Abstract Astemizole is a synthetic piperidinyl-benzimidazole derivative with white to slightly off-white color, which was used to treat allergies, hives (urticaria), and other allergic inflammatory conditions. Astemizole is an extremely hydrophobic compound (c log P = 5.7) with no solubility in water, slight solubility in ethanol, and good solubility in chloroform and methanol. It is known as an H1-histamine receptor antagonist. It possesses a long duration of action permitting once daily administration. It can induce paresthesia, Torsades de Pointes ventricular arrhythmia, and QT-interval prolongation. Adverse effects associated with astemizole are rare, but some side effects associated with astemizole such as stomach upset and allergic reactions were reported in treated patients. In most countries, astemizole has been withdrawn from the market because of potentially rare side effects involving ventricular arrhythmias and prolongation of the QT interval. Astemizole as a non-sedating and second-generation antihistamine with less sleepiness and intellectual disorder compared with other antihistamines is prescribed to relieve seasonal and perennial allergic rhinitis.