Histamen

Histamen - General Information

A long-acting, non-sedative antihistaminic used in the treatment of seasonal allergic rhinitis, asthma, allergic conjunctivitis, and chronic idiopathic urticaria. The drug is well tolerated and has no anticholinergic side effects. [PubChem]

Pharmacology of Histamen

Histamen, an H₁-receptor antagonist, is similar in structure to terfenadine and haloperidol, a butyrophenone antipsychotic. It has anticholinergic (atropine-like) and antipruritic effects.

Histamen for patients

Patients taking Astemizole should receive the following information and instructions. Antihistamines are prescribed to reduce allergic symptoms. Patients taking Astemizole should be advised: 1) to adhere to the recommended dose, and 2) that the use of excessive doses may lead to serious cardiovascular events. DO NOT EXCEED THE RECOMMENDED DOSE. Some patients appear to increase the dose of Astemizole in an attempt to accelerate the onset of action. PATIENTS SHOULD BE ADVISED NOT TO DO THIS, and not to use Astemizole as a p r n product for immediate relief of symptoms. Patients should be questioned about use of another prescription or over-the-counter medication, and should be cautioned regarding the potential for life- threatening arrhythmias with concurrent use of ketoconazole, itraconazole, or erythromycin. Patients should be questioned about pregnancy or lactation before starting Astemizole therapy, since the drug should be used in pregnancy or lactation only if the potential benefit justifies the potential risk to fetus or baby. In addition, patients should be instructed to take Astemizole on an empty stomach e.g., at least 2 hours after a meal. No additional food should be taken for at least 1 hour after dosing. Patients should also be instructed to store this medication in a tightly closed container in a cool, dry place, away from heat or direct sunlight, and away from children.

Histamen Interactions

Ketoconazole/Itraconazole, Macrolides, Including Erythromycin

Histamen Contraindications

Concomitant administration of Astemizole with erythromycin is contraindicated because erythromycin is known to impair the cytochrome P450 enzyme system which also influences astemizole metabolism. There have been two reports to date of syncope with Torsades De Pointes, requiring hospitalization, in patients taking combinations of astemizole 10 mg daily with erythromycin. In each case the QT intervals were prolonged beyond 650 milliseconds the time of the event; One patient also received ketoconazole and the other patient also had hypokalemia.

Concomitant administration of astemizole with ketoconazole tablets is contraindicated because available human pharmacokinetic data indicate that oral ketoconazole significantly inhibits the metabolism of astemizole, resulting in elevated plasma levels of astemizole and desmethylastemizole. Data suggest that cardiovascular events are associated with elevation of astemizole and/or astemizole metabolite levels resulting in electrocardiographic QT prolongation.

Concomitant administration with itraconazole is also contraindicated based on the chemical resemblance of itraconazole and ketoconazole. In vitro data suggest that itraconazole has a less pronounced effect on the biotransformation system responsible for the metabolism of astemizole compared to ketoconazole.

Astemizole is contraindicated in patients with known hypersensitivity to astemizole or any of the inactive ingredients.

Additional information about Histamen

Histamen Indication: For the relief of symptoms associated with seasonal allergic rhinitis and chronic idiopathic urticaria.
Mechanism Of Action: Histamen 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. Histamen may also act on H₃-receptors, producing adverse effects.
Drug Interactions: Amprenavir Increased risk of cardiotoxicity and arrhythmias
Aprepitant 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
Nefazodone Increased risk of cardiotoxicity and arrhythmias
Nelfinavir Increased risk of cardiotoxicity and arrhythmias
Posaconazole Contraindicated co-administration
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
Voriconazole Increased risk of cardiotoxicity and arrhythmias
Mibefradil Increased risk of cardiotoxicity and arrhythmias
Quinine Increased risk of cardiotoxicity and arrhythmias
Quinupristin This combination presents an increased risk of toxicity
Troleandomycin Increased risk of cardiotoxicity and arrhythmias
Food Interactions: Take on an empty stomach, food decreases absorption by 60%.
Generic Name: Astemizole
Synonyms: Not Available
Drug Category: Anti-Allergic Agents; Antihistamines
Drug Type: Small Molecule; Approved; Withdrawn

Other Brand Names containing Astemizole: Alermizol; Astemisan; Astemisol; Astemison; Hismanal; Histamen; Histaminos; Histazol; Kelp; Laridal; Metodik; Nono-Nastizol A; Paralergin; Retolen; Waruzol;
Absorption: Rapidly absorbed from the gastrointestinal tract.
Toxicity (Overdose): LD₅₀=2052mg/kg in mice
Protein Binding: 96.7%
Biotransformation: Almost completely metabolized in the liver and primarily excreted in the feces.
Half Life: 1 day
Dosage Forms of Histamen: Tablet Oral
Chemical IUPAC Name: 1-[(4-fluorophenyl)methyl]-N-[1-[2-(4-methoxyphenyl)ethyl]piperidin-4-yl]benzimidazol-2-amine
Chemical Formula: C28H31FN4O
Astemizole on Wikipedia: https://en.wikipedia.org/wiki/Astemizole
Organisms Affected: Humans and other mammals