Loratadine administered concomitantly with erythromycin: Pharmacokinetic and electrocardiographic evaluations*

✍ Scribed by Brannan, Melvin D.; Reidenberg, Pascale; Radwanski, Elaine; Shneyer, Lucy; Lin, Chin-Chung; Cayen, Mitchell N.; Affrime, Melton B.

• Book ID: 103037323
• Publisher: Nature Publishing Group
• Year: 1995
• Tongue: English
• Weight: 942 KB
• Volume: 58
• Category: Article
• ISSN: 0009-9236
• DOI: 10.1016/0009-9236(95)90243-0

✦ Synopsis

assessment of potential adverse drug interactions resulting from hepatic cytochrome P450 isozyme inhibition can be evaluated by studying the effects of concomitant administration of one drug with another drug that inhibits specific isozymes.

Cytochrome P4503A4 (CYP3A4) is involved in the metabolism of terfenadine, and erythromycin attenuates the metabolic effect of CYP3A4. Honig et a1.3 reported a potentially serious drug interaction after coadministration of terfenadine, a nonsedating H,receptor antagonist, with erythromycin. This drug interaction appears to be related to plasma accumulation of parent (unmetabolized) terfenadine, shown to be a potent blocker of the myocardial potassium channel, which leads to QT prolongation and the risk of 269 270 Bmnnan et al.