D2.529 - Asymptomatıc QT Prolongatıon Developıng After Antıhıstamıne Use

Introduction: Antihistamines are widely used agents in the pediatric population, and it is known that first-generation antihistamines, in particular, can prolong the QT interval and lead to serious arrhythmias such as torsade de pointes. Although the cardiotoxic potential of second and third-generation antihistamines is significantly lower, it is known that various clinical conditions or concomitant drug use can increase the risk of developing QT prolongation. This report presents a case of incidentally detected QT prolongation in an asymptomatic child patient due to antihistamine use. Case: A three-year-five-month-old male patient was evaluated at the pediatric outpatient clinic as part of a routine athlete screening examination. The patient, who was using desloratadine for allergic rhinitis, had an electrocardiogram (ECG) showing a QTc interval of approximately 500 ms, consistent with QT prolongation. The patient did not experience syncope, palpitations, or cardiovascular symptoms. Following discontinuation of antihistamine treatment, the QTc values ​​regressed. Later, due to recurrent allergic rhinitis and otitis, the patient was evaluated at the ENT outpatient clinic and started on combination therapy including levocetirizine, montelukast, and chlorpheniramine maleate. Due to recurrent infections, the patient was referred to the allergy-immunology clinic, where a follow-up ECG revealed QT prolongation again. After discontinuation of the antihistamines, the QTc returned to age-appropriate normal limits, and no arrhythmia developed. Based on these findings, levocetirizine, desloratadine, and chlorpheniramine maleate were considered as possible agents responsible for QT prolongation. Conclusion: This case demonstrates that even second and third-generation antihistamines can prolong the QT interval in some clinical conditions. When incidental QT prolongation is detected in asymptomatic children, a detailed inquiry into the medication history, especially careful evaluation of QT-prolonging drug combinations, is important. The return of the QT interval to normal upon discontinuation of the drug supports the idea that QT prolongation caused by antihistamines is temporary and reversible. Unnecessary or uncontrolled use of antihistamines should be avoided; in cases of long-term use, monitoring with ECG should be considered.