Polytrim (Polymyxin B / Trimethoprim)

Approved uses

Acute bacterial conjunctivitis

1 drop in the affected eye(s) every 3 hours, maximum 6 doses per day, for 7 to 10 days in mild to moderate infection

Clinical cure in 96% of children by day 7 to 10, matching moxifloxacin.

Bacterial blepharoconjunctivitis

1 drop in the affected eye(s) every 3 hours, maximum 6 doses per day, for 7 to 10 days in mild to moderate infection

Dose: FDA label, Dosage and Administration. Lamberts DW, Buka T, Knowlton GM. Clinical evaluation of trimethoprim-containing ophthalmic solutions in humans. Am J Ophthalmol. 1984;98(1):11-16 (randomized controlled trial, double-masked).

Contraindications

Known hypersensitivity to any component of the product.

Available Forms

Ophthalmic solution, 10 mL opaque white LDPE dispenser bottle, polymyxin B sulfate 10,000 units/mL, trimethoprim sulfate equivalent to 1 mg/mL, benzalkonium chloride 0.04 mg/mL preservative

Mechanism of Action

Trimethoprim binds and reversibly inhibits bacterial dihydrofolate reductase, blocking production of tetrahydrofolic acid from dihydrofolic acid, and because that binding is stronger for the bacterial than the mammalian enzyme it selectively interferes with bacterial nucleic acid and protein synthesis across gram-positive and gram-negative ophthalmic pathogens. Polymyxin B, a cyclic lipopeptide, is bactericidal for a variety of gram-negative organisms, especially Pseudomonas aeruginosa, and increases bacterial cell membrane permeability by interacting with the membrane phospholipids.