The newer macrolides. Azithromycin and clarithromycin.

Azithromycin and clarithromycin are structural analogues of erythromycin that have similar mechanisms of action. The newer macrolides have several distinct advantages over erythromycin, including improved oral bioavailability; longer half-life, allowing once or twice daily administration; higher tissue concentrations; and fewer gastrointestinal adverse effects. Clarithromycin and azithromycin also have enhanced antimicrobial activity. The clinical efficacy of the newer macrolides has been similar to erythromycin for the treatment of upper and lower respiratory tract and skin and soft tissue infections. New therapeutic roles include the use of azithromycin for C. trachomatis infections and the inclusion of clarithromycin or azithromycin as part of therapeutic regimens for disseminated MAC infections in HIV-infected patients. Further clinical trials are needed to determine the optimal roles for and uses of these new macrolides.