Tobramycin was initially identified as part of a broad-spectrum antibiotic complex, nebramycin, which was first isolated in 1967 by Eli Lilly and Company. One component of this complex, first designated as Factor 6, subsequently became tobramycin, since it was derived from Streptomyces tenebrarius. Tobramycin is most similar in structure to members of the kanamycin group of aminoglycosides.
Tobramycin inhibits protein synthesis through binding with the 30S ribosomal subunit of prokaryotic ribosomes. The clinically relevant antibacterial spectrum of tobramycin includes staphylococci, notably Staphylococcus aureus and Staphylococcus epidermidis. All streptococci, including Streptococcus pneumoniaeand enterococci are resistant.
Tobramycin is active against many aerobic and facultative gram-negative bacilli, including Enterobacteriaceae, Pseudomonas aeruginosa (P. aeruginosa), and Acinetobacter spp. Although active in vitro, tobramycin is not used clinically for infections caused by Haemophilus spp. and Legionella spp. due to low intracellular concentration. Tobramycin is also not the preferred aminoglycoside for mycobacterial infections or infections caused by Yersinia spp. and Francisella spp. As with all aminoglycosides, tobramycin requires aerobic metabolism to exert its effect, thus it does not have activity against anaerobic bacteria.
Treatment of serious Gram-negative bacterial infections and infections caused by staphylococci when penicillins or other less toxic drugs are contraindicated. Management of cystic fibrosis patients with Pseudomonas aeruginosa.
Mechanism of Action Inhibits protein synthesis in bacteria at level of 30S ribosome.
Spectrum: Most aminoglycosides notable for activityagainst: Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Proteus,Serratia, Acinetobacter, Staphylococcus aureus. In treatment of enterococcalinfections, synergy with a penicillin is required.
Hypersensitivity; Most parenteral products contain bisulfites and should be avoided in patients with known intolerance; Cross-sensitivity among aminoglycosides may occur.
Use Cautiously in: Renal impairment (dose adjustments necessary; blood level monitoring useful in preventing ototoxicity and nephrotoxicity); Hearing impairment; Difficulty in assessing auditory and vestibular function; age-related renal impairment; Neonates (risk of neuromuscular blockade; difficulty in assessing auditory and vestibular function; immature renal function); Neuromuscular diseases such as myasthenia gravis; Obese patients (dosage should be based on ideal body weight);OB: May cause congenital deafness.
Adverse Reactions/Side Effects
EENT: ototoxicity (vestibular and cochlear) Inhalation only, tinnitus, voice alteration.
GI: PSEUDOMEMBRANOUS COLITIS.
F and E: hypomagnesemia. MS: muscle paralysis (high parenteral doses).
Resp: Inhalation only bronchospasm, wheezing.
Misc: hypersensitivity reactions.