Discontinue treatment if arrhythmia occurs. Prolonged QT interval. Avoid ethanol or w/ composition of alcohol. Avoid concomitant use w/ QT prolonging medications eg, Ca channel blockers (eg, bepridil, verapamil), TCA, cisapride, quinidine. Concomitant use w/ macrolides eg, erythromycin, clarithromycin; imidazole antifungals eg, ketoconazole, itraconazole, fluconazole; HIV PIs or any CYP450 inhibitors eg, cimetidine, metronidazole, zafirlukast, SSRIs. May affect ability to drive & use machines. Hepatic impairment. 1st trimester of pregnancy. Not recommended in lactation. Childn 2-5 yr (in management of chronic idiopathic urticaria). Childn <2 yr. Elderly.