The new macrolactones: clarithromycin (Biaxin) and azithromycin (Zithromax).

Clarithromycin and azithromycin are new macrolactone antibiotics which offer several advantages over erythromycin such as increased bioavailability secondary to better acid stability, excellent tissue and intracellular distribution, extended half-lives allowing for once-daily or twice-daily dosing, lower gastrointestinal intolerance, and greater microbiological activity against selected organisms (eg, H. influenzae). These new agents are significantly more expensive than erythromycin.