Last updated

Tobramycin 1lc4.png
Clinical data
Trade names Nebcin, Tobrex, Tobi, others
Other names47663, SPRC-AB01
AHFS/ Monograph
MedlinePlus a682660
License data
Routes of
Intravenous, intramuscular, inhalation, ophthalmic
ATC code
Legal status
Legal status
  • UK: POM (Prescription only) [3]
  • US: WARNING [4] Rx-only
  • EU:Rx-only
  • In general: ℞ (Prescription only)
Pharmacokinetic data
Protein binding Not bound [5]
Metabolism Not metabolized
Elimination half-life 2–3 hrs
Excretion Exclusively via kidneys
  • (2S,3R,4S,5S,6R)-4-amino-2-{[(1S,2S,3R,4S,6R)-4,6-diamino-3-{[(2R,3R,5S,6R)-3-amino-6-(aminomethyl)-5-hydroxyoxan-2-yl]oxy}-2-hydroxycyclohexyl]oxy}-6-(hydroxymethyl)oxane-3,5-diol
CAS Number
PubChem CID
PDB ligand
CompTox Dashboard (EPA)
ECHA InfoCard 100.046.642 OOjs UI icon edit-ltr-progressive.svg
Chemical and physical data
Formula C18H37N5O9
Molar mass 467.520 g·mol−1
3D model (JSmol)
  • C1[C@@H]([C@H]([C@@H]([C@H]([C@@H]1N)O[C@@H]2[C@@H]([C@H]([C@@H]([C@H](O2)CO)O)N)O)O)O[C@@H]3[C@@H](C[C@@H]([C@H](O3)CN)O)N)N
  • InChI=1S/C18H37N5O9/c19-3-9-8(25)2-7(22)17(29-9)31-15-5(20)1-6(21)16(14(15)28)32-18-13(27)11(23)12(26)10(4-24)30-18/h5-18,24-28H,1-4,19-23H2/t5-,6+,7+,8-,9+,10+,11-,12+,13+,14-,15+,16-,17+,18+/m0/s1 Yes check.svgY

Tobramycin is an aminoglycoside antibiotic derived from Streptomyces tenebrarius that is used to treat various types of bacterial infections, particularly Gram-negative infections. It is especially effective against species of Pseudomonas . [6]


It was patented in 1965, and approved for medical use in 1974. [7] It is on the World Health Organization's List of Essential Medicines. [8] In 2021, it was the 299th most commonly prescribed medication in the United States, with more than 500,000 prescriptions. [9] [10]

Medical uses

Like all aminoglycosides, tobramycin does not pass the gastro-intestinal tract, so for systemic use it can only be given intravenously or by injection into a muscle. Eye drops and ointments (tobramycin only, Tobrex, or combined with dexamethasone, sold as Tobradex) and nebulised formulations both have low systemic absorption. The formulation for injection is branded Nebcin. The nebulised formulation (brand name Tobi) is indicated in the treatment of exacerbations of chronic infection with Pseudomonas aeruginosa in people diagnosed with cystic fibrosis. [11] [12]

Tobramycin eye drops (with or without dexamethasone) are indicated in the treatment of superficial infections of the eye, such as bacterial conjunctivitis. [13] [14] [15] [16]

Tobramycin, in its injectable form, is also indicated for various severe or life-threatening infections caused by susceptible strains: sepsis, meningitis, lower respiratory tract infections, intra-abdominal infections, skin infections, bone infections, and skin structure infections, complicated and recurrent urinary tract infections. [17] [3]

Spectrum of susceptibility

Tobramycin has a narrow spectrum of activity and is active against Gram-positive Staphylococcus aureus and various Gram-negative bacteria. [17] Clinically, tobramycin is frequently used to eliminate Pseudomonas aeruginosa in cystic fibrosis patients. [ citation needed ]The following represents the minimum inhibitory concentration (MIC) susceptibility data for a few strains of Pseudomonas aeruginosa:

The MIC for Klebsiella pneumoniae, KP-1, is 2.3±0.2 µg/mL at 25 °C [unpublished][ clarification needed ].[ medical citation needed ]


Tobramycin is contraindicated in people with hypersensitivity against aminoglycoside antibiotics. [19] The Infusion is also contraindicated in people with myasthenia gravis. [5]

Side effects

Like other aminoglycosides, a major side effect for tobramycin is ototoxicity or a loss of equilibrioception, or both in genetically susceptible individuals. [20] Other side effects include nephrotoxicity, neuromuscular toxicity, and hypersensitivity reactions. [21] Nephrotoxicity can be particularly worrisome when multiple doses accumulate over the course of a treatment [22] or when the kidney concentrates urine by increasing tubular reabsorption during sleep. Adequate hydration may help prevent excess nephrotoxicity and subsequent loss of renal function. [23] For these reasons parenteral tobramycin needs to be carefully dosed by body weight, and its serum concentration monitored. Tobramycin is thus said to be a drug with a narrow therapeutic index.[ citation needed ]


Muscle relaxants and diethylether can add to the neuromuscular blocking effects of tobramycin. [5]

Methoxyflurane, when used as an inhalational anesthetic, can aggravate the nephrotoxic effects of injected tobramycin. Likewise, combining injected tobramycin with other nephrotoxic or ototoxic drugs can lead to more adverse effects; examples include amphotericin B, ciclosporin, cisplatin, vancomycin, and the diuretic furosemide. Other diuretics can also increase the risk for side effects because they raise tobramycin concentrations in the body fluids. [5]

Combining tobramycin with betalactam antibiotics can be desirable because of their synergistic effects. However, when they are given through the same drip, as well as in people with reduced kidney function, they can react with each other to form antibiotically inactive amides. [5]


Mechanism of action

Tobramycin works by binding to a site on the bacterial 30S and 50S ribosome, preventing formation of the 70S complex. [24] As a result, mRNA cannot be translated into protein, and cell death ensues. [25] Tobramycin also binds to RNA-aptamers, [26] artificially created molecules to bind to certain targets. However, there seems to be no indication that Tobramycin binds to natural RNAs or other nucleic acids.[ citation needed ]

The effect of tobramycin can be inhibited by metabolites of the Krebs (TCA) cycle, such as glyoxylate. These metabolites protect against tobramycin lethality by diverting carbon flux away from the TCA cycle, collapsing cellular respiration, and thereby inhibiting Tobramycin uptake and thus lethality. [27]


Tobramycin is not absorbed in the gut. When given as infusion, it is distributed in the extracellular fluid. It can accumulate in the kidney's tubular cells and in the lymph of the inner ear. Only low concentrations reach the central nervous system and breast milk. Tobramycin passes the placenta: in the fetus, 20% of the mother's concentrations have been measured. [5]

The substance is neither bound to plasma proteins, nor is it metabolized. It is excreted in unchanged form via the kidneys with a biological half-life of about 2 to 3 hours. Elimination from deep compartments such as the renal cortex follows after 8 to 12 hours. In newborns the half-life is 4.6 hours on average; in those with a low birth weight it is as long as 8.7 hours on average. People with reduced kidney function also have a longer half-life for tobramycin, while in those with severe burns it can be shorter. [5]

Society and culture

Tobramycin was patented in 1965, and approved for medical use in 1974. [7] .

Tobramycin in the form of eye drops is available in Bulgaria, Hungary, the United States, and Canada by prescription only, whereas in the other countries it may be available over the counter.[ citation needed ]

Tobrex eye drops are a 0.3% tobramycin sterile ophthalmic solution produced by Alcon Pharmaceuticals. Benzalkonium chloride 0.01% is added to Tobrex as a preservative.[ citation needed ]

In Egypt, tobramycin (in the form of eye drops) is sold under the brand Tobrin, produced by EIPICo.[ citation needed ]

Tobramycin is on the World Health Organization's List of Essential Medicines. [8]

In 2021, tobramycin was the 299th most commonly prescribed medication in the United States, with more than 500,000 prescriptions. [9]

Related Research Articles

<span class="mw-page-title-main">Chloramphenicol</span> Antibiotic

Chloramphenicol is an antibiotic useful for the treatment of a number of bacterial infections. This includes use as an eye ointment to treat conjunctivitis. By mouth or by injection into a vein, it is used to treat meningitis, plague, cholera, and typhoid fever. Its use by mouth or by injection is only recommended when safer antibiotics cannot be used. Monitoring both blood levels of the medication and blood cell levels every two days is recommended during treatment.

<span class="mw-page-title-main">Vancomycin</span> Antibiotic medication

Vancomycin is a glycopeptide antibiotic medication used to treat a number of bacterial infections. It is used intravenously as a treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infections, and meningitis caused by methicillin-resistant Staphylococcus aureus. Blood levels may be measured to determine the correct dose. Vancomycin is also taken orally as a treatment for severe Clostridium difficile colitis. When taken orally it is poorly absorbed.

<span class="mw-page-title-main">Gentamicin</span> Antibiotic medication

Gentamicin is an antibiotic used to treat several types of bacterial infections. This may include bone infections, endocarditis, pelvic inflammatory disease, meningitis, pneumonia, urinary tract infections, and sepsis among others. It is not effective for gonorrhea or chlamydia infections. It can be given intravenously, by intramuscular injection, or topically. Topical formulations may be used in burns or for infections of the outside of the eye. It is often only used for two days until bacterial cultures determine what specific antibiotics the infection is sensitive to. The dose required should be monitored by blood testing.

<span class="mw-page-title-main">Aminoglycoside</span> Antibacterial drug

Aminoglycoside is a medicinal and bacteriologic category of traditional Gram-negative antibacterial medications that inhibit protein synthesis and contain as a portion of the molecule an amino-modified glycoside (sugar). The term can also refer more generally to any organic molecule that contains amino sugar substructures. Aminoglycoside antibiotics display bactericidal activity against Gram-negative aerobes and some anaerobic bacilli where resistance has not yet arisen but generally not against Gram-positive and anaerobic Gram-negative bacteria.

<span class="mw-page-title-main">Aztreonam</span> Chemical compound

Aztreonam, sold under the brand name Azactam among others, is an antibiotic used primarily to treat infections caused by gram-negative bacteria such as Pseudomonas aeruginosa. This may include bone infections, endometritis, intra abdominal infections, pneumonia, urinary tract infections, and sepsis. It is given by intravenous or intramuscular injection or by inhalation.

<span class="mw-page-title-main">Colistin</span> Antibiotic

Colistin, also known as polymyxin E, is an antibiotic medication used as a last-resort treatment for multidrug-resistant Gram-negative infections including pneumonia. These may involve bacteria such as Pseudomonas aeruginosa, Klebsiella pneumoniae, or Acinetobacter. It comes in two forms: colistimethate sodium can be injected into a vein, injected into a muscle, or inhaled, and colistin sulfate is mainly applied to the skin or taken by mouth. Colistimethate sodium is a prodrug; it is produced by the reaction of colistin with formaldehyde and sodium bisulfite, which leads to the addition of a sulfomethyl group to the primary amines of colistin. Colistimethate sodium is less toxic than colistin when administered parenterally. In aqueous solutions it undergoes hydrolysis to form a complex mixture of partially sulfomethylated derivatives, as well as colistin. Resistance to colistin began to appear as of 2015.

<span class="mw-page-title-main">Carbenicillin</span> Chemical compound

Carbenicillin is a bactericidal antibiotic belonging to the carboxypenicillin subgroup of the penicillins. It was discovered by scientists at Beecham and marketed as Pyopen. It has Gram-negative coverage which includes Pseudomonas aeruginosa but limited Gram-positive coverage. The carboxypenicillins are susceptible to degradation by beta-lactamase enzymes, although they are more resistant than ampicillin to degradation. Carbenicillin is also more stable at lower pH than ampicillin.

<span class="mw-page-title-main">Ceftazidime</span> Antibiotic medication

Ceftazidime, sold under the brand name Fortaz among others, is a third-generation cephalosporin antibiotic useful for the treatment of a number of bacterial infections. Specifically it is used for joint infections, meningitis, pneumonia, sepsis, urinary tract infections, malignant otitis externa, Pseudomonas aeruginosa infection, and vibrio infection. It is given by injection into a vein, muscle, or eye.

<span class="mw-page-title-main">Cefepime</span> Fourth-generation Cephalosporin Antibiotic

Cefepime is a fourth-generation cephalosporin antibiotic. Cefepime has an extended spectrum of activity against Gram-positive and Gram-negative bacteria, with greater activity against both types of organism than third-generation agents. A 2007 meta-analysis suggested when data of trials were combined, mortality was increased in people treated with cefepime compared with other β-lactam antibiotics. In response, the U.S. Food and Drug Administration (FDA) performed their own meta-analysis which found no mortality difference.

<span class="mw-page-title-main">Amikacin</span> Antibiotic medication

Amikacin is an antibiotic medication used for a number of bacterial infections. This includes joint infections, intra-abdominal infections, meningitis, pneumonia, sepsis, and urinary tract infections. It is also used for the treatment of multidrug-resistant tuberculosis. It is used by injection into a vein using an IV or into a muscle.

<span class="mw-page-title-main">Capreomycin</span> Pharmaceutical drug

Capreomycin is an antibiotic which is given in combination with other antibiotics for the treatment of tuberculosis. Specifically it is a second line treatment used for active drug resistant tuberculosis. It is given by injection into a vein or muscle.

<span class="mw-page-title-main">Apramycin</span> Chemical compound

Apramycin is an aminoglycoside antibiotic used in veterinary medicine. It is produced by Streptomyces tenebrarius.

<span class="mw-page-title-main">Polymyxin B</span> Antibiotic medication

Polymyxin B, sold under the brand name Poly-Rx among others, is an antibiotic used to treat meningitis, pneumonia, sepsis, and urinary tract infections. While it is useful for many Gram negative infections, it is not useful for Gram positive infections. It can be given by injection into a vein, muscle, or cerebrospinal fluid or inhaled. The injectable form is generally only used if other options are not available. It is also available as the combinations bacitracin/polymyxin B and neomycin/polymyxin B/bacitracin for use on the skin.

<span class="mw-page-title-main">Cefotiam</span> Chemical compound

Cefotiam is a parenteral third-generation cephalosporin antibiotic. It has broad-spectrum activity against Gram-positive and Gram-negative bacteria. As a beta-lactam, its bactericidal activity results from the inhibition of cell wall synthesis via affinity for penicillin-binding proteins.

<span class="mw-page-title-main">Netilmicin</span> Chemical compound

Netilmicin (1-N-ethylsisomicin) is a semisynthetic aminoglycoside antibiotic, and a derivative of sisomicin, produced by Micromonospora inyoensis. Aminoglycoside antibiotics have the ability to kill a wide variety of bacteria. Netilmicin is not absorbed from the gut and is therefore only given by injection or infusion. It is only used in the treatment of serious infections particularly those resistant to gentamicin.

Tobramycin/dexamethasone, sold under the brand name Tobradex, is a fixed-dose combination medication in the form of eye drops and eye ointment, marketed by Alcon. The active ingredients are tobramycin and dexamethasone. It is prescribed for the treatment of pink eye in combination with bacterial infections.

<span class="mw-page-title-main">Sisomicin</span> Chemical compound

Sisomicin, is an aminoglycoside antibiotic, isolated from the fermentation broth of Micromonospora inositola. It is a newer broad-spectrum aminoglycoside most structurally related to gentamicin.

<span class="mw-page-title-main">Arbekacin</span> Antibiotic

Arbekacin (INN) is a semisynthetic aminoglycoside antibiotic which was derived from kanamycin. It is primarily used for the treatment of infections caused by multi-resistant bacteria including methicillin-resistant Staphylococcus aureus (MRSA). Arbekacin was originally synthesized from dibekacin in 1973 by Hamao Umezawa and collaborators. It has been registered and marketed in Japan since 1990 under the trade name Habekacin. Arbekacin is no longer covered by patent and generic versions of the drug are also available under such trade names as Decontasin and Blubatosine.

<span class="mw-page-title-main">Plazomicin</span> Antibiotic medication

Plazomicin, sold under the brand name Zemdri, is an aminoglycoside antibiotic used to treat complicated urinary tract infections. As of 2019 it is recommended only for those in whom alternatives are not an option. It is given by injection into a vein.

<span class="mw-page-title-main">Ceftolozane/tazobactam</span> Antibiotic

Ceftolozane/tazobactam, sold under the brand name Zerbaxa, is a combination antibiotic medication used for the treatment of complicated urinary tract infections and complicated intra-abdominal infections in adults. Ceftolozane is a cephalosporin antibiotic, developed for the treatment of infections with gram-negative bacteria that are resistant to conventional antibiotics. It was studied for urinary tract infections, intra-abdominal infections and ventilator-associated bacterial pneumonia.


  1. "Tobramycin Use During Pregnancy". 11 November 2019. Retrieved 28 April 2020.
  2. "Tobramycin ophthalmic Use During Pregnancy". 24 December 2019. Retrieved 28 April 2020.
  3. 1 2 "Tobramycin 40mg/ml Injection – Summary of Product Characteristics (SmPC)". (emc). 9 October 2018. Retrieved 28 April 2020.
  4. "FDA-sourced list of all drugs with black box warnings (Use Download Full Results and View Query links.)". FDA . Retrieved 22 October 2023.
  5. 1 2 3 4 5 6 7 Haberfeld H, ed. (2021). Austria-Codex (in German). Vienna: Österreichischer Apothekerverlag. Tobramycin B. Braun 1 mg/ml Infusionslösung.
  6. "Tobramycin" (PDF). Toku-E. 12 January 2010. Retrieved 11 June 2012.
  7. 1 2 Fischer J, Ganellin CR (2006). Analogue-based Drug Discovery. John Wiley & Sons. p. 507. ISBN   978-3-527-60749-5.
  8. 1 2 World Health Organization (2023). The selection and use of essential medicines 2023: web annex A: World Health Organization model list of essential medicines: 23rd list (2023). Geneva: World Health Organization. hdl: 10665/371090 . WHO/MHP/HPS/EML/2023.02.
  9. 1 2 "The Top 300 of 2021". ClinCalc. Archived from the original on 15 January 2024. Retrieved 14 January 2024.
  10. "Tobramycin - Drug Usage Statistics". ClinCalc. Retrieved 14 January 2024.
  11. "Tobi- tobramycin solution". DailyMed. 5 October 2018. Retrieved 28 April 2020.
  12. "Tobi Podhaler". European Medicines Agency (EMA). 17 September 2018. Retrieved 28 April 2020.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  13. "Tobrex- tobramycin ointment". DailyMed. 16 September 2019. Retrieved 28 April 2020.
  14. "Tobradex Eye Drops – Summary of Product Characteristics (SmPC)". (emc). 21 January 2020. Retrieved 28 April 2020.
  15. "Tobradex- tobramycin and dexamethasone ointment". DailyMed. 11 September 2019. Retrieved 28 April 2020.
  16. "Tobradex- tobramycin and dexamethasone suspension/ drops". DailyMed. 9 September 2019. Retrieved 28 April 2020.
  17. 1 2 "Tobramycin- tobramycin sulfate injection, powder, for solution". DailyMed. 11 October 2019. Retrieved 28 April 2020.
  18. "Tobramycin Susceptibility and Minimum Inhibitory Concentration (MIC) Data" (PDF). Toku-E.
  19. Haberfeld H, ed. (2021). Austria-Codex (in German). Vienna: Österreichischer Apothekerverlag. Tobrex Augentropfen.
  20. Lerner AM, Reyes MP, Cone LA, Blair DC, Jansen W, Wright GE, Lorber RR (May 1983). "Randomised, controlled trial of the comparative efficacy, auditory toxicity, and nephrotoxicity of tobramycin and netilmicin". Lancet. 1 (8334): 1123–6. doi:10.1016/S0140-6736(83)92864-7. PMID   6133153. S2CID   8303933.
  21. Neu HC (August 1976). "Tobramycin: an overview". The Journal of Infectious Diseases. 134 (Suppl): S3–19. doi:10.1093/infdis/134.supplement_1.s3. JSTOR   30106949. PMID   787451.
  22. Pedersen SS, Jensen T, Osterhammel D, Osterhammel P (April 1987). "Cumulative and acute toxicity of repeated high-dose tobramycin treatment in cystic fibrosis". Antimicrobial Agents and Chemotherapy. 31 (4): 594–9. doi:10.1128/AAC.31.4.594. PMC   174783 . PMID   3606063.
  23. Reyhanoglu G, Reddivari AK (January 2022). "Tobramycin". StatPearls. Treasure Island (FL): StatPearls Publishing. PMID   31869159.
  24. Yang G, Trylska J, Tor Y, McCammon JA (September 2006). "Binding of aminoglycosidic antibiotics to the oligonucleotide A-site model and 30S ribosomal subunit: Poisson-Boltzmann model, thermal denaturation, and fluorescence studies". Journal of Medicinal Chemistry. 49 (18): 5478–90. doi:10.1021/jm060288o. PMID   16942021.
  25. Haddad J, Kotra LP, Llano-Sotelo B, Kim C, Azucena EF, Liu M, et al. (April 2002). "Design of novel antibiotics that bind to the ribosomal acyltransfer site". Journal of the American Chemical Society. 124 (13): 3229–37. doi:10.1021/ja011695m. PMID   11916405.
  26. Kotra LP, Haddad J, Mobashery S (December 2000). "Aminoglycosides: perspectives on mechanisms of action and resistance and strategies to counter resistance". Antimicrobial Agents and Chemotherapy. 44 (12): 3249–56. doi:10.1128/aac.44.12.3249-3256.2000. PMC   90188 . PMID   11083623.
  27. Meylan S, Porter CB, Yang JH, Belenky P, Gutierrez A, Lobritz MA, et al. (February 2017). "Carbon Sources Tune Antibiotic Susceptibility in Pseudomonas aeruginosa via Tricarboxylic Acid Cycle Control". Cell Chemical Biology. 24 (2): 195–206. doi:10.1016/j.chembiol.2016.12.015. PMC   5426816 . PMID   28111098.

Further reading