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Astemizole |
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indicationAstemizole was indicated for use in the relieving allergy symptoms, particularly rhinitis and conjunctivitis. It has been withdrawn from the market however due to concerns of arrhythmias.pharmacologyAstemizole is a second generation H1-receptor antagonist.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.mechanism of actionAstemizole 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.toxicityLD50=2052mg/kg in micebiotransformationAlmost completely metabolized in the liver and primarily excreted in the feces.absorptionRapidly absorbed from the gastrointestinal tract.half life1 daydrug interactionsAmprenavir: Increased risk of cardiotoxicity and arrhythmiasAprepitant: Increased risk of cardiotoxicity and arrhythmias Bepridil: Increased risk of cardiotoxicity and arrhythmias Cimetidine: Increased risk of cardiotoxicity and arrhythmias Cisapride: Increased risk of cardiotoxicity and arrhythmias Clarithromycin: Increased risk of cardiotoxicity and arrhythmias Delavirdine: Increased risk of cardiotoxicity and arrhythmias Efavirenz: Increased risk of cardiotoxicity and arrhythmias Erythromycin: Increased risk of cardiotoxicity and arrhythmias Fluoxetine: Increased risk of cardiotoxicity and arrhythmias Fluvoxamine: Increased risk of cardiotoxicity and arrhythmias Fosamprenavir: Increased risk of cardiotoxicity and arrhythmias Grepafloxacin: Increased risk of cardiotoxicity and arrhythmias Indinavir: Increased risk of cardiotoxicity and arrhythmias Itraconazole: Increased risk of cardiotoxicity and arrhythmias Josamycin: Increased risk of cardiotoxicity and arrhythmias Ketoconazole: Increased risk of cardiotoxicity and arrhythmias Mesoridazine: Increased risk of cardiotoxicity and arrhythmias Mibefradil: Increased risk of cardiotoxicity and arrhythmias Nefazodone: Increased risk of cardiotoxicity and arrhythmias Nelfinavir: Increased risk of cardiotoxicity and arrhythmias Posaconazole: Contraindicated co-administration Quinine: Increased risk of cardiotoxicity and arrhythmias Quinupristin: This combination presents an increased risk of toxicity Ritonavir: Increased risk of cardiotoxicity and arrhythmias Saquinavir: Increased risk of cardiotoxicity and arrhythmias Sparfloxacin: Increased risk of cardiotoxicity and arrhythmias Telithromycin: Increased risk of cardiotoxicity and arrhythmias Thioridazine: Increased risk of cardiotoxicity and arrhythmias Tipranavir: Tipranavir, co-administered with Ritonavir, may increase the plasma concentration of Astemizole. Concomitant therapy is contraindicated. Troleandomycin: Increased risk of cardiotoxicity and arrhythmias Voriconazole: Increased risk of cardiotoxicity and arrhythmias |