Polymyxin B Sulfate and Trimethoprim is a combination antibiotic medication primarily used as an ophthalmic (eye) solution. It works to combat bacterial infections affecting the eyes by targeting and eliminating various bacteria responsible for ocular infections. This medication is available by prescription only.
Conditions Treated
This medication treats bacterial eye infections, including bacterial conjunctivitis (pink eye), blepharitis, and other superficial ocular infections. It is effective against a broad spectrum of bacteria, such as Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Haemophilus influenzae, and Pseudomonas aeruginosa.
How It Works
Polymyxin B Sulfate and Trimethoprim work together through distinct mechanisms to eliminate bacterial infections. Polymyxin B Sulfate, a polypeptide antibiotic, targets the bacterial cell membrane, disrupting its structure and causing cell death. This action is particularly effective against Gram-negative bacteria. Trimethoprim inhibits bacterial folate synthesis by blocking the enzyme dihydrofolate reductase, which prevents bacteria from producing essential components for DNA and protein synthesis, stopping their multiplication. The combined action of these two antibiotics provides a broader spectrum of activity and helps reduce the likelihood of bacteria developing resistance.
Proper Usage
Administering Polymyxin B Sulfate and Trimethoprim eye drops requires careful attention to ensure effectiveness and prevent contamination. Always wash your hands thoroughly with soap and water before and after applying the drops.
To apply, tilt your head back, gently pull down your lower eyelid to form a small pouch, and instill the prescribed number of drops into this pocket. Avoid touching the dropper tip to your eye, fingers, or any other surface to maintain sterility. After instilling the drop, close your eye gently and press a finger to the inside corner of your eye near the nose for 1 to 2 minutes. This technique helps prevent the medication from draining out and ensures it stays in contact with the eye.
The typical dosage is one drop in the affected eye(s) every three hours, up to a maximum of six doses per day, for a period of 7 to 10 days. It is important to complete the full course of treatment, even if symptoms improve, to ensure the infection is fully cleared and to minimize the risk of bacterial resistance. Store the medication at room temperature (15°C to 25°C) and protect it from light.
Key Safety Information
When using Polymyxin B Sulfate and Trimethoprim, certain safety considerations are important. Common side effects may include temporary eye irritation, such as redness, burning, stinging, or itching, immediately after instillation. Some individuals might also experience increased tearing or temporary blurred vision. These effects are generally mild and do not require medical attention unless they persist or worsen.
More serious, though less common, side effects can include allergic reactions, such as a skin rash, hives, or swelling of the face, lips, tongue, or throat. If an allergic reaction occurs, discontinue use and seek immediate medical attention.
Patients should avoid wearing contact lenses during treatment for bacterial eye infections, as contact lenses can interfere with healing or become contaminated. If symptoms do not improve within a few days, or if they worsen, it is advisable to consult a healthcare professional. This medication is not for injection into the eye. Prolonged use of any antibiotic, including this combination, may lead to the overgrowth of other organisms, such as fungi. Individuals who are pregnant or breastfeeding should discuss the use of this medication with their doctor.