Tobramycin is an aminoglycoside

Aminoglycoside

An aminoglycoside is a molecule or a portion of a molecule composed of amino-modifiedsugars.Several aminoglycosides function as antibiotics that are effective against certain types of bacteria...

 antibiotic

Antibiotic

An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

 used to treat various types of bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

l infections, particularly Gram-negative

Gram-negative

Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

 infections.

Mechanism of action

Tobramycin works by binding to a site on the bacterial 30S

30S

30S is the smaller subunit of the 70S ribosome of prokaryotes. It is a complex of ribosomal RNA and ribonucleoproteins that functions in mRNA translation...

 and 50S

50S

50S is the larger subunit of the 70S ribosome of prokaryotes. It is the site of inhibition for antibiotics such as macrolides, chloramphenicol, clindamycin, and the pleuromutilins. It includes the subunits 5S and 23S.-Structure:...

 ribosome

Ribosome

A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....

, preventing formation of the 70S complex. As a result, mRNA cannot be translated into protein and cell death ensues.
Tobramycin is preferred over gentamicin for Pseudomonas aeruginosa pneumonia due to better lung penetration and bactericidal activity.

Administration

Like all aminoglycosides, tobramycin does not pass the gastro-intestinal tract, so for systemic

Systemic

Systemic refers to something that is spread throughout, system-wide, affecting a group or system such as a body, economy, market or society as a whole. Systemic may also refer to:-In medicine:...

 use it can only be given intravenously

Intravenous therapy

Intravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...

, intramuscularly

Intramuscular injection

Intramuscular injection is the injection of a substance directly into a muscle. In medicine, it is one of several alternative methods for the administration of medications . It is used for particular forms of medication that are administered in small amounts...

, eyedrops (commonly with Dextramethsone), or it can be administered and inhaled via nebuliser. The formulation for injection is branded Nebcin. Patients with cystic fibrosis

Cystic fibrosis

Cystic fibrosis is a recessive genetic disease affecting most critically the lungs, and also the pancreas, liver, and intestine...

 will often take an inhalational

Inhaler

An inhaler or puffer is a medical device used for delivering medication into the body via the lungs. It is mainly used in the treatment of asthma and Chronic Obstructive Pulmonary Disease . Zanamivir , used to treat influenza, must be administered via inhaler...

 (nebulised) form (Tobi) for suppression of Pseudomonas aeruginosa

Pseudomonas aeruginosa

Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...

infections. Tobramycin is also combined with dexamethasone

Dexamethasone

Dexamethasone is a potent synthetic member of the glucocorticoid class of steroid drugs. It acts as an anti-inflammatory and immunosuppressant...

 as an ophthalmic solution

Tobradex

Tobramycin/dexamethasone is a prescription medication in the form of eye drops and eye ointment, marketed by Alcon. The active ingredients are tobramycin 0.3% and dexamethasone 0.1% . It is prescribed for a wide spectrum of bacterial eye infections...

 (TobraDex

Tobradex

Tobramycin/dexamethasone is a prescription medication in the form of eye drops and eye ointment, marketed by Alcon. The active ingredients are tobramycin 0.3% and dexamethasone 0.1% . It is prescribed for a wide spectrum of bacterial eye infections...

).

Bausch & Lomb Pharmaceuticals

Bausch & Lomb

Bausch & Lomb, an American company based in Rochester, New York, is one of the world's leading suppliers of eye health products, such as contact lenses and lens care products today. In addition to this main activity, in recent years the area of medical technology has been developed...

 produces a sterile tobramycin solution (eye-drops) with a tobramycin concentration of 0.3%, which is available by prescription only in the United States and Canada. (In some countries, such as Italy, it is available over the counter.) It is mixed with 0.01% benzalkonium chloride

Benzalkonium chloride

Benzalkonium chloride, also known as alkyldimethylbenzylammonium chloride and ADBAC, is a mixture of alkylbenzyldimethylammonium chlorides of various even-numbered alkyl chain lengths. This product is a nitrogenous cationic surface-acting agent belonging to the quaternary ammonium group...

 as a preservative. These concentrations result in 3 mg per ml and 0.1 mg per ml, respectively.

A proprietary formulation of micronized, nebulized tobramycin has been tested as a treatment for bacterial sinusitis

Sinusitis

Sinusitis is inflammation of the paranasal sinuses, which may be due to infection, allergy, or autoimmune issues. Most cases are due to a viral infection and resolve over the course of 10 days...

.

Side effects

Like other aminoglycosides, tobramycin can cause deafness or a loss of equilibrioception

Equilibrioception

Equilibrioception or sense of balance is one of the physiological senses. It helps prevent humans and animals from falling over when walking or standing still. Balance is the result of a number of body systems working together: the eyes , ears and the body's sense of where it is in space ideally...

 (vertigo) in genetically susceptible individuals. These individuals have a normally harmless mutation in their DNA, that allows the tobramycin to affect their cells. The cells of the ear

Ear

The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....

 are particularly sensitive to this.

Tobramycin can also be highly toxic to the kidney

Kidney

The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

s, particularly if multiple doses accumulate over a course of treatment.

For these reasons, when tobramycin is given parenteral

Parenteral

Parenteral is a route of administration that involves piercing the skin or mucous membrane. Parenteral nutrition refers to providing nutrition via the veins.-Etymology:...

ly, it is usually dosed by body weight

Body weight

The term body weight is used in daily English speech as well as in the contexts of biological and medical sciences to describe the mass of an organism's body. Body weight is measured in kilograms throughout the world, although in some countries it is still measured in pounds or stones and pounds...

. Various formulae exist for calculating tobramycin dosage. Also serum levels of tobramycin are monitored during treatment.