Telithromycin is a semisynthetic 14-membered macrolide antibiotic and erythromycin derivative that binds to the 50S subunit of the 70S bacterial ribosome, inhibits bacterial protein synthesis, and exhibits antimicrobial activity against a wide range of gram-positive and gram-negative bacteria for the treatment of mild to moderate respiratory infections.

The in vitro antimicrobial activity of Telithromycin was determined using Methods such as broth microdilution, agar dilution, and E-test Methods. MIC distribution was homogeneous (MIC range, 0.003 to 0.25 μg/ml)[1]. However, its MIC50 and MIC90 against Mycobacterium avium complex were both greater than 16 μg/ml, indicating weaker in vitro antimicrobial activity [2].

In mouse models, oral Telithromycin (3-26 mg/kg) demonstrated excellent efficacy against erythromycin-resistant sepsis and significant antibacterial activity against a range of pathogens. In the erythromycin-resistant *Streptococcus pneumoniae* model, the ED50 of Telithromycin was 6.5 mg/kg, comparable to the efficacy of azithromycin. At a dose of 100 mg/kg, the plasma Cmax reached 8.5 mg/L, with lung concentrations of 13.3 μg/g. The volume of distribution was similar to that in humans, with plasma and lung tissue half-lives of 2.5 hours and 2.8 hours, respectively[3].