Polymyxin B sul-trimethoprim is an antibiotic eye drop that combats bacterial infections affecting the eye. This medication combines two distinct antibiotic agents, polymyxin B and trimethoprim, to treat eye conditions caused by bacteria. Its purpose is to eliminate or inhibit bacterial growth, alleviating symptoms and promoting healing.
How It Fights Eye Infections
Polymyxin B and trimethoprim work together to disrupt bacterial processes, leading to the eradication of the infection. Polymyxin B, a polypeptide antibiotic, primarily targets the outer cell membrane of Gram-negative bacteria. It binds to lipopolysaccharides and phospholipids within the bacterial membrane, destabilizing its structure and increasing permeability. This disruption causes the leakage of intracellular contents, leading to bacterial cell death.
Trimethoprim interferes with bacterial metabolism by inhibiting dihydrofolate reductase (DHFR). This enzyme is crucial for synthesizing tetrahydrofolic acid (THF), a form of folic acid necessary for bacteria to produce nucleic acids and proteins. By blocking this step, trimethoprim prevents bacteria from replicating and growing.
The combination of these two antibiotics offers a synergistic effect. Polymyxin B targets the cell membrane, while trimethoprim interferes with internal metabolic pathways. This dual mechanism broadens the spectrum of bacteria the medication can effectively treat and may help reduce antibiotic resistance.
What It Treats and How to Apply It
This antibiotic eye drop is commonly prescribed for various bacterial eye infections. It treats bacterial conjunctivitis, often known as “pink eye,” and blepharoconjunctivitis, an inflammation affecting both the conjunctiva and the eyelids. This medication is effective only against bacterial infections and will not treat infections caused by viruses or fungi.
Proper application of the eye drops prevents contamination. Wash your hands thoroughly with soap and water. Tilt your head back slightly or lie down, then gently pull down your lower eyelid to create a small pocket.
Hold the dropper tip above your eye, being careful not to touch the tip to your eye, eyelid, or any other surface. Squeeze the bottle gently to release one drop into the pocket. Close your eye gently for one to two minutes, without blinking or squeezing. Apply gentle pressure to the inner corner of your eye near your nose for about one minute to prevent the medication from draining into your tear duct. If using other eye drops, wait at least 5 to 10 minutes between different medications.
Typical dosage for adults and children two months of age and older is one drop in the affected eye(s) every three hours, for 7 to 10 days. This amounts to a maximum of six doses per day. Your doctor may adjust the frequency for more severe infections, so always follow specific prescription instructions.
Important Safety Information
Polymyxin B sul-trimethoprim eye drops can cause some side effects. Common, mild reactions include temporary stinging, burning, itching, or increased redness of the eye. If these symptoms are severe or do not subside, or if you experience eyelid swelling or a rash, contact your doctor immediately.
Do not use this product if you have a known allergy to polymyxin B or trimethoprim. If you wear contact lenses, remove them before applying the eye drops, as the preservative can discolor soft lenses. Wait at least 15 minutes after application before reinserting contact lenses.
To prevent contamination, avoid touching the dropper tip to any surface, including your eye or fingers. Do not share your eye drops, and discard the bottle after completing the prescribed treatment course or if it has expired. Inform your doctor about all other medications you are taking, including other eye drops, to avoid potential interactions.
If you are pregnant or breastfeeding, consult your doctor before using this medication. Completing the full course of treatment is important, even if symptoms improve. Stopping early can allow remaining bacteria to multiply, potentially leading to a return of the infection and contributing to antibiotic resistance.