Zafirlukast Clarithromycin

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. 

Although zafirlukast inhibits CYP3A, it did not have any significant pharmacokinetic effect on single doses of azithromycin or clarithromycin in 12 healthy volunteers (190). 

Garey KW, Peloquin CA, Godo PG, Nafziger AN, Amsden GW. Lack of effect of zafirlukast on the pharmacokinetics of azithromycin, clarithromycin, and I4-hydroxyclarithromycin in healthy volunteers. Antimicrob Agents Chemother I999 43(5) 1152-5. 

Zafirlukast 20 mg bd for 12 days did not interfere with the metabohsm of azithromycin or clarithromycin (8). However,... 

Zafirlukast is an inhibitor of the cytochrome P450 isoenzyme CYP3A4 in vitro. However, a study in 12 healthy subjects found that zafirlukast 20 mg twice daily for 12 days did not significantly affect the pharmacokinetics of a single 500-mg dose of azithromycin or clarithromycin. No precaution would seem necessary if zafirlukast is given with azithromycin or clarithromycin. 

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