The chemistry, mechanism of action, antimicrobial spectrum, pharmacokinetics, clinical efficacy, adverse effects, drug interactions, and dosage and administration of
clarithromycin and
azithromycin are described.
Clarithromycin and
azithromycin are new
macrolide antibiotics that are similar in structure to
erythromycin. Compared with
erythromycin,
clarithromycin demonstrates increased activity against Staphylococcus aureus, streptococci, Legionella pneumophila, Moraxella catarrhalis, and Chlamydia trachomatis.
Clarithromycin also has in vitro activity against Mycobacterium avium complex (MAC) and Toxoplasma gondii.
Azithromycin has increased gram-negative activity compared with
erythromycin, including activity against Haemophilus influenzae, while maintaining activity against gram-positive organisms.
Azithromycin also has activity against sexually transmitted organisms including Chlamydia trachomatis. The pharmacokinetic profiles of
clarithromycin and
azithromycin are characterized by good oral bioavailability, excellent tissue penetration and persistence, and long elimination half-lives, which allow for once-daily or twice-daily dosing. Initial data show that
clarithromycin and
azithromycin are effective for the treatment of upper-respiratory-tract and lower-
respiratory-tract infections and
infections of the skin and skin structures.
Azithromycin has been shown to be effective for the treatment of
sexually transmitted diseases caused by Chlamydia trachomatis.
Clarithromycin and
azithromycin have been used to treat MAC and Toxoplasma
infections in patients with the
acquired immunodeficiency syndrome. The most frequently reported adverse effects for both agents have been
nausea,
diarrhea, and
abdominal pain. Oral formulations of
clarithromycin and
azithromycin have recently been approved by the FDA.
Clarithromycin and
azithromycin are new
macrolide antibiotics that have potential advantages over
erythromycin; however, the role of these agents will be better defined as results of more ongoing trials become available for evaluation.