Telithromycin

Elsewhere in this issue, Clay and colleagues (1) describe a serious adverse event related to telithromycin. This report should cause physicians who prescribe telithromycin to pause in order to be sure it is the right antibiotic for the circumstances. Herein we provide information about telithromycin to help clinicians decide when to prescribe it.

Telithromycin (Ketek, Aventis Pharmaceuticals, Bridgewater, New Jersey), the first marketed ketolide antibiotic, is a modification of the macrolide structure. Like macrolides (2), telithromycin blocks protein synthesis (3). However, compared with macrolides, it has increased affinity for the binding sites on domains II and V of the 50S ribosomal subunit (4). This attribute provides increased activity against bacteria that are resistant to macrolides because of both methylation- and efflux pump–mediated mechanisms (ermB and mefA, respectively) (2). Telithromycin is active in vitro against bacterial pathogens most commonly isolated from patients with mild to moderate community-acquired respiratory tract infections. These include infection with Streptococcus pneumoniae (both penicillin- and macrolide-resistant strains) as well as ß-lactamase–producing strains of Haemophilus influenzae and Moraxella catarrhalis(5, 6). Telithromycin is also active in vitro against Mycoplasma pneumoniae and Chlamydophilia pneumoniae(7). While telithromycin demonstrates potent in vitro activity against other respiratory pathogens (such as …