Clarithromycin, a new semisynthetic macrolide, is lipophilic and achieves concentrations in tissue that are generally 10 times greater than concentrations achieved in serum. Its binding to serum proteins is low and reversible.
Clarithromycin hasin vitroandin vivoactivity against a variety of Gram-positive and Gram-negative bacteria,Mycoplasma, Chlamydiaand mycobacteria. 14-Hydroxyclarithromycin, the major metabolite of clarithromycin in humans, is generally as active as clarithromycin against these organisms but is more activein vitroandin vivothan clarithromycin againstHaemophilus influenzae.Organisms resistant to erythromycin by plasmid or transposon-encoded methylase, macrolide-lincosamide-streptogramin resistance, are also resistant to clarithromycin. Unlike older macrolides, however, clarithromycin hasin vitroandin vivoactivity against atypical mycobacteria. The antimicrobial activities of clarithromycin and 14-hydroxyclarithromycin are reviewed in this article.