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Chapter: Essential pharmacology : Macrolide, Lincosamide, Glycopeptide And Other Antibacterial Antibiotics; Urinary Antiseptics

Linezolid : This is the first member of a new class of synthetic AMAs ‘Oxazolidinones’ which has become available for the treatment of resistant gram-positive coccal (aerobic and anaerobic) and bacillary infections.





This is the first member of a new class of synthetic AMAs ‘Oxazolidinones’ which has become available for the treatment of resistant gram-positive coccal (aerobic and anaerobic) and bacillary infections. It is active against MRSA and some VRSA, VRE, penicillin-resistant Strep. pyogenes, Strep. viridans and Strep. pneumoniae, M. tuberculosis, Corynebacterium, Listeria, Clostridia and Bact. fragilis. It is primarily bacteriostatic, but can exert cidal action against some streptococci, pneumococci and B. fragilis. Gram-negative bacteria are not affected.


Linezolid inhibits bacterial protein synthesis by acting at an early step and a site different from that of other AMAs. It binds to the 23 S fraction of the 50S ribosome and interferes with formation of the ternary N-formyl-methioninet-RNA (tRNAfMet) 70S initiation complex. Binding of linezolid distorts the tRNA binding site overlapping both 50S and 30S ribosomal subunits and stops protein synthesis before it starts. As such, there is no cross resistance with any other class of AMAs.


Linezolid is rapidly and completely absorbed orally, partly metabolized nonenzymatically and excreted in urine. Plasma t½ is 5 hrs. Dose modification has not been necessary in renal insufficiency.


Linezolid has been used for uncomplicated and complicated skin and soft tissue infections, community and hospital acquired pneumonias, bacteraemias and other drug-resistant gram-positive infections by oral and i.v. routes with 83–94% cure rates. However, to prevent emergence of resistance to this valuable drug, use should be restricted to serious hospital-acquired pneumonias, febrile neutropenia, wound infections and others caused by multi-drugresistant gram-positive bacteria susch as VRE, vancomycin resistant-MRSA, multi-resistant S. pneumoniae, etc. Being bacteriostatic, it is not suitable for treatment of enterococcal endocarditis.


Dose: 600 mg BD, oral/ i.v.; LIZOLID 600 mg tab; LINOX 600 mg tab, 200 mg/100 ml i.v. infusion.


Side effects to linezolid have been few; mostly mild abdominal pain and bowel upset. Occasionally, rash, pruritus, headache, oral/ vaginal candidiasis have been reported. Neutropenia and thrombocytopenia are infrequent and usually mild. Because linezolid is a MAO inhibitor, interactions with adrenergic/serotonergic drugs and excess dietary tyramine are expected. No cytochrome P450 enzyme related interactions seem likely.




It is a recently developed combination of two semisynthetic pristinamycin antibiotics which together exert synergistic inhibition of bacterial protein synthesis. It is active against most gram-positive cocci including MRSA, some VRSA and some VRE; as well as certain Neisseria, Legionella and Chlamydia pneumoniae. The combination is bactericidal against strepto and staphylococci but bacteriostatic against E. faecium.


It is being used in Europe, USA and some other countries for serious nosocomial MRSA, VRE and other resistant gram positive infections.




This topically used antibiotic obtained from a species of Pseudomonas is active mainly against gram-positive bacteria, including Strep. pyogenes (penicillin sensitive/resistant), Staph aureus. MRSA, etc. It inhibits bacterial protein synthesis by blocking the production of tRNA for isoleucin. As such, no cross resistance with any other antibiotic is seen. Though primarily bacteriostatic, high concentrations applied topically may be bactericidal. It is indicated in furunculosis, folliculitis, impetigo, infected insect bites and small wounds. Local itching, irritation and redness may occur.


BACTROBAN, MUPIN, TBACT 2% oint. for topical application thrice daily.


Fusidic acid


It is a narrow spectrum steroidal antibiotic, blocks bacterial protein synthesis and is active against penicillinase producing Staphylococci and few other gram-positive bacteria. It is used only topically for boils, folliculitis, sycosis barbae and other cutaneous infections.


FUCIDINL, FUCIBACT, FUSIDERM; 2% oint. and cream.


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