Polymyxin B-Trimethoprim Ophthalmic Solution Dosing for Bacterial Conjunctivitis
For bacterial conjunctivitis, instill one drop of polymyxin B-trimethoprim ophthalmic solution in the affected eye(s) every three hours (maximum of 6 doses per day) for 7 to 10 days. 1
Dosing Regimen Details
- Adult dosing: One drop every three hours (maximum 6 doses per day) for 7-10 days
- Pediatric dosing: Same as adults for children over 2 months of age 1
- Duration: Complete the full 7-10 day course even if symptoms improve earlier to prevent recurrence
Efficacy and Considerations
- Polymyxin B-trimethoprim is effective for treating bacterial conjunctivitis, with clinical studies showing 84% cure rates after completion of therapy 2
- Fourth-generation fluoroquinolones like moxifloxacin may provide faster resolution of symptoms (81% resolution at 48 hours vs. 44% with polymyxin B-trimethoprim) 3
- However, polymyxin B-trimethoprim remains a cost-effective first-line option with good efficacy against common conjunctivitis pathogens 4
Treatment Monitoring
Signs of Improvement
Monitor for these positive responses to therapy:
- Reduced discharge
- Decreased eyelid edema and conjunctival injection
- Reduced pain or discomfort
- Improved vision 5
When to Consider Alternative Treatment
- If no improvement within 48-72 hours
- If symptoms worsen despite appropriate therapy
- If vision deteriorates 4
Special Considerations
When to Refer to Ophthalmology
Immediate referral is necessary for patients with:
- Visual loss
- Moderate to severe pain
- Severe purulent discharge
- Corneal involvement
- Lack of response to therapy within 48-72 hours
- Recurrent episodes 4
Infection Control Measures
- Frequent handwashing
- Avoid sharing towels, washcloths, and pillows
- Avoid touching or rubbing eyes
- Change pillowcases frequently during infection 4
- Patients can typically return to work or school after 24 hours of antibiotic treatment 4
Potential Pitfalls
- Overuse of antibiotics for viral conjunctivitis (which doesn't respond to antibiotics)
- Inadequate duration of treatment leading to recurrence
- Failure to recognize potentially serious causes of conjunctivitis requiring specialized care
- Delayed referral for severe or non-responsive cases 4
Remember that bacterial conjunctivitis is typically self-limiting, but appropriate antibiotic therapy can speed recovery, reduce symptom duration, and minimize disease transmission.