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Vancomycin inhibits synthesis of bacterial cell membranes. Unlike beta-lactam antibiotics, which inhibit the third stage of peptidoglycan synthesis, vancomycin affects the second stage of creating bacterial cell membranes. Vancomycin inhibits the reaction in which the repeating unit of the cell membrane is separated from the cytoplasmic membrane-bound phospholipids, and binds with the already existing peptidoglycan. It also damages protoplasts by affecting the cytoplasmic membrane through the inhibition of RNA synthesis. Vancomycin is active only with respect to Gram-positive bacteria. It is the most powerful of all of the known antibiotics with respect to S. aureus and Staphylococcus epidermidus, including methicillin- and cephalosporin-resistant strains.

Resistance of Gram-negative organisms (such as mycobacteria), fungi, virii, and prota-zoans to vancomycin occurs because the barrier is impermeable to the drug, which is ensured by the outer membrane. Resistance of Gram-positive organisms to vancomycin is rarely observed.

Vancomycin is used for serious bacterial infections caused by microorganisms sensitive to this drug when penicillins and cephalosporins are ineffective for diseases such as sepsis, endocarditis, pneumonia, pulmonary abscess, osteomyelitis, meningitis, and enterocolitis, or when penicillins and cephalosporins cannot be tolerated by patients. Vancomycin is the drug of choice for infections caused by methicillin-resistant forms of S. aureus, S. epider-midus, and other coagulase-negative staphylococci, as well as for endocarditis, diphtherioid infections, and for patients very sick with colitis caused by C. difficile. A synonym of this drug is vancocin.

Rifampicin: Rifampicin, 5,6,9,17,19,21-hexahydroxy-23-methoxy-2,4,12,16,18,20,22-hep-tamethyl-8-[N-(4-methyl-1-piperazinyl)-formimidoyl]-2,7-(epoxypentadeca-1,11,13-trien-imino)-naphtho-[2,1-b] furan-1,11(2H)dion-21-acetate (32.7.8).

Rifampicin is a semisynthetic derivative of rifamicin B, a macrolactam antibiotic and one of more than five antibiotics from a mixture of rifamicins A, B, C, D, and E, which is called a rifamicin complex, which is produced by actinomycetes Streptomyces mediteranei (Nocardia mediteranei). It was introduced into medical practice in 1968. Synthesis of rifampicin begins with an aqueous solution of rifamicin, which under the reaction conditions is oxidized to a new derivative of rifamicin S (32.7.4), with the intermediate formation of rifamicin O (32.7.3). Reducing the quinone structure of this product with hydrogen using a palladium on carbon catalyst gives rifamicin SV (32.7.5). The resulting product undergoes aminomethylation by a mixture of formaldehyde and pyrrolidine, giving 3-pyrrolidi-nomethylrifamicin SV (32.7.6). Oxidizing the resulting product with lead tetracetate to an enamine and subsequent hydrolysis with an aqueous solution of ascorbic acid gives 3-formylrifamicin SV (32.7.7). Reacting this with 1-amino-4-methylpiperazine gives the desired rifampicin (32.7.8) [331-334].

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