Cetirizine a safe antihistamine in long QT syndrome.SAN FRANCISCO -- Cetirizine appears to be the antihistamine antihistamine (ăn'tĭhĭs`təmēn), any one of a group of compounds having various chemical structures and characterized by the ability to antagonize the effects of histamine. of choice for patients with long QT syndrome because of the drug's lack of effect on ventricular repolarization repolarization /re·po·lar·iza·tion/ (re-po?ler-i-za´shun) the reestablishment of polarity, especially the return of cell membrane potential to resting potential after depolarization. , Dr. Anna-Mari Hekkala said at the annual meeting of the Heart Rhythm Society.
Prolongation of the QT interval has been a problem with some other antihistamines. Two nonsedating ones--terfenadine and astemizole--have been removed from the U.S. market for this reason. Any prolongation of the QT interval would be of particular concern in patients with long QT syndrome because it would exacerbate their increased risk of sudden cardiac death Sudden Cardiac Death Definition
Sudden cardiac death (SCD) is an unexpected death due to heart problems, which occurs within one hour from the start of any cardiac-related symptoms. SCD is sometimes called cardiac arrest. , said Dr. Hekkala of the University of Helsinki (Finland).
She reported on 30 asymptomatic patients with one of the two most common forms of congenital long QT syndrome. Half had the HERG mutation; the rest had the KCNQ1 mutation. They took 10 mg/day of cetirizine for 4 days and 10 mg of placebo daily for another 4 days, as did 15 healthy control subjects. After each dosing, their ECGs were studied at rest and during maximal exercise stress testing.
Cetirizine had no significant effect on QT interval at rest, during exercise, or during recovery. Nor did 10 mg of cetirizine affect resting or maximal heart rate, blood pressure, or achieved workload. In fact, in patients with either form of long QT syndrome, cetirizine was tied to significant shortening of the T-wave end, resulting in a salutary mild reduction in transmural transmural /trans·mu·ral/ (trans-mu´ral) through the wall of an organ; extending through or affecting the entire thickness of the wall of an organ or cavity.
adj. dispersion of repolarization.