| Indication | Astemizole 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 It has been withdrawn from the market however due to concerns of arrhythmias. |
| Pharmacodynamics | 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. |
| Mechanism of action | 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. |
| 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. |
| Route of elimination | Not Available |
| Half life | 1 day |
| Clearance | Not Available |
| Toxicity | LD50=2052mg/kg in mice |
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