Clarithromycin is a macrolide antibacterial whose spectrum of action includes abounding gram-positive (Staphylococcus aureus, S. pneumoniae, and S. pyogenes) and gram-negative aerobic bacilli (Haemophilus influenzae, H. parainfluenzae, and Moraxella catarrhalis), abounding anaerobic bacteria, some mycobacteria, and some added bacilli including Mycoplasma, Ureaplasma, Chlamydia, Toxoplasma, and Borrelia. Added aerobic bacilli that clarithromycin has action adjoin cover C. pneumoniae and M. pneumoniae. Clarithromycin has an in-vitro action that is agnate or greater than that of erythromycin adjoin erythromycin-susceptible organisms.
Clarithromycin is usually bacteriostatic, but may be antibacterial depending on the animal and the biologic concentration.
Clarithromycin is aboriginal metabolized to 14-OH clarithromycin, which is alive and works synergistically with its ancestor compound. Like added macrolides, it again penetrates bacilli corpuscle bank and reversibly binds to area V of the 23S ribosomal RNA of the 50S subunit of the bacterial ribosome, blocking about-face of aminoacyl transfer-RNA and polypeptide synthesis. Clarithromycin aswell inhibits the hepatic microsomal CYP3A4 isoenzyme and P-glycoprotein, an energy-dependent biologic address pump.