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Astemizole Side Effects

Applies to astemizole: oral tablet.


Astemizole and its predominant metabolite, desmethylastemizole, have been associated with prolongation of the QT interval. Most cardiovascular events related to astemizole occur in patients with higher than normal astemizole serum concentrations (either due to ingesting more than the recommended dose of 10 mg once daily or due to reduced elimination) or in patients at risk for cardiac events. Macrolide antibiotic and azole antifungal agents may inhibit the metabolism of astemizole, resulting in QT interval prolongation. Patients with liver dysfunction are also at risk due to decreased metabolism of the drug. Other predisposing factors include congenital forms of QT interval prolongation, coronary artery disease, and electrolyte disorders including hypokalemia and hypomagnesemia. Although rare, arrhythmias have been reported in patients on recommended doses without apparent risk factors[Ref]

Cardiovascular system adverse effects have been associated with the use of astemizole. Adverse effects reported include dizziness, syncopal episodes, palpitations, ventricular arrhythmias (including torsades de pointes), cardiac arrest, and cardiac death.[Ref]

Nervous system

Nervous system adverse effects associated with astemizole are rare. Headaches may occur in approximately 7% of treated patients. Astemizole has not been shown to cause significant drowsiness, sedation, or impair psychomotor skills. Increased appetite and weight gain has been reported in approximately 4% of patients.[Ref]


Gastrointestinal effects of astemizole are rare and include nausea and dry mouth.[Ref]


Rare cases of anaphylaxis, including anaphylactic shock, have been reported.[Ref]

More about astemizole

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Further information

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Some side effects may not be reported. You may report them to the FDA.