Astemizole
Astemizole (marketed under the brand name Hismanal, developmental code R43512) was a second-generation antihistamine drug that has a long duration of action. Astemizole was discovered by Janssen Pharmaceutica in 1977. It has been withdrawn from the market in most countries because of rare but potentially fatal side effects (QTc interval prolongation and related arrhythmias due to hERG channel blockade).
QT interval
Prolongation of the QT interval may be due to an adverse drug reaction. Many drugs, such as haloperidol, vemurafenib, ziprasidone, methadone and sertindole, can prolong the QT interval. Some antiarrhythmic drugs, like amiodarone or sotalol, work by getting a pharmacological QT prolongation. Also, some second-generation antihistamines, such as astemizole, have this effect. In addition, high blood alcohol concentrations prolong the QT interval. A possible interaction between selective serotonin reuptake inhibitors and thiazide diuretics is associated with QT prolongation. Macrolide and fluoroquinolone antibiotics are also suspected to prolong the QT interval. It was discovered recently that azithromycin is associated with an increase in cardiovascular death.