Adult Dosing for Polymyxin B Sulfate/Trimethoprim Eye Drops for Bacterial Conjunctivitis
The recommended adult dose is one drop in the affected eye(s) every 3 hours (maximum 6 doses per day) for 7-10 days. 1
Standard Dosing Regimen
- Instill 1 drop every 3 hours while awake (approximately 6 times daily) in the affected eye(s) 1
- Treatment duration: 7-10 days for mild to moderate bacterial conjunctivitis 1
- This dosing schedule applies equally to adults and children over 2 months of age 1
Important Clinical Context
While polymyxin B/trimethoprim is FDA-approved and effective for bacterial conjunctivitis, newer fluoroquinolones (moxifloxacin, azithromycin, gatifloxacin) are now preferred as first-line agents due to superior efficacy and faster symptom resolution 2
Comparative Efficacy Considerations
- Moxifloxacin achieves significantly faster cure rates than polymyxin B/trimethoprim: 81% complete resolution at 48 hours versus 44% (P=0.001) 3
- Moxifloxacin requires only 3 times daily dosing versus 6 times daily for polymyxin B/trimethoprim, improving compliance 3
- Fluoroquinolones achieve better tissue penetration and broader coverage for bacterial conjunctivitis 2
When Polymyxin B/Trimethoprim Remains Appropriate
- Cost-effective alternative when fluoroquinolones are not accessible or affordable 2
- Effective for common pathogens: Haemophilus influenzae and Streptococcus pneumoniae with cure/improvement rates of 92-93% by end of therapy 4
- Well-tolerated with minimal adverse effects reported in pediatric and adult populations 5
Clinical Monitoring
- Expect improvement within 24-48 hours: reduced discharge, pain, and lid edema 2
- If no improvement by 48 hours, consider switching to a fluoroquinolone or obtaining cultures 2
- Complete the full 7-10 day course even if symptoms resolve earlier to prevent resistance 1
Important Contraindications
Do not use polymyxin B/trimethoprim for: