Zithrolide Drug Interactions

Antacids: In a pharmacokinetic study investigating the effects of simultaneous administration of antacid with azithromycin, no effects on overall bioavailability was seen although peak serum concentrations were reduced by up to 30%. In patients receiving both azithromycin and antacids, the drug should not be taken simultaneously.
Carbamazepine: In a pharmacokinetic interaction study in healthy volunteers, no significant effect was observed on the plasma levels of carbamazepine or its active metabolite in patients receiving concomitant azithromycin.
Cimetidine: A single dose of cimetidine administered 2 hrs before Zithrolide had no effect on the pharmacokinetics of azithromycin.
Cyclosporin: In the absence of conclusive data from pharmacokinetics or clinical studies investigating potential interaction between azithromycin and cyclosporin, caution should be exercised before concurrent administration of these drugs. If co-administration of these drugs is necessary, cyclosporin levels should be monitored and the dose adjusted accordingly.
Digoxin: Some of the macrolide antibiotics have been reported to impair the metabolism of digoxin (in the gut) in some patients. Therefore, in patients receiving concomitant Zithrolide and digoxin, the possibility of raised digoxin levels should be bourne in mind, and digoxin levels monitored.
Ergot Derivatives: Because of the theoretical possibility of ergotism, Zithrolide and ergot derivatives should not be co-administered.
Methylprednisolone: In a pharmacokinetic interaction study in healthy volunteers, Zithrolide had no significant effect on the pharmacokinetics of methylprednisolone.
Terfenadine: Pharmacokinetic studies have reported no evidence of an interaction between azithromycin and terfenadine. There have been rare cases reported where the possibility of such an interaction could not be entirely excluded; however, there was no specific evidence that such an interaction had occured.
Theophylline: There is no evidence of any pharmacokinetic interaction when azithromycin and theophylline are co-administered in healthy volunteers.
Coumarin-Type Oral Anticoagulants: In a pharmacodynamic interaction study, azithromycin did not alter the anticoagulant effect of a single dose warfarin 15 mg administered to healthy volunteers. There have been reports received in the post-marketing period of potentiated anticoagulant subsequent to co-administration of azithromycin and coumarin-type oral anticoagulants. Although a causal relationship has not been established, consideration should be given to the frequency of monitoring prothrombin time when azithromycin is used in patients receiving coumarin-type oral anticoagulants.
Zidovudine: Single 1000 mg doses, and multiple 1200 mg or 600 mg doses of azithromycin did not affect the plasma pharmacokinetics or urinary excretion of zidovudine or its glucuronide metabolite. However, administration of azithromycin increased the concentrations of phosphorylated zidovudine, the clinically active metabolite, in peripheral blood mononuclear cells. The clinical significance of this finding is unclear, but it may be of benefit to patients.
Didanosine: Co-administration of daily doses of azithromycin 1200 mg with didanosine in 6 subjects did not appear to affect the pharmacokinetics of didanosine as compared with placebo.
Rifabutin: Co-administration of azithromycin and rifabutin did not affect the serum concentrations of either drug. Neutropenia was observed in subjects receiving concomitant treatment of azithromycin and rifabutin. Although neutropenia has been associated with the use of rifabutin, a causal relationship to combination with azithromycin has not been established.