A macrolide antibiotic; inhibits 50S ribosome activity; active against a host of bacterial genera, including Streptococcus, Staphylococcus, and Haemophilus (MIC90s = 0.015-2.0 mg/l); dose-dependently inhibits the growth of S. aureus in a mouse model of thigh infection at 10-40 mg/kg; inhibits CYP3A4 (IC50s = 33 and 27.3 μM for α-hydroxytriazolam and 4-hydroxytriazolam formation, respectively)