Clarithromycin is an
acid-stable orally administered
macrolide antimicrobial
drug, structurally related to
erythromycin. It has a broad spectrum of antimicrobial activity, similar to that of
erythromycin and inhibits a range of Gram-positive and Gram-negative organisms, atypical pathogens and some anaerobes. Significantly,
clarithromycin demonstrates greater in vitro activity than
erythromycin against certain pathogens including Bacteroides melaninogenicus, Chlamydia pneumoniae, Chlamydia trachomatis, Mycobacterium chelonae subspecies--chelonae and--abscessus, Mycobacterium leprae, Mycobacterium marinum, Mycobacterium avium complex, Legionella spp. and, when combined with its 14-hydroxy metabolite, against Haemophilus influenzae. However, bacterial strains resistant to
erythromycin are also generally resistant to
clarithromycin. The antimicrobial activity of
clarithromycin appears to be enhanced by the formation in vivo of the microbiologically active 14-hydroxy metabolite. In combination, additive or synergistic activity against a variety of pathogens including Haemophilus influenzae, Moraxella catarrhalis, Legionella species (principally Legionella pneumophila) and various staphylococci and streptococci has been demonstrated.
Clarithromycin has a superior pharmacokinetic profile to that of
erythromycin, allowing the benefits of twice daily administration with the potential for increased compliance among outpatients where a more frequent regimen for
erythromycin might otherwise be indicated. The clinical efficacy of
clarithromycin has been confirmed in the treatment of
infections of the lower and upper respiratory tracts (including those associated with atypical pathogens), skin/soft tissues, and in paediatrics.
Clarithromycin was as effective as
erythromycin and other appropriate drugs including
beta-lactams (
penicillins and
cephalosporins) in some of the above
infections. A most promising indication for
clarithromycin appears to be in the treatment of immunocompromised patients infected with M. avium complex, M. chelonae sp. and Toxoplasma sp. Small initial trials in this setting reveal
clarithromycin alone or in combination with other antimicrobials to be effective in the eradication or amelioration of these
infections. Noncomparative studies have provided preliminary evidence for the effectiveness of
clarithromycin in the treatment of
infections of the urogenital tract, oromaxillofacial and ophthalmic areas. However, the promising in vitro and preliminary in vivo activity of
clarithromycin against Mycobacterium leprae and Helicobacter pylori warrant further clinical trials to assess its efficacy in patients with these
infections. Despite the improved pharmacokinetic profile and in vitro antimicrobial activity of
clarithromycin over
erythromycin, comparative studies of patients with
community-acquired infections reveal the 2 drugs to be of equivalent efficacy. However,
clarithromycin demonstrates greater tolerability, principally by inducing fewer gastrointestinal disturbances.(ABSTRACT TRUNCATED AT 400 WORDS)