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 It was withdrawn from market by the manufacturer in 1999 due to the potential to cause arrhythmias at high doses, especially when taken with CYP inhibitors or grapefruit juice.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
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.
Drug contraindicationsHypersensitivity to this drug or components
Side effectsDiarrhea , Headache , nausea , dry mouth , dizziness , Weight increase , increased appetite , difficulty urinating , tiredness , Abdominal pain , Syncope , conjunctivitis
InteractionsErythromycin , Itraconazole , Ketoconazole , Ziprasidone , Nefazodone , nelfinavir , Zileuton , Dolasetron , vandetanib , Droperidol , sparfloxacin , Procainamide , Dofetilide , Efavirenz , Halofantrine , Grepafloxacin , Mibefradil , Delavirdine , Lercanidipine , Lopinavir and Ritonavir , Roxithromycin , oleandomycin , bedaquiline , Vernakalant , tucatinib , Remoxipride , Fidaxomicin
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Astemizole was withdrawn from the U.S. market in 1999.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.