Astemizole

Astemizole Should be taken on an empty stomach.

Porphyria.

Prostatic hypertrophy, urinary retention, glaucoma, pyloroduodenal obstruction, epilepsy; children and elderly. Avoid in patients with cardiac disease, significant hepatic disease, known or suspected prolongation of the QT interval, hypokalaemia and other electrolyte imbalances. Not to exceed recommended doses due to risk of arrhythmias.

Increased appetite, wt gain. Rashes, hypersensitivity reactions. CNS depression eg, drowsiness, headache, psychomotor impairments; urinary retention, dry mouth, blurred vision, GI disturbances.
Potentially Fatal: Ventricular arrhythmias, including torsades de pointes.

Imidazole, triazole antifungals, and the macrolide antibacterials inhibit the hepatic metabolism of astemizole. Avoid concomitant admin of other potentially arrhythmogenic drugs. Co-admin with diuretics may cause electrolyte imbalance. Concurrent use with terfenadine is not recommended.

Grapefruit juice may inhibit the metabolism of astemizole.

Description:
Mechanism of Action: Astemizole is a piperidine derivative, non-sedating antihistamine.
Pharmacokinetics:
Absorption: Rapid absorption from GI tract.
Distribution: Unchanged astemizole: Highly bound to plasma proteins
Metabolism: Extensive 1st pass metabolism.
Excretion: Metabolites are slowly excreted in the urine and faeces, and undergo enterohepatic recycling.

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