Fexofenadine Azithromycin

The effects of azithromycin 250 mg/day on the pharmacokinetics of desloratadine 5 mg/day and fexofenadine 60 mg bd have been studied in a parallel-group, third-party-blind, multiple-dose, randomized, placebo-controlled study (46). There were small increases (under 15%) in the mean plasma concentrations of desloratadine. In contrast, peak fexofenadine concentrations were increased by 69% and the AUC by 67%. There were no changes in the electrocardiogram. 

Gupta S, Banfield C, Kantesaria B, Marino M, Clement R, Affrime M, Batra V. Pharmacokinetic and safety profile of desloratadine and fexofenadine when coadministered with azithromycin a randomized, placebo-controlled, parallel-group study. Clin Ther 2001 23(3) 451-66. 

The effect of co-administration of azithromycin on plasma concentrations of fexofenadine 60 mg bd has been examined in a randomized third-party-blind, placebo-controlled, parallel-group study in 98 healthy volunteers (5). An initial loading dose of azithromycin (500 mg) was given on day 3, followed by 250 mg od for 4 days. Concomitant azithromycin caused increases in the Cmax and AUC of fexofenadine (69 and 67% respectively). However, there were no statistically significant increases in the PR, QT, QTc interval, QRS complex duration, or ventricular rate after administration of fexofenadine with or without azithromycin. 

There is a case of torsade de pointes possibly due to spiramycin with the sedating antihistamine mequitazine. The situation with erythromycin and loratadine is unclear as one study found that the combination caused a very slight increase in QT interval. Both azithromycin and erythromycin raise fexofenadine levels, but this had no effect on the QT interval, or on adverse events. Azelastine, cetirizine, desloratadine, and intranasal levocabastine seem to be free of clinically relevant interactions with macrolides. 

Fexofenadine levels are raised by both azithromycin and erythromycin but because this does not result in adverse cardiac effects concurrent use is considered safe. Azelastine, cetirizine (and therefore probably its isomer levocetirizine) desloratadine and levocabastine seem to be free from clinically significant pharmacokinetic interactions, and have no cardiac effects, and so may therefore provide suitable alternatives if a non-sedating antihistamine is needed in a patient taking macrolides. 

Fexofenadine 60 mg twice daily Azithromycin 500 mg, then 250 mg daily 5 18 healthy subjects 69% 67% No change 4... 

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