What are the risks and considerations for chronic use of Polytrim (polymyxin B and trimethoprim)?

Risks of Chronic Polytrim (Polymyxin B and Trimethoprim) Use

Chronic use of Polytrim (polymyxin B and trimethoprim) ophthalmic solution should be avoided due to risks of hypersensitivity reactions, photosensitivity, and potential for antimicrobial resistance. 1

Adverse Effects of Long-Term Use

Common Adverse Reactions

• Local irritation (increased redness, burning, stinging, itching)
• Hypersensitivity reactions (lid edema, increased redness, tearing, circumocular rash)
• Photosensitivity (particularly associated with the trimethoprim component) 1

Systemic Concerns

• Trimethoprim may interfere with folic acid metabolism, which is particularly concerning for pregnant women 1
• Trimethoprim can increase the risk of hyperkalaemia, especially in patients with chronic kidney disease or those taking ACE inhibitors, ARBs, spironolactone, amiloride, or triamterene 2
• While rare with ophthalmic use, systemic absorption could potentially lead to blood dyscrasias with prolonged use 2

Antimicrobial Resistance Considerations

The Centers for Disease Control and Prevention (CDC) emphasizes antibiotic stewardship, which includes limiting antibiotic use to the shortest possible duration 2. Chronic use of Polytrim raises several concerns:

• Development of resistant bacterial strains
• Disruption of normal ocular surface microbiome
• Potential for more difficult-to-treat infections in the future

Special Population Considerations

Pregnancy

• Trimethoprim has been shown to be teratogenic in animal studies at high doses
• Should be used during pregnancy only if potential benefit justifies the potential risk 1

Nursing Mothers

• Unknown if excreted in human milk; caution advised 1

Pediatric Use

• Safety not established in children below 2 months of age 1

Monitoring Recommendations for Chronic Use

If chronic use is absolutely necessary despite the risks:

1. Regular ophthalmologic examinations to monitor for:

   • Development of hypersensitivity reactions
   • Changes in ocular surface health
   • Signs of secondary infections

2. Consider periodic breaks in therapy if possible

3. Educate patients about:

   • Sun protection due to photosensitivity risk
   • Signs of hypersensitivity reactions requiring immediate discontinuation
   • Proper administration technique to minimize systemic absorption

Alternative Approaches

For conditions requiring chronic antimicrobial therapy, consider:

1. Rotating different classes of antibiotics to reduce resistance development
2. Using preservative-free formulations when available
3. Exploring non-antibiotic alternatives when appropriate for the underlying condition

Conclusion

While Polytrim is effective for short-term treatment of bacterial conjunctivitis 3, 4, 5, 6, its chronic use carries significant risks including hypersensitivity reactions, photosensitivity, and antimicrobial resistance. The FDA labeling does not support long-term continuous use, and alternative management strategies should be considered for chronic ocular conditions.