Astemizole Side Effects

Not all side effects for astemizole may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to astemizole: oral tablet

If you experience any of the following serious side effects, stop taking astemizole and call your doctor immediately or seek emergency medical attention:

  • an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives);

  • an irregular heartbeat;

  • fainting; or

  • seizures.

Other, less serious side effects may be more likely to occur. Continue to take astemizole and talk to your doctor if you experience

  • drowsiness or dizziness;

  • headache;

  • nervousness;

  • nausea, diarrhea, or abdominal discomfort;

  • dry mouth; or

  • dry skin or itchiness.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

For Healthcare Professionals

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

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.

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.


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


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

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