trimethoprim + polymyxin B

**Trimethoprim + polymyxin B** is a fixed-dose topical ophthalmic antibacterial combination marketed as Polytrim. It contains trimethoprim, a selective reversible inhibitor of bacterial dihydrofolate reductase that blocks tetrahydrofolate synthesis and thereby impairs bacterial nucleic-acid and protein synthesis, plus polymyxin B, a cyclic lipopeptide antibiotic that disrupts bacterial cell-membrane permeability. The sterile ophthalmic solution contains trimethoprim 1 mg/mL and polymyxin B 10,000 units/mL and is approved for susceptible bacterial surface eye infections, including acute bacterial conjunctivitis and blepharoconjunctivitis. ([accessdata.fda.gov](https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/050567s028lbl.pdf))

Brand names

PolytrimSandoz Polytrimethoprim

Other names

polymyxin B + trimethoprimpolymyxin B sulfate + trimethoprim sulfatepolymyxin B/trimethoprimtrimethoprim + polymyxin Btrimethoprim sulfate + polymyxin B sulfatetrimethoprim/polymyxin B