Known under its generic name as tombracyne, Tobrex is a sterile topical ophthalmic antibiotic formulation used primarily for therapy of external ophthalmic infections.
Tobrex - The Antibacterial Action
The agent is a water-soluble amino glycoside agent active against a wide variety of gram-positive and gram-negative ophthalmic pathogens. Tobrex is indicated in the treatment of external eye infections and its adnexa caused by susceptible bacteria.
The mechanism of its action is quite simple - Tobrex works by binding to a site on the bacterial 30S and 50S ribosome, causing the genetic code to be misread, which leads to a defective bacterial cell membrane during replication.
The systematic use of Tobrex is to be given intramuscularly or intravenously, because like all amino glycosides, tombramycin does not pass into the gastro-intestinal tract.
Tobrex has been demonstrated to be active against susceptible strains of some microorganisms like:
- any penicillin resistant-strains
- Staphylococci, including S. aureus and S. epidermidis
- some Streptococcus pneumonia
- most Proteus vulgaris strains
- Pseudomonas aeruginosa
- the Group A-beta-hemolytic species of Streptococci
- Acinetobacter calcoaceticus
- Escherichia coli, Klebsiella pneumoniae
- Morganella morganii, etc.
There are some individuals who have a normally harmless mutation in the DNA which may allow Trobex to affect their cells -- especially the cells of of the ear which are more sensitive. In these situations tombrocyne can cause vertigo or deafness. The drug may also be extremely toxic to the kidneys. Other adverse reactions to Tobrex include conjunctivae erythematic, lid itching and swelling, ocular toxicity, and hypersensitivity.
The recommended dosage for Tobrex is if the infection is mild to moderate is one or two drops of the solution into the affected eye(s) every four hours. If the infection is severe, two drops every four hours until improvements are noticed. Tobrex can be used with other medicines for eyes infections.
Tobrex has not been shown to cause any birth defects or other problems (although studies have not been done in humans) and also trobramycin is not likely to pass into the breast milk so it does not cause serious problems to nursing babies. The drug has been tested in children as well and is proven to be safe and effective for them.
Patients should inform their doctor if they ever had any allergic reaction to ophthalmic tobramycin or to any related medicines such as:
- netilmicin, neomycin
- amikacin, gentamicin
- kanamycin, streptomycin or trobamycin by injection.
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