Azithromycin: an interim analysis.

Azithromycin, a novel azalide antibiotic structurally related to erythromycin, has been shown by in vitro studies to have similar activity to erythromycin against Gram-positive pathogens but additionally to have increased activity against some Gram-negative bacteria, notably Haemophilus influenzae. Azithromycin achieves excellent concentrations in tissues, polymorphonuclear leucocytes and alveolar macrophages, and has a prolonged tissue elimination half-life. These properties suggest that short-course, once-daily treatment regimens will be appropriate for a variety of bacterial infections, including those of the respiratory tract, skin and soft tissues. The results of a series of clinical trials using such a regimen are reviewed. It is concluded that azithromycin is clinically and bacteriologically effective in these indications and is well tolerated when compared with regimens using standard antibiotics.