Roxithromycin is a semi-synthetic derivative of the macrolide antibiotic erythromycin that includes an N-oxime side chain on the lactone ring, with antibacterial and anti-malarial activities. Roxithromycin binds to the subunit 50S of the bacterial ribosome, which inhibits bacterial protein synthesis and leads to inhibition of bacterial cell growth and replication. Hepatic. Roxithromycin is only partially metabolised, more than half the parent compound being excreted unchanged. Three metabolites have been identified in urine and faeces: the major metabolite is descladinose roxithromycin, with N-mono and N-di-demethyl roxithromycin as minor metabolites. The respective percentage of roxithromycin and these three metabolites is similar in urine and faeces. Roxithromycin prevents bacteria from growing, by interfering with their protein synthesis. Roxithromycin binds to the subunit 50S of the bacterial ribosome, and thus inhibits the translocation of peptides. Roxithromycin has similar antimicrobial spectrum as erythromycin, but is more effective against certain gram-negative bacteria, particularly Legionella pneumophila. | 
