Zafirlukast Erythromycin

Administration of zafirlukast and aspirin increases plasma levels of zafirlukast, When zafirlukast is administered with warfarin, there is an increased effect of the anti coagulant. Administration of zafirlukast and theophylline or erythromycin may result in a decreased level of zafirlukast. Administration of montelukast with other drugs has not revealed any adverse responses. Administration of montelukast with aspirin and NSAIDs is avoided in patients with known aspirin sensitivity. Administration of zileuton with propranolol increases the activity or the propranolol with theophylline increases serum theophylline levels and with warfarin may increase prothrombin time (PT). A prothrombin blood test should be done regularly in the event dosages of warfarin need to be decreased. 

Chloral hydrate Chloramphenicol Cimetidine Ciprofloxacin Clofibrate Danazol Disulfiram Doxycycline Erythromycin Fenofibrate Fluconazole Fluorouracil Fluoxetine Fluvoxamine Gemfibrozil Influenza vaccine Isoniazid Itraconazole Fovastatin Metronidazole Miconazole Moxalactam Neomycin Norfloxacin Ofloxacin Omeprazole Phenylbutazone Piroxicam Propafenone Propoyxphene Quinidine Sertraline Sulfamethoxazole Sulfinpyrazone Tamoxifen Testosterone Vitamin E Zafirlukast... 

Drugs that may affect zafirlukast include aspirin, erythromycin, and theophylline. Drugs that may be affected by zafirlukast include warfarin. 

Zafirlukast and montelukast are well tolerated. Zafirlukast increases plasma concentrations of warfarin and decreases the concentrations of theophylline and erythromycin. In rare cases, treatment of patients with CysLT receptor antagonists is associated with the development of Churg-Strauss syndrome, a condition marked by acute vasculitis, eosinophilia, and a worsening of pulmonary symptoms. Because these symptoms often appear when patients are given the leukotriene receptor antagonists when they are being weaned from oral corticosteroid therapy, it is not clear whether they are related to the action of the antagonists or are due to a sudden reduction in corticosteroid therapy. 

Drugs that may inhibit cytochrome P450 metabolism of other drugs include amiodarone, androgens, atazanavir, chloramphenicol, cimetidine, ciprofloxacin, clarithromycin, cyclosporine, delavirdine, diltiazem, diphenhydramine, disulfiram, enoxacin, erythromycin, fluconazole, fluoxetine, fluvoxamine, furanocoumarins (substances in grapefruit juice), indinavir, isoniazid, itraconazole, ketoconazole, metronidazole, mexile-tine, miconazole, nefazodone, omeprazole, paroxetine, propoxyphene, quinidine, ritonavir, sulfamethizole, verapamil, voriconazole, zafirlukast, and zileuton. 

Zafirlukast plasma levels are decreased by erythromycin, but this does not appear to be clinically important No interaction has been found between zafirlukast and azithromycin or clarithromy-... 

A study in 11 asthmatic patients found that erythromycin 500 mg three times daily for 5 days reduced the mean plasma level of zafirlukast 40 mg by about 40%. This reduction in levels would be expected to reduce its antiasthmatic effects. If these drugs are given concurrently, be alert for a reduced response. However, note that the manufacturers do not suggest any alteration in the zafirlukast dosage. ... 

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