Ketolide

Telithromycin

Ketolidesareantibioticsbelonging to themacrolidegroup. Ketolides are derived fromerythromycinby substituting thecladinosesugar with aketo-groupand attaching a cycliccarbamategroup in thelactonering.These modifications give ketolides much broader spectrum than other macrolides. Moreover, ketolides are effective againstmacrolide-resistant bacteria,due to their ability to bind at two sites at the bacterialribosomeas well as having a structural modification that makes them poor substrates for efflux-pump mediated resistance.

Ketolides blockprotein synthesisby 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 andazithromycinwith 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.

The only ketolide on the market at this moment istelithromycin,which is sold under the brand name ofKetek.Other ketolides in development includecethromycinandsolithromycin.

Medical uses

Ketolides are used to treat community-acquiredbacterial pneumonia.Otherrespiratory tract infectionswere removed as indications when it was recognized that use oftelithromycincan result inhepatitisandliver failure.