Dexamethasone; neomycin; polymyxin B is indicated for the treatment of inflammatory ocular conditions where a risk of superficial bacterial infection exists. Together neomycin and polymyxin B displays activity against Enterobacter species, Escherichia coli, Haemophilus influenzae, Klebsiella species, Neisseria species, Pseudomonas aeruginosa, and Staphylococcus aureus. Clinicians may wish to consult the individual monographs for more information about each component.
Neomycin: Neomycin is bacteriocidal. It is actively transported into the bacterial cell where it binds to receptors present on the 30S ribosomal subunit of susceptible bacteria. This binding interferes with the initiation complex between the messenger RNA (mRNA) and the subunit. As a result, abnormal, nonfunctional proteins are formed due to misreading of the bacterial mRNA. Eventually, susceptible bacteria die because of the lack of functional proteins.
Polymyxin B: Polymyxin B binds to gram-negative bacterial cell membrane phospholipids. This binding destroys bacterial membranes with a surface detergent-like mechanism and increases the permeability of the cell membrane, which results in loss of metabolites essential to bacterial existence. Polymyxin B is bactericidal against most gram-negative bacilli. Polymyxin B has no in vitro activity against gram-positive organisms.
Dexamethasone: Dexamethasone is a corticosteroid with anti-inflammatory action. Corticosteroids are naturally occurring hormones that bind to specific protein receptors on targeted tissues. This binding induces a response by modifying transcription and, ultimately, protein synthesis to achieve the steroid's intended action. The anti-inflammatory action of dexamethasone results from the inhibition of leukocyte infiltration at the site of inflammation, interference in the function of mediators of inflammatory response, and suppression of humoral immune responses. The end result of treatment with dexamethasone includes reduction in edema or scar tissue as well as a general suppression of the immune response.
Lotemax is used in dry eye syndrome to decrease and eliminate inflammation of the ocular surface caused by the hyperosmolarity of the tears. The inflammation must first be brought under control before any other treatments can be optimally effective. Lotemax would typically be prescribed for two weeks to three months initially and then may need to be used again on a 1-2 week regimen periodically if the inflammation occurs again. Lotemax ointment has become a choice of many doctors to treat inflammation caused by dry eye (ocular surface disease) because it can be used at night with a long contact period to the eye's surfaces and provide some functional lubrication while the eyes are closed.