Polymyxin B Eye Drops: Indications and Usage
Polymyxin B eye drops should be used for bacterial conjunctivitis and as prophylaxis for bacterial keratitis following corneal abrasion or trauma, particularly when treatment is started within 24 hours of the injury. 1
Primary Indications
- Polymyxin B eye drops (typically combined with trimethoprim) are indicated for the treatment of bacterial conjunctivitis 2, 3
- They serve as prophylactic treatment following corneal abrasion to prevent bacterial keratitis, especially when started within 24 hours of injury 1
- Polymyxin B combinations are effective against both gram-positive and gram-negative pathogens commonly causing ocular surface infections 2
Specific Clinical Scenarios
Bacterial Conjunctivitis
- Polymyxin B (typically combined with trimethoprim) is effective for bacterial conjunctivitis with clinical cure rates of 83-95% 4, 3
- The standard dosing regimen is one drop in the affected eye(s) every three hours (maximum of 6 doses per day) for 7-10 days 5
- Pediatric patients over two months of age can receive the same dosing regimen as adults 5
Corneal Abrasions
- Prophylactic topical antibiotics including polymyxin B combinations are recommended following corneal abrasion to prevent ulceration 1
- For contact lens wearers with corneal abrasions, broad-spectrum antibiotics like polymyxin B combinations are particularly important due to higher infection risk 1, 6
Limitations and Considerations
- Polymyxin B eye ointments have limited corneal penetration compared to drops, making them more suitable for adjunctive therapy or bedtime use in less severe cases 1
- For central or severe keratitis, fluoroquinolones are generally preferred over polymyxin B combinations due to better tissue penetration 1
- Chronic use of prophylactic antibiotics including polymyxin B may promote growth of resistant organisms 1
- Hypersensitivity reactions to polymyxin B can range from local effects to generalized reactions including erythema, itching, urticaria, skin rash, and anaphylaxis 7
Comparative Efficacy
- Newer fluoroquinolones like moxifloxacin may work faster than polymyxin B combinations, with one study showing 81% resolution at 48 hours with moxifloxacin versus 44% with polymyxin B/trimethoprim 8
- However, trimethoprim-polymyxin B has been shown to be significantly better than chloramphenicol in reducing signs and symptoms of bacterial conjunctivitis 9
- For bacterial keratitis, single-drug therapy using a fluoroquinolone has been shown to be as effective as combination therapy utilizing fortified antibiotics 1
Special Populations
- Polymyxin B combinations have been shown to be safe and effective in pediatric patients over two months of age 5
- When combined with steroids (as in some formulations), caution is needed in patients with a history of herpes simplex, as steroids may exacerbate viral eye infections 7
Monitoring and Follow-up
- Regular follow-up is necessary to monitor healing and detect early signs of infection 6
- If using a polymyxin B formulation containing steroids, intraocular pressure should be routinely monitored if used for 10 days or longer 7
- Cross-hypersensitivity to other aminoglycosides can occur, and treatment should be discontinued if hypersensitivity develops 7