Comparison of macrolide antibiotics.

Macrolides have been in use since the early 1950s. In recent years new macrolides have been developed to try to overcome the problems associated with erythromycin. In general they have fairly similar in-vitro activity, although azithromycin has superior activity against Haemophilus influenzae and some Gram-negative organisms. Clarithromycin shows superior in-vitro activity against Legionella spp. and against the type strain of Chlamydia pneumoniae. The pharmacology of macrolides produces many interpretive problems, and macrolides show marked variation in their pharmacokinetic parameters, tissue affinity and intracellular penetration. Newer macrolides such as clarithromycin, roxithromycin, dirithromycin and azithromycin only need to be taken once or twice a day, which is likely to improve patient compliance. Few objective side-effect studies have been performed with the newer macrolides. Clinical efficacy studies are essential to elucidate the significance of the complex pharmacology of macrolides.