What is Maxitrol (dexamethasone and neomycin)?

Maxitrol: A Combination Ophthalmic Medication

Maxitrol is an ophthalmic suspension containing neomycin sulfate, polymyxin B sulfate, and dexamethasone, used primarily to treat ocular infections with inflammation.

Composition and Formulation

• Maxitrol contains three active ingredients: neomycin sulfate (equivalent to 3.5 mg neomycin base), polymyxin B sulfate (equivalent to 10,000 polymyxin B units), and dexamethasone 10 mg (1%) 1
• The formulation includes preservatives (thimerosal 0.001%) and inactive ingredients such as cetyl alcohol, glyceryl monostearate, mineral oil, polyoxyl 40 stearate, propylene glycol, and water for injection 1

Mechanism of Action

• Antimicrobial components: Neomycin and polymyxin B provide coverage against specific susceptible organisms 1

  • Effective against: Staphylococcus aureus, Escherichia coli, Haemophilus influenzae, Klebsiella/Enterobacter species, Neisseria species, and Pseudomonas aeruginosa 1
  • Not effective against: Serratia marcescens and streptococci, including Streptococcus pneumoniae 1

• Anti-inflammatory component: Dexamethasone (corticosteroid) suppresses inflammatory response 1

  • Inhibits inflammatory mediators
  • May delay healing and potentially inhibit the body's defense mechanism against infection 1

Clinical Applications

• Treatment of bacterial ocular infections with associated inflammation 2
• Management of bacterial blepharitis and conjunctivitis 2
• Post-operative control of inflammation following cataract surgery 3
• Treatment of external ocular inflammatory conditions where bacterial infection or risk of infection exists 2, 3

Efficacy

• In treating bacterial blepharitis and conjunctivitis, Maxitrol demonstrated:

  • 90% reduction in bacterial counts
  • 50% bacterial eradication rate (significantly higher than dexamethasone alone at 17%) 2
  • Greater reduction in conjunctival discharge compared to steroid-only treatment 2

• For post-cataract surgery inflammation:

  • Similar anti-inflammatory efficacy to other steroid-antibiotic combinations 3
  • Effective control of intraocular inflammation 3

Potential Side Effects and Concerns

• Allergic reactions: Neomycin is the most common substance causing contact sensitivity in topical ophthalmic preparations (5-15% of patients with chronic external otitis) 4
• Hypersensitivity: Patch testing has demonstrated that approximately 13% of normal volunteers are hypersensitive to neomycin 4
• Potential toxicity: Long-term use of neomycin has been associated with ototoxicity, nephrotoxicity, and neurotoxicity concerns 4
• Superinfection: Corticosteroid component may inhibit immune response, potentially allowing opportunistic infections, particularly fungal infections 1

Cautions and Considerations

• Should be used with caution in patients with history of hypersensitivity to any of the components 4
• Prolonged use may lead to overgrowth of non-susceptible organisms, including fungi 1
• In patients with thin corneas or underlying ocular surface disease (e.g., Sjögren's syndrome), careful monitoring is required as cases of corneal perforation have been reported 5
• Not recommended for long-term use due to potential neomycin toxicity concerns 2

Comparison to Other Ophthalmic Combinations

• In post-cataract surgery studies, Maxitrol (dexamethasone-neomycin-polymyxin) showed:
  • Similar anti-inflammatory efficacy to tobramycin-dexamethasone 3
  • Less effective reduction of ocular bacterial flora compared to fluorometholone-gentamicin combination 6

Clinical Pearls

• The fixed-dose combination provides better compliance advantage compared to administering separate antimicrobial and anti-inflammatory agents 1
• Maxitrol should not be used for extended periods due to potential for developing antibiotic resistance and hypersensitivity reactions 4, 2
• Always consider potential allergic reactions, particularly in patients with chronic ocular surface inflammation or previous exposure to topical antibiotics 4