Polymyxin B/Trimethoprim Eye Drop Dosage 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 7-10 days. 1, 2
Dosage Protocol
- For mild to moderate bacterial conjunctivitis, the FDA-approved regimen is one drop in the affected eye(s) every three hours, not exceeding 6 doses daily, for a period of 7-10 days 1, 2
- This dosage is the same for adults and pediatric patients over two months of age 1
- A 5-7 day course is typically sufficient for mild cases, but the full 10-day course may be necessary for more persistent infections 3
Efficacy and Treatment Considerations
- Polymyxin B/Trimethoprim is effective for bacterial conjunctivitis, with clinical studies showing elimination of bacteria from the eyes with similar effectiveness to other topical antibiotics 4, 5
- Topical antibiotics are recommended for bacterial conjunctivitis as they reduce symptom duration and improve clinical outcomes, even in mild cases 3
- For moderate to severe bacterial conjunctivitis, obtain conjunctival cultures and Gram staining before initiating treatment 3
Special Considerations
- Polymyxin B/Trimethoprim alone is insufficient for gonococcal conjunctivitis, which requires systemic antibiotic therapy in addition to topical treatment 6, 3
- Similarly, chlamydial conjunctivitis requires systemic antibiotic therapy rather than topical treatment alone 6, 3
- Some studies suggest that fluoroquinolones like moxifloxacin may work faster than Polymyxin B/Trimethoprim, with one study showing 81% resolution at 48 hours with moxifloxacin versus 44% with Polymyxin B/Trimethoprim 7
Follow-up and Monitoring
- Patients should be advised to return for follow-up if no improvement is seen after 3-4 days of treatment 6, 3
- At follow-up visits, perform interval history, visual acuity measurement, and slit-lamp biomicroscopy 6
When to Refer to an Ophthalmologist
- Refer patients to an ophthalmologist if they experience visual loss, moderate or severe pain, severe purulent discharge, corneal involvement, conjunctival scarring, lack of response to therapy, or recurrent episodes 6, 3
- Hospitalization may be necessary for severe gonococcal conjunctivitis and is mandatory for neonatal conjunctivitis 6