Figure 1Stylized cells depicting the transport, metabolism and mechanism of action of the macrolide antibiotics erythromycin, clarithromycin, and azithromycin
The bacteriostatic and bactericidal properties of macrolide antibiotics result from inhibition of the 50S subunit of the 70S bacterial ribosome. Erythromycin is degraded in low pH environments, such as in the stomach, whereas clarithromycin and azithromycin are more acid stable, leading to increased bioavailability. Erythromycin and clarithromycin interact more extensively with drug transporters and metabolizing enzymes than does azithromycin due to different chemical properties. An interactive version of this pathway is available at PharmGKB [https://www.pharmgkb.org/pathway/PA166160731].