Journal of Pediatric Cardiology and Cardiac Surgery 3(1): 61‒62 (2019)

Images in Pediatric and Congenital Heart Disease

Transient QT Interval Prolongation afterLong-Acting Methylphenidate Overdose
Takumi Sato, MD, PhD and Akira Sato, MD
Department of Pediatrics, National Hirosaki Hospital, Aomori, Japan

Keywords: QT interval prolongation, overdose, methylphenidate
A 12-year-old boy presented at our hospital with agitation, hyperactivity, and excessive talking approximately
3 h after ingesting 216 mg (5 mg/kg) of long-acting methylphenidate (MPH; Concerta®, Janssen PharmaceuticalK.K., Chiyoda, Tokyo, Japan) in a suicide attempt following an altercation with his mother. One month prior
to presentation, he was diagnosed with attention deficit
hyperactivity disorder (ADHD) at another clinic andprescribed 36 mg (0.83 mg/kg) of MPH once daily.
Upon arrival at the hospital, his consciousness level on

the Glasgow Coma Scale was 15, and his vital signs wereas follows: blood pressure, 151/82 mmHg; pulse rate, 100
beats/min; respiration rate, 22 breaths/min; and bodytemperature, 36.7°C. Laboratory tests could not be conducted because the patient was extremely agitated andrefused peripheral venous puncture. A 12-lead electrocardiogram (ECG) revealed prolonged QT interval withcorrected QT intervals of 0.50 s [using the Bazett formula (QTc-B)] and 0.45 s [using the Fridericia formula(QTc-F)] (Fig. 1A). In addition, sinus tachycardia of 100

Fig. 1 Electrocardiogram(A) QTc-B 0.50 s and QTc-F 0.45 s upon admission. (B) both QTc-B and QTc-F 0.42 s on discharge. Fluctuations and myogenic
signals of the baseline are noticeable in (A) because of agitation

Received: March 30, 2018; Accepted: November 12, 2018
Corresponding author: Takumi Sato, MD, PhD, Department of Pediatrics, Hirosaki National Hospital, 1 Tominochou, Hirosaki-shi,Aomori 036‒8545, Japan
E-mail: stakumi@hirosaki-hosp.jp
doi: 10.24509/jpccs.190111© 2019 Japanese Society of Pediatric Cardiology and Cardiac Surgery

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beats/min and mild left axis deviation in the limb leads
were noted. A school-based ECG screening program
did not indicate any abnormality, and the patient had nopersonal or family history of paroxysmal palpitations orsyncope.
He was admitted to our hospital for observation andcardiac monitoring. The following day, he was discharged without any adverse event upon the disappearance of his symptoms. At discharge, both QTc-B and
QTc-F were 0.42 s (Fig. 1B).
Long-acting MPH is among the most commonlyprescribed medications for the treatment of ADHD
and is usually initiated at a daily dose of 18 mg. MPH
inhibits the reuptake of norepinephrine and dopamine
into presynaptic neurons and increases their release into
the extraneuronal space; these events are followed bycentral nervous system stimulation with the simultaneous alteration of sympathetic nervous activity. Several
studies have reported that although sympathomimetic
activity may increase both pulse rate and blood pressure, therapeutic doses of MPH are not associated withan increased risk of serious cardiovascular events. The
product document of Concerta® indicates that meantime to maximum plasma concentration following oral
administration of it occurred between 6 and 10h, followed by elimination half-life with about 3.5 h in thehealthy adults. Although it may be diﬃcult to apply
directly the pharmacokinetics of the therapeutic dose tothat of intoxication dose, careful observation for 12‒24
at least is necessary and valid in cases of an ingested dosecomparable to that in our case.1)
Although increases in pulse rate and blood pressurein the present patient were primarily attributable to an
overdose of MPH, the precise mechanism of QT interval prolongation remains unclear. Magnano et al. havereported that both epinephrine and isoproterenol can
provoke not only tachycardia but also prolonged QTJ Pediatr Cardiol Card Surg Vol. 3, No. 1 (2019)

intervals and U-wave amplitude in healthy subjects2) andthat the fusion of amplified U and T waves might contribute to apparent QT interval prolongation, although
the mechanism of such catecholamine-induced U-wave
amplifications remains unclear. In fact, ECG of the present patient at admission exhibited aberrant and broad Twaves, suggesting the fusion of the U wave with the T
wave following QT interval prolongation.
Recently, the American Heart Association recommended careful evaluation and monitoring of patientswith sudden cardiac death-related heart diseases including hypertrophic cardiomyopathy, long QT syndrome,
Wolﬀ‒Parkinson‒White syndrome, and Marfan syndrome, both before and after the initiation of treatment
for ADHD.3) ECG is the most convenient and important
tool for the evaluation of a patientʼs cardiovascular condition. Considering the transient nature of ECG changes
in our patient, cases of MPH overdose should be closely
monitored on ECG even in the absence of serious cardiac disorders.
Conﬂicts of Interest
The authors have no conflicts of interest to declare.

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disorder: A scientific statement from the America Heartassociation council on cardiovascular disease in the young
congenital cardiac defects committee and the council on
cardiovascular nursing. Circulation 2008; 117: 2407‒2423