What is polymyxin b/trimethoprim-ophthalmic, and how does it work (mechanism of action)?

Polymyxin B sulfate/trimethoprim is an antibiotic eye drop composed of two drugs. Polymyxin B sulfate works by altering bacterial cell wall structure that causes the leaking out of cellular contents that can result in cell death. Trimethoprim is an antibiotic that interferes with the production of tetrahydrofolic acid, a chemical that is necessary for bacteria and human cells to produce proteins. Trimethoprim inhibits production of tetrahydrofolic acid by inhibiting the enzyme responsible for making tetrahydrofolic acid from dihydrofolic acid. This inhibition interferes with the ability of bacteria to survive. Polymyxin B sulfate/trimethoprim is effective against gram-positive and gram-negative bacteria such as:

The FDA approved polymyxin B sulphate/trimethoprim in October 1988.

What brand names are available for polymyxin b/trimethoprim-ophthalmic?


Is polymyxin b/trimethoprim-ophthalmic available as a generic drug?


Do I need a prescription for polymyxin b/trimethoprim-ophthalmic?


What are the side effects of polymyxin b/trimethoprim-ophthalmic?

Side effects of polymyxin B sulfate/trimethoprim are

  • redness,
  • itching, and
  • irritation.
  • Hypersensitivity reactions like¬† edema (swelling) and rash may occur.

What is the dosage for polymyxin b/trimethoprim-ophthalmic?

The recommended dosing for polymyxin B sulfate/trimethoprim is to apply 1 drop into the affected eye(s) every 3 hours for 7 to 10 days with a maximum of 6 doses per day.

Which drugs or supplements interact with polymyxin b/trimethoprim-ophthalmic?

: Drug interactions have not been established for polymyxin B sulfate/trimethoprim combination eye drops.


Pink Eye (Conjunctivitis) Symptoms, Causes, Treatments See Slideshow

Is polymyxin b/trimethoprim-ophthalmic safe to take if I'm pregnant or breastfeeding?

: There are no adequate studies done on polymyxin B sulfate/trimethoprim to determine safe and effective use in pregnant women.

It is not known whether polymyxin B sulfate/trimethoprim enters breast milk. It is best use caution before using it in nursing mothers.

What else should I know about polymyxin b/trimethoprim-ophthalmic?

What preparations of polymyxin b/trimethoprim-ophthalmic are available?

Polymyxin B sulfate/trimethoprim is a sterile eye drop, containing polymyxin B sulfate 10,000 units/ml and trimethoprim sulfate 1 mg/ml, available in 10 ml dispenser bottles.

How should I keep polymyxin b/trimethoprim-ophthalmic stored?

Store polymyxin B sulfate/trimethoprim between temperatures of 15 C to 25 C (59 F - 77 F).


Polymyxin B sulfate and trimethoprim (Polytrim) is an antibacterial eye drop prescribed to treat bacterial conjunctivitis and blepharoconjunctivitis of the eyes. Side effects, drug interactions, pregnancy safety, dosage, and storage information should be reviewed prior to using this medication.

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