Drug information of astemizole


 Astemizole is a long-acting, non-sedating second generation antihistamine used in the treatment of allergy symptoms. It was withdrawn from market by the manufacturer in 1999 due to the potential to cause arrhythmias at high doses, especially when taken with CYP inhibitors or grapefruit juice.

Mechanism of effect

Astemizole competes with histamine for binding at H1-receptor sites in the GI tract, uterus, large blood vessels, and bronchial muscle. This reversible binding of astemizole to H1-receptors suppresses the formation of edema, flare, and pruritus resulting from histaminic activity.

 As the drug does not readily cross the blood-brain barrier and preferentially binds at H1 receptors in the peripehery rather than within the brain, CNS depression is minimal. Astemizole may also act on H3-receptors, producing adverse effects.


Astemizole is a second generation H1-receptor antagonist. It does not significantly cross the blood brain barrier and therefore does not cause drowsiness or CNS depression at normal doses.


Absorption: Rapidly absorbed from the gastrointestinal tract.

Volume of distribution: Not Available

Protein binding: 96.7%

Metabolism: Almost completely metabolized in the liver and primarily excreted in the feces.

Half life: 1 day

Drug indications

Allergy , Allergic Rhinitis


The recommended dosage for adults and children 12 years of age and older is 10 mg (1 tablet) once daily.

Patients should be advised not to increase the dose of Astemizole in an attempt to accelerate the onset of action.


Patients known to have conditions leading to QT prolongation may experience QT prolongation and/or ventricular arrhythmias with astemizole at recommended doses. The effect of astemizole in patients who are receiving agents which alter the QT interval is unknown. However, in a view of astemizole's known potential for QT prolongation, it is advisable to avoid its use in patients who are taking medications which are reported to prolong QT intervals (including probucol, certain antiarrhythmics, certain tricyclic antidepressants, certain phenothiazines, certain calcium channel blockers such as bepridil, and terfenadine), patients with electrolyte abnormalities such as hypokalemia or hypomagnesemia, or those taking diuretics with potential for inducing electrolyte abnormalities.
Rare cases of cardiovascular events have been observed in patients with hepatic dysfunction. Systematic evaluation of the pharmacokinetics of astemizole in patients with hepatic dysfunction has not been performed. Since astemizole is extensively metabolized by the liver, the use of Astemizole in patients with significant hepatic dysfunction should generally be avoided.
Caution should be given to potential anticholinergic (drying) effects in patients with lower airway diseases.
Caution should be used in patients with cirrhosis or other liver diseases.
Astemizole does not appear to be dialyzable. Caution should also be used when treating patients with renal impairment.

Points of recommendation

Astemizole was withdrawn from the U.S. market in 1999.

Do not take astemizole (Hismanal) with any of the following medicines: antifungal drugs such as ketoconazole (Nizoral) and itraconazole (Sporanox); antibiotics such as erythromycin , clarithromycin , and troleandomycin ; the malaria medicine quinine (Quinamm); or the medicine nefazodone (Serzone).

Take astemizole on an empty stomach, 1 hour before or 2 hours after eating food.

Do not take astemizole with grapefruit or grapefruit juice. Grapefruit products may increase amount of astemizole available in your body, which could lead to dangerous side effects.

Before taking astemizole, tell your doctor if you have

  • asthma or another lung disease;
  • low potassium levels in your blood;
  • urinary retention or an enlarged prostate;
  • kidney disease;
  • liver disease; or
  • heart disease, especially an irregular heartbeat.

You may not be able to take astemizole, or you may require a dosage adjustment or special monitoring during treatment if you have any of the conditions listed above.

Astemizole is in the FDA pregnancy category C. This means that it is not known whether astemizole will harm an unborn baby. Do not take this medication without first talking to your doctor if you are pregnant.

It is also not known whether astemizole passes into breast milk. Do not take astemizole without first talking to your doctor if you are breast-feeding a baby.

Take the missed dose as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and take only your next regularly scheduled dose. Do not take a double dose of this medication.

Pregnancy level


Related drugs

Cetirizine , Fexofenadine , Loratadin

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