Ketolide

Ketolides are derived from erythromycin by substituting the cladinose sugar with a keto-group and attaching a cyclic carbamate group in the lactone ring.

Moreover, ketolides are effective against macrolide-resistant bacteria, due to their ability to bind at two sites at the bacterial ribosome as well as having a structural modification that makes them poor substrates for efflux-pump mediated resistance.

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.

Other respiratory tract infections were removed as indications when it was recognized that use of telithromycin can result in hepatitis and liver failure.