What is Polymyxin B and Trimethoprim Ophthalmic: Uses, Dosage, Side Effects and More

Polymyxin B and trimethoprim ophthalmic is a prescription antibiotic eye drop that combines two powerful medicines to fight bacterial eye infections. This combination works by attacking bacteria in two different ways, making it harder for the infection to survive and spread in your eye.

If you've been prescribed this medication, you're likely dealing with a bacterial eye infection that needs targeted treatment. The good news is that this combination has been helping people clear up stubborn eye infections for many years, and most people tolerate it well.

What is Polymyxin B and Trimethoprim Ophthalmic?

This medication is a combination of two antibiotics specifically designed for eye infections. Polymyxin B works by breaking down the outer wall of bacteria, while trimethoprim stops bacteria from making essential proteins they need to survive.

Think of it as a one-two punch against bacterial infections in your eyes. By combining these two medicines, doctors can target a broader range of bacteria that might be causing your eye infection. This makes the treatment more effective than using just one antibiotic alone.

The medication comes as eye drops that you apply directly to the affected eye. It's only available with a prescription because your doctor needs to confirm you have a bacterial infection before starting treatment.

What is Polymyxin B and Trimethoprim Ophthalmic Used For?

This combination treats bacterial infections of the eye and the area around your eye. Your doctor will prescribe it when they've determined that bacteria are causing your eye problems, not viruses or other causes.

The medication is commonly used for several types of bacterial eye infections. Here are the main conditions it helps treat:

• Bacterial conjunctivitis (pink eye caused by bacteria)
• Blepharitis (infection of the eyelid margins)
• Keratitis (infection of the cornea)
• Infections following eye surgery or injury
• Stye or chalazion with bacterial infection

Your doctor will examine your eye and may take a sample to identify the specific bacteria before prescribing this medication. This ensures you're getting the right treatment for your particular infection.

How Does Polymyxin B and Trimethoprim Ophthalmic Work?

This combination medication works by attacking bacteria through two different mechanisms, making it a moderately strong antibiotic treatment. Polymyxin B acts like a detergent, breaking apart the protective outer membrane of bacteria, while trimethoprim blocks the bacteria's ability to make DNA and reproduce.

When bacteria can't maintain their protective barrier and can't reproduce, they die off quickly. This dual approach is particularly effective against gram-positive bacteria like Staphylococcus and some gram-negative bacteria that commonly cause eye infections.

The medication starts working within hours of your first dose, though you might not notice improvement for 24 to 48 hours. Most people begin to feel relief from symptoms like redness, discharge, and irritation within the first few days of treatment.

How Should I Take Polymyxin B and Trimethoprim Ophthalmic?

You should use this medication exactly as your doctor prescribed, typically one drop in the affected eye every 3 to 4 hours while you're awake. The exact dosing schedule depends on the severity of your infection and your doctor's assessment.

Before applying the drops, wash your hands thoroughly with soap and water. Tilt your head back slightly and pull down your lower eyelid to create a small pocket. Hold the dropper above your eye without touching it to your eye or eyelid, then squeeze one drop into the pocket.

After applying the drop, close your eye gently and press lightly on the inner corner of your eye for about one minute. This helps prevent the medication from draining out too quickly and reduces the chance of it being absorbed into your bloodstream.

You don't need to take this medication with food since it goes directly into your eye. However, try to space your doses evenly throughout the day for the best results.

How Long Should I Take Polymyxin B and Trimethoprim Ophthalmic For?

Most people need to use this medication for 7 to 10 days, though your doctor might adjust this based on how quickly your infection responds. It's crucial to complete the full course even if your symptoms improve after just a few days.

Stopping the medication too early can allow surviving bacteria to multiply again, potentially leading to a stronger, more resistant infection. Your eye might look and feel better before all the bacteria are completely eliminated.

If your symptoms haven't improved after 3 to 4 days of treatment, contact your doctor. They may need to reassess your condition or consider whether a different antibiotic might work better for your specific infection.

What Are the Side Effects of Polymyxin B and Trimethoprim Ophthalmic?

Most people tolerate this medication well, but like all medicines, it can cause side effects. The good news is that serious side effects are uncommon since the medication stays mostly in your eye area.

Here are the most common side effects you might experience:

• Mild burning or stinging when you first apply the drops
• Temporary blurred vision for a few minutes after application
• Slight redness or irritation around the eye
• Increased tearing
• Feeling like something is in your eye

These common side effects usually fade within a few minutes of applying the drops and tend to become less noticeable as your body adjusts to the medication.

Though rare, some people may experience more serious side effects that require immediate medical attention:

• Severe eye pain or worsening infection
• New or worsening discharge from the eye
• Severe allergic reaction with swelling of face, lips, or throat
• Severe rash or hives
• Difficulty breathing

If you experience any of these serious side effects, stop using the medication and seek medical help right away. These reactions are uncommon but need prompt attention.

Who Should Not Take Polymyxin B and Trimethoprim Ophthalmic?

This medication isn't suitable for everyone, and your doctor will review your medical history before prescribing it. The most important consideration is whether you've had allergic reactions to either polymyxin B or trimethoprim in the past.

You should not use this medication if you have certain conditions or circumstances:

• Known allergy to polymyxin B, trimethoprim, or any ingredients in the drops
• Viral or fungal eye infections (this medication only treats bacterial infections)
• Mycobacterial infections of the eye
• Pregnancy or breastfeeding (unless your doctor determines the benefits outweigh the risks)

Your doctor will also use caution if you have kidney problems, though this is less of a concern with eye drops than with oral medications. Always tell your doctor about all your medical conditions and medications before starting treatment.

If you wear contact lenses, you'll need to remove them before applying the drops and wait at least 15 minutes before putting them back in. Many doctors recommend avoiding contact lenses entirely while treating an eye infection.

Polymyxin B and Trimethoprim Ophthalmic Brand Names

This combination is available under the brand name Polytrim, which is the most commonly prescribed version. You might also see it referred to simply as polymyxin B/trimethoprim ophthalmic solution.

Generic versions are also available and work just as effectively as the brand name. Your pharmacist might substitute a generic version unless your doctor specifically requests the brand name medication.

Whether you receive the brand name or generic version, the active ingredients and effectiveness remain the same. The main difference is usually the cost, with generic versions typically being less expensive.

Polymyxin B and Trimethoprim Ophthalmic Alternatives

If this medication doesn't work for your infection or you can't tolerate it, your doctor has several other antibiotic options available. The choice depends on the specific bacteria causing your infection and your individual medical situation.

Common alternatives include other antibiotic eye drops such as:

• Tobramycin ophthalmic (Tobrex)
• Ciprofloxacin ophthalmic (Ciloxan)
• Ofloxacin ophthalmic (Ocuflox)
• Erythromycin ophthalmic ointment
• Gentamicin ophthalmic drops

Your doctor might also consider combination products with different antibiotics or add anti-inflammatory medications if your infection is particularly severe. The key is finding the right medication that targets your specific bacteria while minimizing side effects.

Is Polymyxin B and Trimethoprim Ophthalmic Better Than Tobramycin?

Both medications are effective antibiotics for bacterial eye infections, but they work against different types of bacteria. Polymyxin B and trimethoprim combination targets a broader range of bacteria, while tobramycin is particularly effective against certain gram-negative bacteria.

The "better" choice depends on what's causing your specific infection. Your doctor might choose polymyxin B and trimethoprim if they suspect multiple types of bacteria or if previous treatments haven't worked. Tobramycin might be preferred for certain stubborn infections or if you've had reactions to other antibiotics.

Both medications have similar side effect profiles and are generally well-tolerated. Your doctor will consider factors like your infection type, medical history, and any previous antibiotic treatments when making their recommendation.