Polymyxin B Sulfate And Trimethoprim Sulfate

Polymyxin B Sulfate and Trimethoprim Ophthalmic Solution, USP is indicated in the treatment of surface ocular bacterial infections, including acute bacterial conjunctivitis, and blepharoconjunctivitis, caused by susceptible strains of the following microorganisms:

^*Efficacy for this organism in this organ system was studied in fewer than 10 infections.

In mild to moderate infections, instill one drop in the affected eye(s) every three hours (maximum of 6 doses per day) for a period of 7 to 10 days.

The most frequent adverse reaction to polymyxin B sulfate and trimethoprim ophthalmic solution is local irritation consisting of increased redness, burning, stinging, and/or itching. This may occur on instillation, within 48 hours, or at any time with extended use. There are also multiple reports of hypersensitivity reactions consisting of lid edema, itching, increased redness, tearing, and/or circumocular rash. Photosensitivity has been reported in patients taking oral trimethoprim.

Polymyxin B Sulfate and Trimethoprim Ophthalmic Solution, USP is a sterile antimicrobial solution for topical ophthalmic use. It has pH of 4.0 to 6.2 and osmolality of 270 to 310 mOsm/kg.

Trimethoprim, 5-(3,4,5-Trimethoxybenzyl)pyrimidine-2,4-,diamine, is a white, odorless, crystalline powder with a molecular weight of 290.3 and the following structural formula:

Polymyxin B sulfate is the sulfate salt of polymyxin B₁ and B₂ which are produced by the growth of

Trimethoprim is a synthetic antibacterial drug active against a wide variety of aerobic gram-positive and gram-negative ophthalmic pathogens. Trimethoprim blocks the production of tetrahydrofolic acid from dihydrofolic acid by binding to and reversibly inhibiting the enzyme dihydrofolate reductase. This binding is stronger for the bacterial enzyme than for the corresponding mammalian enzyme and therefore selectively interferes with bacterial biosynthesis of nucleic acids and proteins.

Polymyxin B, a cyclic lipopeptide antibiotic, is bactericidal for a variety of gram-negative organisms, especially Pseudomonas aeruginosa. It increases the permeability of the bacterial cell membrane by interacting with the phospholipid components of the membrane.

Blood samples were obtained from 11 human volunteers at 20 minutes, 1 hour and 3 hours following instillation in the eye of 2 drops of ophthalmic solution containing 1 mg trimethoprim and 10,000 units polymyxin B per mL. Peak serum concentrations were approximately 0.03 mcg/mL trimethoprim and 1 unit/mL polymyxin B.