Lincosamides

Lincosamides (eg. lincomycin, clindamycin) are a class of drugs which bind to the 23s portion of the 50S subunit of bacterial ribosomes and inhibit early elongation of peptide chain by inhibiting transpeptidase reaction. In this sense they have a similar action to macrolides.

History and uses
The first lincosamide to be discovered was lincomycin, which is a true antibiotic (one occurring naturally rather than being synthetic), from "Streptomyces lincolnensis".

Lincomycin has been superseeded by clindamycin, which exhibits improved antibacterial activity. Clindamycin also exhibits some activity against parasitic protozoa, and has been used in toxoplasmosis and malaria.

They are normally used to treat staphylococci and streptococci, and have proved useful in treating Bacteroides fragili and some other anaerobes.

Resistance
Target bacteria may alter the drug's binding site (similar to resistance found in macrolides and streptogramins). The resistance mechanism is methylation of the 23s binding site. If this occurs then the bacteria are resistant to both the macrolides and the lincosamides. Also, enzymatic inactivation of clindamycin has been described (rare).

Formulation
The lincosamides, as the hydrochloride salt, are bitter to taste, so for oral formulation they are given as the palmitate esters, or formulated in capsules. Clindamycin is given intravenously as clindamycin phosphate, which is then converted into active clindamycin wihin the body.

Pharmacodynamics
These are bacteriostatic drugs and antagonists of macrolides and streptogramins.