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Pharmaco-therapeutic group: Dexa-Gentamicin is active against inflammations or hypersensitivities to certain substances (allergies) of the eye. ATC-Code: S01CA01.
Pharmacology: Eye oint: Dexa-Gentamicin is a combination of gentamicin sulfate, as antibiotic drug with a broad spectrum activity against gram negative and gram positive germs and dexamethasone, an anti-inflammatory and antiallergic active drug.
Topically applied gentamicin is absorbed by conjunctiva and cornea and is detectable in the aqueous humor 15 minutes after application.
Using gentamicin on intact mucous membrane of the eye, no detectable amounts of gentamicin are to be expected in serum. Dexamethasone poorly penetrate an intact corneal epithelium. The penetration is significantly elevated in eyes with inflammed or lesioned mucosal membranes.
Gentamicin is active against a wide variety of pathogenic gram-negative and gram-positive bacteria. The gram-negative bacteria which are sensitive to gentamicin include certain strains of Pseudomonas aeruginosa, Staphylococcus aureus, indole-positive and indole-negative Proteus species, Escherichia coli, Haemophilus influenzae and Haemophilus aegyptius and Neisseria species, including Neisseria gonorrhoeae.
The gram-positive bacteria against which gentamicin is active induce coagulase-positive and coagulase-negative staphylococci, inclusive of certain strains that are resistant to penicillin, group-A beta-hemolytic and nonhemolytic streptococci and Diplococcus pneumoniae.
Pharmacodynamics: Eye drops: Antibiotic: The bactericidal action of Gentamicin is based on an irreversible inhibition of the bacterial protein synthesis.
Gentamicin elicits rapid bacterial action by acting directly on the bacterial ribosome, where it disrupts the normal cycle of ribosomal function. Additionally, Gentamicin includes misreading of the genetic code of the mRNA template, leading to incorporation of incorrect amino acids into the growing polypeptide chain.
Corticosteroid: The corticosteroid's method of action is not yet completely known. The corticosteroids are thought to act by controlling the rate of synthesis of proteins important for chemotactic and immunologic reactions.
Modifications of the leukocyte's and macrophage's functions seem to have an influence on the suppression of inflammatory and allergic reactions.
Pharmacokinetics: Eye drops: Antibiotic: Systemically available Gentamicin has a half-life of plasma elimination of 2 to 3 hours in healthy adults and is excreted unchanged by the kidneys. Topically applied, Gentamicin is absorbed by conjunctiva and cornea and is detectable in the aqueous humour 15 minutes after application. Using Gentamicin on intact mucous membranes of the eye, no detectable amounts of Gentamicin are to be expected in serum.
Corticosteroid: Dexamethasone sodium phosphate and Dexamethasone poorly penetrate an intact corneal epithelium. The penetration is significantly elevated in eyes with inflammed or lesioned mucosal membranes.
Systemically absorbed Dexamethasone is bound to proteins to 80%. It is excreted by the kidneys (as glucuronide) with a half-life of 3 to 4 hours.
