AZITHROMYCIN AND TERFENADINE - LACK OF DRUG-INTERACTION

A double-blind placebo-controlled study was conducted in healthy men t o determine the effect of coadministration of azithromycin on the phar macodynamics and pharmacokinetics of terfenadine. Administration of 50 0 mg azithromycin for 1 day and 250 mg on 4 subsequent days did not af fect the pharmacokinetics of the pharmacologically active terfenadine carboxylate metabolite when 60 mg terfenadine was given twice daily fo r 12 days, starting 7 days before azithromycin administration. Terfena dine alone resulted in a 0.010 msec increase in the rate-corrected QT interval (QT(c)), but the incremental effects of azithromycin and plac ebo on QT(c) in volunteers receiving terfenadine were not statisticall y different. It is concluded that the potentially life-threatening dis orders that have been attributed to a pharmacokinetic interaction betw een macrolide antibiotics and terfenadine are unlikely to take place i n patients treated simultaneously with azithromycin and terfenadine.