Ketolides block protein synthesis by binding to ribosomal subunits and may also inhibit the formation of newly forming ribosomes. According to a recent study comparing the action of the classic macrolides erythromycin and azithromycin with ketolides, which are used to treat serious infections, the more powerful drugs (ketolides) were the more "leaky" in blocking the production of proteins. The researchers were surprised to discover that ketolides, which are known to be better antibiotics, allow for many more proteins to be made compared to the older, less efficient macrolides. As a result, it is now believed that allowing cells to make some proteins could be much more damaging for a microbe than not letting it make any proteins at all. The findings may point the way to better and more potent antibiotics.
Ketolides are used to treat community-acquired bacterial pneumonia. Other respiratory tract infections were removed as indications when it was recognized that use of telithromycin can result in hepatitis and liver failure.