Tobramycin
生产企业：Alcon laboratories inc, Akorn inc，另有 16 家
Tobramycin is an aminoglycoside antibiotic used to treat cystic fibrosis-associated bacterial, lower respiratory tract, urinary tract, eye, skin, bone, and skin structure infections.
Tobramycin is an aminoglycoside antibiotic used to treat cystic fibrosis-associated bacterial, lower respiratory tract, urinary tract, eye, skin, bone, and skin structure infections.
Tobramycin is a 4,6-disubstituted 2-deoxystreptamine (DOS) ring-containing aminoglycoside antibiotic with activity against various Gram-negative and some Gram-positive bacteria. The mechanism of action of tobramycin has not been unambiguously elucidated, and some insights into its mechanism rely on results using similar aminoglycosides. In general, like other aminoglycosides, tobramycin is bactericidal and exhibits both immediate and delayed killing, which are attributed to different mechanisms, as outlined below. Aminoglycosides are polycationic at physiological pH, such that they readily bind to bacterial membranes ("ionic binding"); this includes binding to lipopolysaccharide and phospholipids within the outer membrane of Gram-negative bacteria and to teichoic acid and phospholipids within the cell membrane of Gram-positive bacteria. This binding displaces divalent cations and increases membrane permeability, which allows aminoglycoside entry. Additional aminoglycoside entry ("energy-dependent phase I") into the cytoplasm requires the proton-motive force, allowing access of the aminoglycoside to its primary intracellular target of the bacterial 30S ribosome. Mistranslated proteins produced as a result of aminoglycoside binding to the ribosome (see below) integrate into and disrupt the cell membrane, which allows more of the aminoglycoside into the cell ("energy-dependent phase II"). Hence, tobramycin and other aminoglycosides have both immediate bactericidal effects through membrane disruption and delayed bactericidal effects through impaired protein synthesis; observed experimental data and mathematical modelling support this two-mechanism model. Inhibition of protein synthesis was the first recognized effect of aminoglycoside antibiotics. Structural and cell biological studies suggest that aminoglycosides bind to the 16S rRNA in helix 44 (h44), near the A site of the 30S ribosomal subunit, altering interactions between h44 and h45. This binding also displaces two important residues, A1492 and A1493, from h44, mimicking normal conformational changes that occur with successful codon-anticodon pairing in the A site. Overall, aminoglycoside binding has several negative effects, including inhibiting translation initiation and elongation and ribosome recycling. Recent evidence suggests that the latter effect is due to a cryptic second binding site situated in h69 of the 23S rRNA of the 50S ribosomal subunit. Also, by stabilizing a conformation that mimics correct codon-anticodon pairing, aminoglycosides promote error-prone translation; mistranslated proteins can incorporate into the cell membrane, inducing the damage discussed above. Although direct mutation of the 16S rRNA is a rare resistance mechanism, due to the gene being present in numerous copies, posttranscriptional 16S rRNA modification by 16S rRNA methyltransferases (16S-RMTases) at the N7 position of G1405 or the N1 position of A1408 are common resistance mechanisms in aminoglycoside-resistant bacteria. These mutants also further support the proposed mechanism of action of aminoglycosides. Direct modification of the aminoglycoside itself through acetylation, adenylation, and phosphorylation by aminoglycoside-modifying enzymes (AMEs) are also commonly encountered resistance mutations. Finally, due to the requirement for active transport of aminoglycosides across bacterial membranes, they are not active against obligately anaerobic bacteria.
Inhaled tobramycin is indicated for the management of cystic fibrosis patients with Pseudomonas aeruginosa, but is not recommended in patients under six years of age, those with forced expiratory volume in 1 second (FEV) <25 or >80% predicted, or in those with Burkholderia cepacia. Tobramycin applied topically to the eyes is indicated for the treatment of external eye (and adjoining structure) infections by susceptible bacteria. Tobramycin injection is indicated in adult and pediatric patients for the treatment of serious bacterial infections, including septicemia (caused by P. aeruginosa, Escherichia coli, and Klebsiella spp.), lower respiratory tract infections (caused by P. aeruginosa, Klebsiella spp., Enterobacter spp., Serratia spp., E. coli, and Staphylococcus aureus, both penicillinase and non-penicillinase-producing strains), serious central-nervous-system infections (meningitis, caused by susceptible organisms), intra-abdominal infections including peritonitis (caused by E. coli, Klebsiella spp., and Enterobacter spp.), skin, bone, and skin structure infections (caused by P. aeruginosa, Proteus spp., E. coli, Klebsiella spp., Enterobacter spp., Serratia spp. and S. aureus), and complicated and recurrent urinary tract infections (caused by P. aeruginosa, Proteus spp., E. coli, Klebsiella spp., Enterobacter spp., Serratia spp., S. aureus, Providencia spp., and Citrobacter spp.). Aminoglycosides, including tobramycin, should generally not be used in uncomplicated urinary tract infections or staphylococcal infections unless less toxic antibiotics cannot be used and the bacteria in question are known to be sensitive to aminoglycosides. As with all antibiotics, tobramycin use should be limited to cases where bacterial infections are known or strongly suspected to be caused by sensitive organisms, and the possible emergence of resistance should be monitored closely.
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