Astemizole drug interactions

Astemizole Hismanal Antihistamine Drug-drug interaction 1988 U.S. 1999 11... 

CYP3A4 is involved in the metabolism of 80%-90% of all currently available drugs (Table 2). Its presence accounts for the majority of the cytochrome enzymes in the liver. It has attracted attention from both physicians and pharmaceutical companies, as there have been incidences of fatal drug interactions, which have resulted in the withdrawal of these drugs from the market (terfena-dine in 1997, astemizole in 1999, and cisapride in 2000). Combinations ofpotent CYP3A4 inhibitors and substrates can drive drug levels to the toxic range. The... 

Concomitant administration of clarithromycin with cisapride, pimozide, astemizole, or terfenadine is contraindicated. There have been postmarketing reports of drug interactions when clarithromycin and/ or erythromycin are coadministered with cisapride, pimozide, astemizole, or terfenadine resulting in cardiac arrhythmias (QT prolongation, ventricular tachycardia, ventricular fibrillation, and torsades de pointes). 

Drug Interactions Increased prothrombin time after warfarin administration Phenytoin Cyclosporine Tolbutamide Tacrolimus Glyburide Glipizide Rifampin Cisapride Terfenadine Astemizole Theophylline ... 

Drug Interactions May enhance anticoagulant effects of coumarin-like drugs Rifampin INH Cyclosporine Phenytoin Hypoglycemic agents Terfenadine Astemizole... 

SSRI drug interactions The SSRls are inhibitors of hepatic cytochrome P450 isozymes, an action that has led to increased activity of other drugs including tricyclic antidepressants and warfarin. Huvoxamine inhibits the metabolism of cisapride, astemizole, and terfena-dine, and the resultant cardiotoxicity has led to the withdrawal of the latter two thugs (see Table 30-3). Citalopram causes fewer drug interactions than other SSRls. 

Cardiotoxicity occurred when ketoconazole was used by patients taking astemizole or terfena-dine, a drug interaction that led to the withdrawal of the two nonsedating antihistamines in the United States. The same type of drug interaction has been reported between ketoconazole and cisapride as a result of the ability of ketoconazole to inhibit hepatic drug-metaholizing enzymes. The answer is (D). 

Besides, the eompetitive substrates for CYP3A4 do not signifieantly give rise to drug-drug interaction, as could be seen with astemizole and terfenadine, by virtue of the fact that the parent molecule (loratadine) overwhelmingly lacks effect on rectifying channels located in the cardiac tissue. 

Important drug interactions occur with the non-sedating antihistamines astemizole and terfenadine. Raised serum levels of these two antihista-... 

Drugs that may interact with miconazole include amphotericin B, astemizole, cisapride, oral anticoagulants, phenytoin, and terfenadine. 

Interactions Erythromycin and clarithromycin inhibit the hepatic metabolism of theophylline, warfarin, terfenadine, astemizole, carbamazepine and cyclosporine which can lead to toxic accumulations of these drugs. An interaction with digoxin may occur in some patients. In this case, the antibiotic eliminates a species of intestinal flora that ordinarily inactivates digoxin, thus leading to greater reabsorption of digoxin from the enterohepatic circulation. 

Rombaut N, Heykants J, Vanden Bussche G. Potential of interaction between the Hrantagonist astemizole and other drugs. Ann Allergy 1986 57(5) 321-4. 

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