Astemizole

Astemizole is an antihistamine. Astemizole is an oral H-1 receptor antagonist that is similar in structure to terfenadine, another H-1 receptor antagonist. It provides relief from symptoms of allergies such as rash, hives, watery eyes, runny nose, itching of eyes and sneezing.

Brands
Adult Dose
Dose: 0.143 to 0.428 mg/kg
Single Dose: 0.29 (0.2855)
Frequency: 24 hourly
Route: PO
Instructions: -
Neonatal
Dose:
Single Dose:
Frequency:
Route:
Instructions: Not recommended in this age group
Paedriatic
Dose:
Single Dose:
Frequency:
Route:
Instructions: Not recommended in this age group
Characteristics
. It is of Synthetic origin and belongs to Benzimidazole. It belongs to H1-antagonist pharmacological group on the basis of mechanism of action. The Molecular Weight of Astemizole is 459.00. Its pKa is 8.35.
Contraindications
Astemizole is contraindicated in conditions like Cardiac insufficiency,Hepatic dysfunction.
Effects
Astemizole produces potentially life-threatening effects which include Ventricular fibrillation, Stevens Johnson syndrome. which are responsible for the discontinuation of Astemizole therapy.The signs and symptoms that are produced after the acute overdosage of Astemizole include Cardiac dysrhythmias.The symptomatic adverse reactions produced by Astemizole are more or less tolerable and if they become severe, they can be treated symptomatically, these include Dizziness, Headache, Drowsiness, Nausea, Anxiety, Dry mouth, Pain, Xerostomia.
Indications
Astemizole is primarily indicated in conditions like Allergic conjunctivitis, Allergic rhinitis, Asthma, Dermatitis, Urticaria.
Interactions
Astemizole is known to interact with other drugs, the details of drug interactions is as follows:DrugDetailsSeverityOnsetManagementAmitriptyline (HCl)ArtemisininAzithromycinConcomitant use of both drugs may cause QT-interval prolongation; increased risk of cardiac arrhythmias including ventricular tachycardia and Torsade de pointes. The risk of individual agent or combination of these agents causing ventricular arhythmia in association with QT-prolongation is largely unpredictable but may be increased by some underlying risk factors such as congenital long QT syndrome, cardiac disease and electrolyte disturbances (hypokalemia, hypomagnesemia). In addtion, the extent of drug-induced QT-prolongation is dependent on the perticular drug(s) involved and dosage(s) of the drug(s).ModerateCaution and clinical monitoring recommendedBendrofluazideCetirizineChlorothiazideChlorpheniramine (Maleate)Concomitant use of chlorpheniramine maleate and astemizole increase the risk of arrythmias.MajorContraindicatedChlorthalidoneCisaprideClarithromycinClarithromycin enhances the plasma concentration of astemizole by inhibiting CYP450 3A4 result inincreased plasma level may lead to prolongation of QT interval on the ECG, ventricular arrythmia, cardiac arrest and sudden death.MajorCoadministration is considered contraindicated. Loratadine, cetirizine, or fexofenadine are safer alternatives. Azithromycin and dirithromycin are appropriate alternatives of clarithromycin.DimenhydrinateDothiepin (HCl)ErythromycinErythromycinErytromycin potentiates effect of Astimizole by inhibiting its metabolismFluconazoleFluconazole is a weak inhibitor of CYP450 3A4 enaymatic pathway and may not impair the clearence of astemizole at usual doses.ModerateLoratadine, cetirizine and fexofenadine is considered safer alternatives of astemizole.Fluvoxamine (Maleate)Fluvoxamine inhibits the metabolism of astemizole results in increased concentration may lead to severe cardiotoxicity.MajorIf fluvoxamine given in high doses so caution is recommended.Halofantrine (HCl)Halofantrine (HCl)Halofantrine cause prolongation of QT interval. This condition may be exacerbated when astemizole is given concomitantly may lead to increased risk of ventricular arrhythmia.MajorCoadminitration is considered contraindicated.Perform an ECG before starting therapy with halofantrine and closely monitor cardiac rhythm during and for 8-12 hours after completion of therapy.HydrochlorothiazideIprindoleTheoretical potential for IPRINDOLE increasing the ARRHYTHMOGENIC effect of ASTEMIZOLE. MajorItraconazoleItraconazoleKetoconazoleKetoconazole increases the plasma concentration of astemizole by inhbiting itsmetabolic clearence. Increased plasma level may lead to prolongation of QT interval on ECG, ventricular arrythmia, cardiac arrest and sudden death.MajorCoadministration is considered contraindicated. Loratadine, cetirizine or fexofenadine are considered safer alternatives.Lofepramine (HCl)Theoretical potential for LOFEPRAMINE increasing the ARRHYTHMOGENIC effect of ASTEMIZOLE. Mibefradil (Di HCl)Miconazole (Nitrate)Nefazodone (HCl)Nefazodone increases the plasma concentration of astemizoleresults in increased level which may lead to prolonged QT interval, serious arrythmia and death.MajorThis combinition is considered contraindicated.NelfinavirNevirapinePolythiazideProtriptyline (HCl)QuinineAbout 430 mg quinine increases the plasma concentration of astemizole results in prolongation of QT interval and fatal ventricular arrhythmia.MajorCoadministration is considered contraindicated.RitonavirRitonavir increases the plasma concentration of astemizole by inhibiting its metabolism. Increased plasma level may lead to prolongation of QT interval, ventricular arrythmia, cardiac arrest and sudden death.MajorCoadministration of these agents is considered contraindicated. Loratidine, fexofenadine and cetirizine are considered more safer alternatives.RoxithromycinSotalol (HCl)SpiramycinTerfenadineBoth drugs produce additive effect on cardiac conduction. Coadministration may prolong QT interval and may increase the risk of ventricular arrythmia.ModerateClinical monitoring is advised during concomitant administration. Patient should notify to physician if experience symptoms of torsade de pointes.VORICONAZOLEIncreased risk of cardiotoxicity and arrhythmiasuse with caution These interactions are sometimes beneficial and sometimes may pose threats to life. Always consult your physician for the change of dose regimen or an alternative drug of choice that may strictly be required.
Interfrence
Risks
Drug should not be given to Paediatrics, Pregnant Mothers, and Neonates.If prescribing authority justifies the benefits of the drug against the possible damages he/she should reevaluate them and consult the reference material and previous studies.
Storage
Tab Store in a well closed container, Below 40°C. Protect from Sunlight and Moisture.
Warnings
Astemizole should be used with caution in patients with pre-existing heart, kidney or liver disease, asthma or breathing problems, allergy or a history of drug dependance. It is classified as pregnancy category C. This drug should be used only if clearly needed during pregnancy or lactation.
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