Neomycin Sulfate/Polymyxin B Sulfate/Dexamethasone

**Semantic type:** Amino Acid, Peptide, or Protein|Pharmacologic Substance

**Definition:** A topical combination preparation containing the sulfate salt form of the aminoglycoside antibiotic neomycin, the sulfate salt form of the polypeptide antibiotic polymyxin B, and the glucocorticoid dexamethasone, with antimicrobial, anti-infective and anti-inflammatory activities. Upon topical application, neomycin irreversibly binds to the bacterial 30S ribosomal subunit, thereby preventing mRNA from binding, causing both misreading and the inhibition of protein synthesis. Polymyxin B binds, with its positively charged amino groups, to negatively charged phospholipids in the outer cell membrane of Gram-negative bacteria, thereby disrupting cell wall integrity and altering the permeability of the bacterial cytoplasmic membrane. Dexamethasone binds to the cytoplasmic glucocorticoid receptor, and this receptor-ligand complex is translocated to the nucleus where it initiates the transcription of genes encoding for anti-inflammatory mediators, such as cytokines and lipocortins.

**Synonyms:** - Maxitrol - Maxitrol Eye Drops