects, congenital 䡲 pediatrics
I
ntravenous (IV) amiodarone hydrochloride (HCl) has
proven efficacy for the treatment of a variety of ventricular and supraventricular arrhythmias (VAs and SVAs)
in adults.1–14 The available data in the literature for
children, from a total of ⬇65 patients, suggest that the drug
is reasonably safe and effective for a variety of VAs and
SVAs, including postoperative junctional ectopic
tachycardia (JET).1,7–9 However, all prior studies have
been unblinded and uncontrolled, leaving the possibility of
bias. Furthermore, despite the fact that the commercially
available preparation of IV amiodarone (Cordarone, Wyeth
Pharmaceuticals) is known to cause significant hypotension in animals15 and adult humans,4 most of the studies in
children have reported minimal hypotensive side effects.1,5–9 Consequently, this study was designed to address
the efficacy and safety of amiodarone IV in a clinical trial.
Because the available uncontrolled reports on amiodarone
IV have noted far greater benefit than risk, investigators
believed it was unethical to include a placebo in the trial.
Given this limitation, this study was designed as a doubleblind, dose-response trial without a placebo group. The
primary objective of this study was to compare the efficacy
Received February 5, 2005; revision received August 5, 2005; accepted September 12, 2005.
From the Medical University of South Carolina, Charleston (J.P.S.); University of Texas Southwestern, Dallas (W.A.S.); University of the Free State,
Bloemfontein, South Africa (S.B.); Hospital Italiano, Buenos Aires, Argentina (P.R.); Hospital Roberto del Rio, Santiago, Chili (V.A.); University of
Utah, Salt Lake City (S.P.E.); Yale University, New Haven, Conn (J.C.P.); Harvard University, Cambridge, Mass (J.K.T.); Wyeth Pharmaceuticals,
Philadelphia, Pa (S.W.B., P.C., J.G., R.W.); and Quintiles (E.-K.K.).
The online-only Data Supplement, which contains an Appendix, can be found with this article at http://circ.ahajournals.org/cgi/
content/full/122/22/3470/DC1.
Correspondence to J. Philip Saul, MD, Medical University of South Carolina, 165 Ashley Ave, PO Box 250915, Charleston, SC 29425. E-mail
saulp@musc.edu
© 2005 American Heart Association, Inc.
Circulation is available at http://www.circulationaha.org
DOI: 10.1161/CIRCULATIONAHA.105.534149
3470
Saul et al
Intravenous Amiodarone in Children
3471
be administered beginning at minute 70 of the study, at the discretion
of the investigator.
The low-dose loading regimen of 1 mg/kg was administered as a
single dose of 1 mg/kg given over the first 10 minutes of the load,
followed by 3 placebo infusions, whereas the medium- and highdose loading regimens were divided into 4 equal doses over the first
study hour. Investigators were encouraged to administer rescue
boluses only when clinically necessary and to allow the patient to
remain in the study through the 47-hour maintenance phase, regardless of drug effect, so long as safety was not compromised. Transient
hypotension could be treated as needed clinically and the patient
could still remain in the study so long as the study drug administration followed the protocol.
AE/Safety Monitoring
Figure 1. Overall study design. Study drug administration was
divided into loading and maintenance phases.
and safety of 3 dose regimens of IV amiodarone in patients
30 days to 16 years old with critical arrhythmias.
Methods
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The study was a randomized, multicenter, double-blind, parallelgroup, dose-response, safety, efficacy, and pharmacokinetic (PK)
study of 61 children aged 30 days through 16 years. A total of 48
centers from the United States, South America, and South Africa
(Appendix in the Data Supplement) participated in the study. Human
studies review groups at each participating center approved the
study. Written, informed consent was obtained from the parent or
legal guardian of each subject, and where appropriate, written assent
was obtained from the study participant. The study design, including
the selection of the patient population and dose regimens, was as
outlined in a written request from the US Food and Drug Administration (FDA).
Inclusion and Exclusion Criteria
Patients aged 30 days through 16 years with ECG documentation of
any incessant SVA and/or VA or with JET if the junctional rate was
⬎95th percentile of heart rate for age15 were eligible for the study.
“Incessant” was defined as persistent tachyarrhythmia with no
intervals of sinus rhythm ⱖ30 seconds in the 30 minutes before
administration of blinded drug therapy. Weight limits were 2 to 75
kg inclusive. Exclusion criteria included (1) use of amiodarone in the
prior 3 months, (2) conditions or other drug use known to have
important interactions with amiodarone, (3) imminent death, and (4)
intentional hypothermia to ⬍35°C to treat the arrhythmia ⱕ3 hours
before study drug initiation. Concomitant antiarrhythmic drug administration was allowed, so long as the other agent(s) remained at
a constant delivery rate for the 1-hour periods before and after study
drug initiation and subsequently remained constant or decreased.
Study Drug
Patients were allocated to receive 1 of 3 blinded dose regimens of IV
amiodarone for 48 hours in equally divided groups (Figure 1). The
randomization was stratified by arrhythmia diagnosis (VA, SVA, or
JET). Drug dosages were based on the prior literature,16 with a 1, 5,
and 10 mg/kg load during the first hour plus a 2, 5, and 10 mg · kg⫺1
· d⫺1 maintenance dose during the subsequent 47 hours for low-,
medium-, and high-dose groups, respectively.17 All loading regimens
occurred during the first study hour in 4 infusions given every 15
minutes over 10 minutes. Because of concerns about amiodarone
causing plastic to leach from the IV tubing at low drug administration rates, all maintenance administration was given as a series of
equally divided boluses, each infused every 2 hours over 10 minutes.
Thus, the maximum bolus dose was 0.83 mg/kg, comparable to the
doses used currently when amiodarone is administered by a clinician
at the bedside. Drug concentrations were varied accordingly to
maintain blinding. Up to 5 open-label rescue doses of 1 mg/kg could
All patients who received at least 1 dose of the study drug were
monitored for 30 days for adverse events (AEs) and safety. Safety
blood samples drawn before and periodically during the study
included electrolytes, a complete blood count, and thyroid, renal, and
liver profiles. Heart rate, ECG, and blood pressure changes were
monitored during drug administration for AEs. Hypotension and
bradycardia during loading were also classified according to whether
or not they had potential clinical significance, defined as a systolic
blood pressure fall of ⱖ20 mm Hg, a diastolic blood pressure fall of
ⱖ10 mm Hg, and a heart rate fall to ⱕ50th percentile for age.18,19
PK Evaluation
PK studies were performed at US sites only. Blood samples (0.5 mL)
for assessment of amiodarone HCl and desethylamiodarone (DEA)
levels were to be taken from all patients during the loading phase and
from patients who had not received any open-label amiodarone
(rescue or outside the study protocol) during the maintenance and
washout phases of the study. Loading-phase samples were drawn
before administration of the first study drug bolus and immediately
(1) at completion of the first bolus (10 minutes), (2) before
administration of the final bolus (45 minutes), (3) at completion of
the final bolus (55 minutes), and (4) before initiation of the
maintenance infusion (120 minutes). Maintenance-phase samples
were drawn immediately (1) before dosing at 8 and 24 hours, (2)
before the last maintenance phase, and (3) before initiation of any
open-label amiodarone. Washout-phase samples were drawn (1)
immediately after the last study drug dose and (2) at trough levels at
2 hours (⫾15 minutes), 4 hours (⫾30 minutes), 8 hours (⫾60
minutes), 24 hours (⫾3 hours), 72 hours (⫾10 hours), 7 days (⫾1
day), 15 days (⫾2 days), and 30 days (⫾4 days).
Data Analysis
Efficacy
Analysis for the intention-to-treat (ITT) population, which included
all randomly assigned patients (n⫽61) who had received at least 1
loading dose of the study medication, is presented in this report.
Individual patients were considered to have a protocol success at the
time they either (1) returned to sustained “sinus” rhythm for ⱖ10
minutes or (2) for JET patients, had a reduction in heart rate to ⱕ180
bpm and the heart rate was 20% lower than baseline for ⱖ10 minutes,
both without any 30-second period of arrhythmia.
The study had 2 primary end points. One was the traditional time
to success for the ITT population. It was anticipated that the use of
rescue boluses would confound assessment of the dose response by
reducing the differences in the actual administered dose; thus, a
composite end point combining the time to success with the
time-to-rescue-bolus was also defined as a primary end point.
Secondary end points included that proportion of patients who had
arrhythmia termination, at least 1 rescue bolus, recurrent arrhythmia
after initial success, or arrhythmia recurrence requiring rehospitalization, and the number of rescue boluses.
Pharamacokinetics
Concentrations of amiodarone and DEA were used to characterize
the PK profile for the 3 dose regimens. For all patients with PK data,
3472
Circulation
November 29, 2005
TABLE 1.
Demographic and Baseline Characteristics by Dose Regimen
Dose Regimen
Low
(n⫽19)
Medium
(n⫽20)
High
(n⫽22)
JET
9 (47.4)
10 (50.0)
12 (54.5)
31 (50.8)
SVA
9 (47.4)
9 (45.0)
8 (36.4)
26 (42.6)
VA
1 (5.3)
1 (5.0)
2 (9.1)
4 (6.6)
4.3⫾5.1
3.9⫾4.6
4.1⫾4.8
4.1⫾4.7
1.7
1.5
1.6
1.6
0.2–13.8
0.1–14.9
0.1–13.9
0.1–14.9
18.3⫾17.1
16.7⫾17.5
16.0⫾14.7
16.9⫾16.2
10.8
10.3
9.2
10.2
4.0–62.2
3.1–75.0
3.4–51.9
3.1–75.0
Characteristic Variable
Total (N⫽61)
Arrhythmia, n (%)
Age, y
Mean⫾SD
Median
Minimum⫺maximum
Weight, kg
Mean⫾SD
Median
Minimum⫺maximum
Total dose during blinded phase, mg/kg
Mean⫾SD
6.2⫾2.9
14.2⫾4.3
24.9⫾9.4
15.6⫾10.0
0.50–10.08
5.42–20.08
7.50–34.92
0.50–34.92
US
8 (42.1)
12 (60.0)
12 (54.5)
32 (52.5)
Non-US
11 (57.9)
8 (40.0)
10 (45.5)
29 (47.5)
Minimum⫺maximum
Geographic location, n (%)
Abbreviations are as defined in text.
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the following parameters were estimated: (1) Peak and trough
concentrations (Cmax and Cmin) during the loading phase, (2) average
concentrations (Cm,avg) during the maintenance phase according to the
areas under the concentration-time curves from an 8-hour time point
to the last sampling point t during maintenance administration
(AUC8-t) divided by the interval of 8 hours to t. These parameters
were also assessed for any dose effect. For patients who did not
receive a rescue bolus and were not switched over to open-label
amiodarone at the end of study drug treatment, the terminal disposition PK characteristics were assessed by (1) the rate constant (z)
obtained from a monoexponential regression of the last 4 concentration points and (2) the half-life (t1/2), calculated as t1/2⫽ln2/z.
Amiodarone clearance and its possible association with age were
also assessed.
Statistical Considerations
By assuming a proportional-hazards model with 30% and 80% treatment successes in the low- and high-dose groups, respectively, and 20
patients per group, we found that the study had ⬇80% power to detect
a statistically significant dose-related trend (␣⫽0.05, 2 side; hazard
ratios of ⬇1.9 and 4.5, respectively). For the time to success and other
time-related end points, the distributions of these times were estimated
by Kaplan-Meier methods.5 Dose response was analyzed by a
proportional-hazards model1,6 –10 with loading dose as the independent
variable and arrhythmia type as a stratification variable and an interaction term to assess differential dose effect by arrhythmia subtype. Tests
for trends on categorical variables were done with Cochran-MantelHaenszel tests3 and on continuous variables with a general linear model.
The effect of arrhythmia type (SVA and JET only) on the dose response
for time to success was also assessed with the proportional-hazards
model. A separate evaluation was not done for the VA group because it
contained only 4 patients. Unless specified otherwise, data are reported
as mean⫾SD. For all evaluations, a probability value of ⬍0.05 was
considered statistically significant. All calculations were done with SAS
software (SAS Institute, Inc; SAS/STAT User’s Guide, version 8).
Results
Subjects and Enrollment
A total of 221 patients were screened by 48 participating
centers, resulting in randomization of 61 patients from 27
centers during a period of 13 months, yielding an enrollment
rate of just under 0.1 patients per center per month. Screen
failures occurred for a variety of reasons, including young age
and an unstable medical condition requiring immediate treatment. Just over half of the randomized patients had an
arrhythmia diagnosis of JET, whereas 42% had an SVA and
4 patients had a VA. The study population had a broad range
of ages and weights (Table 1).
Of the 61 patients, 36 completed the 48-hour blinded
phase, and 25 were withdrawn from the blinded phase for the
following reasons: 10 because of AEs, 10 for lack of efficacy
after receiving at least 1 rescue bolus, and 5 at the discretion
of the investigator or sponsor. Of the 41 patients who met the
primary end point, 20 patients did not have a documented,
continuous 10-minute ECG rhythm strip. These patients had
conversions verified through a shorter ECG strip and/or
physician and chart confirmation of the 10-minute rhythm,
which was thought to be diagnostically adequate in every
case, despite not meeting the exact criteria in the original
protocol.
Concurrent Cardiac Disease
The majority of patients (n⫽43, 71%) had concurrent cardiac
disease contributing to their arrhythmias (Table 2). Congenital heart disease, cardiomyopathy, and preexcitation were the
most frequent associated cardiac conditions. Furthermore, in
Saul et al
TABLE 2.
Intravenous Amiodarone in Children
3473
Concurrent Cardiac Disease by Arrhythmia Type
Concurrent Cardiac Disease
Congenital
Heart
Arrhythmia Disease Cardiomyopathy Preexcitation Postsurgical None
Overall
43
7
4
37
12
JET
28
0
0
28
3
SVA
13
4
3
9
9
VA
2
3
1
0
0
Abbreviations are as defined in text. Patients may have had ⬎1 concurrent
cardiac disease.
37 patients (61%), the qualifying arrhythmia occurred in the
immediate postoperative period after congenital heart surgery, including 28 of 31 patients with JET (90%).
Figure 2. Time to success for the overall ITT population. Abbreviations are as defined in text.
Concomitant Medications
All patients were receiving at least 1 concomitant medication,
with most receiving ⬎1, reflecting the severity of the patients’ conditions. The most common concomitant medications were dopamine (49%), furosemide (48%), digoxin
(43%), milrinone (33%), captopril (21%), dobutamine (20%),
and epinephrine (16%).
maintained throughout the remainder of the study; however,
as rescue boluses and maintenance therapy were given,
responses in the low-dose group narrowed the difference
among the groups during the first 30 study hours. A total of
20 patients did not reach this efficacy end point, 13 because
of early withdrawal and 7 who completed the 48-hour study
period without efficacy.
Downloaded from http://ahajournals.org by on January 11, 2022
Treatment Compliance
A total of 3 patients were administered the incorrect dose of
study drug. Two patients received an overdose of study drug
(123% and 106%) based on incorrect body weight measurements, and 1 patient was underdosed by 50% as a result of a
drug administration error.
Composite-Rank End Point
This composite end point was not statistically significant
(P⫽0.231) for the overall group and was thought not to be
clinically relevant to the analysis. Consequently, for brevity,
it is not discussed further in this report.
Efficacy Evaluation
Secondary End Points
Primary End Point
Outcome Status
Outcome status is presented in Table 3. At the completion of
the study, there were fewer successes in the low-dose group
(47%) relative to the medium- (80%) and high- (73%) dose
groups, but there was no statistically significant trend. At the
end of the loading dose, there appeared to be increased
success in the high-dose group (41%) compared with the
medium- and low-dose groups (25% and 16%, respectively;
P⫽0.083), but the difference did not reach statistical significance. In general, the numbers of premature withdrawals
were comparable among the 3 groups (5, 3, and 5 in the low-,
medium-, and high-dose groups, respectively).
Time to Success
The median time to success for the low-, medium-, and
high-dose groups was 28.2, 2.6, and 2.1 hours, respectively,
with a statistically significant dose relation such that a higher
dose was associated with a shorter time to success (hazard
ratio⫽1.103; 95% confidence interval, 1.011 to 1.205;
P⫽0.028; Figure 2). Early responders were seen during and
just after the loading phase in all 3 dose groups, with the
largest frequency of response occurring in the medium- and
high-dose groups, and a very low response rate in the
low-dose group. This early difference among groups was
TABLE 3.
Efficacy and Patient Status by Dose Group
Dose Group
Results
Low
(n⫽19)
Successful at 70 minutes, n (%)
3 (15.8)
Successful at end of study, n (%)
9 (47.4)
Medium
(n⫽20)
5 (25.0)
16 (80)
High
(n⫽22)
P Value
for Trend
9 (40.9)
0.083
16 (72.7)
0.155
Completed 48 hours without success, n
5
1
1
䡠䡠䡠
Premature withdrawal for AE, n
1
0
2
䡠䡠䡠
Withdrawal for lack of efficacy, n
2
3
2
䡠䡠䡠
Withdrawal, investigator discretion, n
2
0
1
䡠䡠䡠
Abbreviations are as defined in text.
3474
Circulation
TABLE 4.
November 29, 2005
Other Secondary End Points by Dose Group
Dose Group
Low
(n⫽19)
Medium
(n⫽20)
Bolus required, n (%)
10 (52.6)
14 (70.0)
11(50)
0.700
No. of boluses*
2.4⫾2.4
2.5⫾2.1
1.6⫾2.1
0.219
Recurrent arrhythmias during blinded
phase, n (%)
5 (26.3)
5 (25)
5 (22.7)
0.655
Blinded phase arrhythmia-free hours
(proportion of 48 hours, %)
26.9⫾36.7
55.9⫾41.0
53.9⫾42.4
0.053
0
0
0
䡠䡠䡠
Results
High
(n⫽22)
P Value
for Trend
Rescue bolus related
Recurrence related
Hospitalization for arrhythmias during 30-d
follow-up, n
*Average includes zero for patients not receiving a bolus.
Rescue Bolus and Recurrence Related End Points
There was no dose-response relation (Table 4) for the
administration of rescue boluses. The percentage of arrhythmia-free hours during the total blinded phase increased with
dose, nearly reaching significance (P⫽0.053). This finding is
consistent with the shorter time to success at higher doses,
because the earlier successes should have yielded a longer
arrhythmia-free period. No patient was rehospitalized for
arrhythmia recurrence during the 30-day follow-up period.
Arrhythmia Subtypes Analysis: JET and SVA
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There was no significant interaction between arrhythmia type
and dose response (Figure 3 and Table 5; P⫽0.862), suggesting that the dose response in both SVA and JET was similar
to the overall group response. However, when the 2 subgroups were analyzed independently, no significant dose
response could be demonstrated for either SVA or JET
(Figure 3). Interestingly, in all dose groups, the JET patients
had a high rate of success during the blinded portion of the
study, ranging from 67% (low dose) to 83% (high dose)
(Table 5). Alternatively, for SVA, the conversion rates were
more scattered, ranging from 33% (low dose) to 89% (medium dose), again with no clear relation to dose for the
conversion rate or time to success (Table 5).
Safety Evaluation
Total exposure to amiodarone during the blinded phase of the
study (study drug plus open-label IV rescue boluses) ranged
from 6 to 25 mg/kg (Table 1). AEs (Table 6 and Table 7)
occurred in 87% of patients, ranging between 80% and 91%
for the 3 dose groups. A wide variety of AEs from multiple
organ systems was reported. The number of AEs in each
group was too small for an accurate statistical analysis;
however, only 5 AEs appeared to be both dose related and
occurred in ⬎1 patient: Hypotension (36.1%), vomiting
(19.7%), bradycardia (19.7%), atrioventricular block
(14.8%), and nausea (9.8%) (Table 6). Most of these events
occurred within 4 hours, when there was the clearest separation of dose and success among the groups.
A total of 24 patients (39.3%) reported at least 1 significant
AE during the study, but only hypotension, bradycardia, and
atrioventricular block appeared to be both dose related and
occurred in ⬎1 patient (Table 6). The rate of clinically
significant changes in heart rate and blood pressure during
loading, as defined in Methods, appeared to be dose related
(Table 7). A total of 10 patients were withdrawn for significant safety issues: 4 for hypotension, 5 for bradycardia, and 3
for atrioventricular block. These withdrawals appeared to be
dose related, occurring in 1, 4, and 5 patients from the low-,
medium-, and high-dose groups, respectively. There were no
dose-related changes in any of the laboratory parameters,
including hepatic (alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase), thyroid (reverse triiodothyroxine, triiodothyroxine, thyroxine, thyroidstimulating hormone), and renal (creatinine, blood urea
Figure 3. Time to success for arrhythmia
subgroups of JET and SVA. No interaction of subgroup and dose was present
(P⫽0.862). Abbreviations are as defined
in text.
Saul et al
TABLE 5.
Intravenous Amiodarone in Children
3475
Outcomes for Arrhythmia Subgroups: SVA and JET
Dose Group
Low
(n⫽19)
Medium
(n⫽20)
High
(n⫽22)
Success at end of load, n (%)
SVA
2/9 (22.2)
2/9 (22.2)
3/8 (37.5)
JET
1/9 (11.1)
2/10 (20.0)
4/12 (33.3)
SVA
3/9 (33.3)
8/9 (89.0)
4/8 (50.0)
JET
6/9 (66.7)
7/10 (70.0)
10/12 (83.3)
Success at end of blinded
phase, n (%)
Abbreviations are as defined in text.
nitrogen) function studies at any time point through 30 days.
Of the 20 patients who underwent peripheral IV study drug
administration, 5 (25%) developed phlebitis.
Deaths
There were 5 deaths during the 30-day follow-up period. All
of the deaths were considered by the investigators to be
unrelated to the study protocol or medication; however, 2 of
the deaths (1 in the medium-dose and 1 in the high-dose
group) occurred within 24 hours of significant, hypotensive
AEs that, in review of the data, could have been related to
study drug and may have contributed to the patients’ subsequent death.
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Pharmacokinetics
The PK evaluation was planned for patients enrolled in the
United States only (n⫽32) or Canada (n⫽0). Of the 32
patients, 3 were excluded for acquisition or technical issues.
Four of the remaining 29 patients completed PK sampling for
the loading-dose, maintenance, and washout phases. The
remaining 25 patients all had loading-phase data, whereas a
few had maintenance data and none had washout data.
There was a dose-related increase in Cmax, Cavg, and the area
under the curve, which, when normalized for dose, demonstrated no significant effect of dose on PK properties (Figure
4). The maximum concentration during loading occurred at
TABLE 6.
AEs by Dose Group
Dose Group
ⱖ1 AE, n (%)
Low
(n⫽19)
Medium
(n⫽20)
High
(n⫽22)
Total
(N⫽61)
17 (89.5)
16 (80.0)
20 (90.9)
53 (86.9)
Hypotension, n (%)
5 (26.3)
7 (35.0)
10 (45.5)
22 (36.1)
Bradycardia, n (%)
0 (0.0)
6 (30.0)
6 (27.3)
12 (19.7)
Atrioventricular block, n (%)
2 (10.5)
3 (15.0)
4 (18.2)
9 (14.8)
Vomiting n (%)
1 (5.3)
3 (15.0)
8 (36.4)
12 (19.7)
Nausea, n (%)
1 (5.3)
1 (5.0)
4 (18.2)
6 (9.8)
24 (39.3)
ⱖ1 significant AE, n (%)
6 (31.6)
8 (40.0)
10 (45.5)
Hypotension, n (%)
0
1 (5.0)
3 (13.6)
4 (6.6)
Bradycardia, n (%)
0
1 (5.0)
2 (9.1)
3 (4.9)
Atrioventricular block, n (%)
1 (5.3)
1 (5.0)
1 (4.5)
3 (4.9)
Abbreviations are as defined in text.
Figure 4. Loading-phase PK. Cmax (upper left), Cavg, and area
under the curve (AUC) for each dose level (upper right). Cavg and
AUC were also normalized for dose (lower right). Other abbreviations are as defined in text.
10⫾0 minutes for the low dose and 50⫾14 minutes for both
the medium and high doses. Although samples were available
for only a few patients who completed the maintenance
phase, it was clear that there was a rapid drop in amiodarone
concentrations (Figure 5) and a slow increase in DEA trough
levels (not shown) soon after the loading-dose and initiation
of the reduced dose for maintenance. In fact, amiodarone
concentrations during the maintenance phase were consistently ⬍1 g/mL for even the high-dose protocol. For the 3
patients with complete washout-phase data, the amiodarone
t1/2 values were 9.3, 6.9, and 11.4 days (Figure 6, right).
Finally, there was a strong trend toward an increase in
dose-normalized Cavg with age (P⫽0.06, Figure 6, left),
suggesting a decrease in clearance of the drug from the
plasma with age.
Discussion
This study is the first randomized, double-blind, therapeutic
trial of an antiarrhythmic drug performed in a pediatric
population. There were a number of important findings. First,
IV amiodarone had a significant dose response for pediatric
patients with a variety of critical arrhythmias, with a shorter
time to success for the 2 higher-dose groups (5 and 10 mg/kg)
than the low-dose group (1 mg/kg). However, possibly
because of small sample size, this study could not demonstrate an independent dose response for the arrhythmia
subtypes of SVA or JET, despite the very strong indications
from uncontrolled studies in the literature that IV amiodarone
is efficacious for the treatment of JET.1,4 –10,20 Finally, though
efficacious, there was a high rate of clinically significant AEs
that appeared to be dose related, including hypotension,
bradycardia, and atrioventricular block. Taken together, the
results strongly support the use of randomized trials (preferably placebo controlled) to assess the efficacy and safety of
pharmacological agents used in pediatric patients with significant heart disease.
On the basis of a variety of randomized, controlled trials,
IV amiodarone has been shown to have a favorable riskbenefit profile,7 leading to its approval by the FDA for adults
with stable but critical arrhythmias, as well as in the setting of
3476
Circulation
November 29, 2005
TABLE 7.
the Load
Potentially Significant Blood Pressure and Heart Rate Changes During
Low Dose
(n⫽19)
Medium Dose
(n⫽20)
High Dose
(n⫽22)
Total
(N⫽61)
SBP decrease ⱖ20 mm Hg, n (%)
2 (10.5)
4 (20.0)
9 (40.9)
15 (24.6)
DBP decrease ⱖ10 mm Hg, n (%)
5 (26.3)
8 (40.0)
12 (54.5)
25 (41.0)
Heart rate ⱕ50th percentile for age, n (%)
2 (10.5)
5 (25.0)
6 (27.3)
13 (21.3)
SBP and DBP indicate systolic and diastolic blood pressure, respectively. Abbreviations are as
defined in text.
Downloaded from http://ahajournals.org by on January 11, 2022
a cardiac arrest.21,22 Although no randomized trials have been
performed in the pediatric population, a number of uncontrolled studies have been performed, suggesting a similar
risk-benefit profile to that in adults. Totaling ⬇65 patients,
these studies have reported overall rates for complete or
“partial” efficacy of ⬇86% and for JET of ⬇95%. Furthermore, in doses similar to the medium- and high-dose groups
in this study, AEs were reported to be uncommon, with
hypotension (defined variably) in only ⬇10% of the patients
across all studies and few other side effects. One of the
studies was performed prospectively and protocol driven, but
no study included comparison therapies, blinded or unblinded. Based largely on these reports, IV amiodarone has
become the treatment of choice for many children with
critical arrhythmias and most cases of postoperative JET.
Furthermore, IV amiodarone has now been added to the
Pediatric Advanced Life Support protocols for conversion of
resistant ventricular arrhythmias, despite the lack of any
studies investigating its role in such a setting. Importantly,
although the prospective, blinded data from this study do
support the use of amiodarone for critical arrhythmias, they
also suggest that prior case series of IV amiodarone use in the
pediatric population have overestimated its safety and
efficacy.
Figure 5. Concentration of amiodarone on a logarithmic scale
during the first 24 hours of the protocol for all 3 dose levels.
Note how concentration falls rapidly regardless of dose.
Effect of Arrhythmia Subtype
The fact that there was no significant interaction between
arrhythmia subtype and the dose response for time to success
suggests that the dose responses for SVA and JET were
similar to those for the group as a whole. However, when the
subgroups were analyzed independently, no statistical dose
response could be demonstrated for either SVA or JET by any
end point, possibly because of small sample size. Evaluation
of the outcomes in Table 5 and the time to success curves in
Figure 3, provides several insights. Most JET patients eventually reached a success end point, regardless of dose.
Importantly, however, for the JET patients, the number of
rescue boluses in the 3 dose groups was not different (2.0, 2.6,
and 1.9 for the low-, medium-, and high-dose groups,
respectively). Together, these data suggest that IV amiodarone has at most a weak dose effect for JET. It is also
possible that a dose effect was overwhelmed by a high rate of
spontaneous resolution or that the doses administered were all
too low. Further studies based on a more extensive analysis of
the JET patients in this study may be helpful to clarify these
findings.
Pharmacokinetics
The PK properties of amiodarone IV were generally similar
to those in adults,21,22 demonstrating no effect of dose on the
PK properties during the loading phase and a rapid fall in
plasma concentrations after the load. However, there were a
few differences from adult studies in the PK properties found
in this study that are internally consistent. There was a trend
toward an increase in Cavg with age (P⫽0.061) that suggests
a decrease in clearance of the drug from plasma with
increasing age. There was also a t1/2 of 6.9 to 11.4 days, which
is not as long as that reported in adults. Neither of these
findings is clear enough to recommend age-based changes in
Figure 6. Dose-normalized Cavg vs age (left) and washout-phase
levels for the subjects who had such data (right). Abbreviations
are as defined in text.
Saul et al
drug administration at this time, but they do provide a basis
for further study.
Limitations and Barriers to Study Performance
This study was as remarkable for its completion as for its
outcome. The barriers to performing the study were substantial. Most important was the very small number of pediatric
patients who met the stringent entrance criteria for study
enrollment, leading to the use of 48 centers to enroll 61
patients. In addition, the pediatric arrhythmia specialists
designing and performing this study thought it unethical to
include a placebo group on the basis of existing uncontrolled
studies. The inclusion criteria required that all patients had
critical arrhythmias. Investigators, study coordinators, and
investigational pharmacists had to be available at all times.
Furthermore, the study drug required 20 to 40 minutes to
prepare, which, coupled with the consent process, represented
a recruitment barrier in these critically ill patients. AEs were
common in these patients, and in fact, 5 died during the study.
Virtually all of the barriers to successful completion of the
study discussed also represent limitations for data interpretation. The most important one is the lack of a placebo group.
Despite these limitations, the results did demonstrate that
relying solely on the results of retrospective studies or
prospective studies in adults for evaluating therapeutic options in children is inherently flawed.
Conclusions
Downloaded from http://ahajournals.org by on January 11, 2022
IV amiodarone was shown to have a dose response for the
treatment of a variety of critical supraventricular and ventricular arrhythmias in a pediatric population. The lowest dose of
amiodarone used in this study (1 mg/kg) was not particularly
effective, suggesting that a higher dose should be used.
Efficacy could not be demonstrated in this small population
for any arrhythmia subgroup independently, including JET,
despite the strong indications in the literature of its efficacy
for JET. Serious AEs were common. Hypotension, bradycardia, and atrioventricular block were all dose related and
clinically significant. The results indicate that IV amiodarone
may be both less effective and less safe than suggested in
prior retrospective studies. Thus, IV amiodarone should be
used with caution when treating children with critical arrhythmias. Finally, given the limitations of interpreting this study,
based in part on the lack of a placebo control group, it can be
concluded that whenever possible, a placebo control should
be used to best evaluate the safety and efficacy of antiarrhythmic agents in the pediatric population.
Acknowledgments
This work was supported by grants to the participating centers from
Wyeth Pharmaceuticals.
Disclosure
Dr Saul was a consultant for Wyeth-Ayerst during the design,
performance, and analysis of the study. Drs Graepel and Wang and
S.W. Burriss and P. Cargo were all employees of Wyeth-Ayerst
Intravenous Amiodarone in Children
3477
during the study. Dr Koskelo was an employee of Quintiles, a
clinical research organization responsible for study performance at
centers outside the United States.
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