Understanding Polymyxin Eye Drops
Polymyxin B is an antibiotic medication primarily used to treat bacterial infections [1.4.1]. In ophthalmology, it is almost always found in a combination solution, most commonly with trimethoprim, under brand names like Polytrim [1.9.2]. This combination is prescribed to treat surface bacterial infections of the eye, such as bacterial conjunctivitis (pink eye) and blepharoconjunctivitis, which is an infection of the eyelid and conjunctiva [1.3.5, 1.3.6].
How Do They Work?
Polymyxin B and trimethoprim work together to eliminate bacteria through a dual-action mechanism [1.4.5, 1.4.6]:
- Polymyxin B: This antibiotic is bactericidal, meaning it kills bacteria. It targets gram-negative bacteria, like Pseudomonas aeruginosa, by disrupting their cell membranes, causing the cellular contents to leak out [1.3.1, 1.4.6].
- Trimethoprim: This component is bacteriostatic, meaning it stops bacteria from reproducing. It blocks an enzyme called dihydrofolate reductase, which prevents bacteria from synthesizing essential proteins and nucleic acids [1.3.1, 1.4.5].
This combination provides broad-spectrum coverage against common eye pathogens, including Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae [1.3.1].
Are Polymyxin Eye Drops Safe?
When used topically in the eye as directed by a healthcare provider, polymyxin B combination drops are considered safe for adults and children as young as 2 months old [1.3.4, 1.9.3]. The key is proper use for the prescribed duration, typically one drop every three hours for 7 to 10 days [1.9.1].
Systemic absorption (the drug entering the bloodstream) is minimal with ophthalmic use, so serious internal side effects are not expected [1.3.1, 1.2.5]. The main concerns are local reactions and the potential for developing antibiotic resistance if used improperly.
Potential Side Effects
Most side effects are mild, temporary, and localized to the eye. They may include:
- Burning, stinging, or itching upon instillation [1.2.1, 1.2.4]
- Increased redness and tearing [1.2.2, 1.2.6]
- Temporary blurred vision [1.2.5]
- Eyelid swelling or itching [1.2.2]
These minor effects often resolve on their own. However, if they persist or worsen, you should contact your doctor [1.2.1].
Serious Reactions and Precautions
While rare, serious side effects can occur. It is crucial to stop using the medication and seek immediate medical help if you experience signs of a severe allergic reaction [1.2.3, 1.3.2]:
- Skin rash, hives, or itching
- Swelling of the face, lips, tongue, or throat
- Difficulty breathing or wheezing
- New or worsening eye pain or discharge [1.2.1]
Prolonged use beyond the prescribed period can lead to a secondary infection, such as a fungal infection in the eye [1.2.3, 1.3.2]. It is also important not to use these drops to treat viral or fungal eye infections, as they will be ineffective and could worsen the condition [1.9.2]. Polymyxin eye drops are contraindicated for individuals with a known hypersensitivity to any of its components [1.3.1].
How to Use Polymyxin Eye Drops Correctly
Proper administration is vital for safety and effectiveness. Always follow the specific instructions from your doctor or pharmacist [1.9.1].
- Wash Hands: Thoroughly wash your hands with soap and water [1.8.1].
- Prepare: Do not let the dropper tip touch your eye, fingers, or any other surface to avoid contamination [1.8.1, 1.9.1]. If you wear contact lenses, remove them before use and wait at least 15 minutes after application before reinserting them [1.2.5, 1.9.3].
- Instill: Tilt your head back, pull down your lower eyelid to create a small pocket, and squeeze one drop into it [1.8.1, 1.9.1].
- Absorb: Close your eye and gently press a finger on the inner corner (near the nose) for 1-2 minutes. This prevents the medication from draining into your tear duct and enhances absorption in the eye [1.8.1, 1.8.4].
- Complete the Course: Use the medication for the full prescribed duration, even if your symptoms improve, to prevent the infection from returning and to reduce the risk of antibiotic resistance [1.3.2, 1.9.1].
Comparison with Other Antibiotic Eye Drops
Polymyxin B/trimethoprim is one of many options for treating bacterial eye infections. Here's how it compares to other common choices:
| Feature | Polymyxin B/Trimethoprim (Polytrim) | Ofloxacin (Ocuflox) | Tobramycin (Tobrex) |
|---|---|---|---|
| Antibiotic Class | Polypeptide & Folic Acid Antagonist | Fluoroquinolone | Aminoglycoside |
| Primary Use | Bacterial conjunctivitis, blepharoconjunctivitis [1.3.1] | Bacterial conjunctivitis, corneal ulcers [1.6.1] | Various bacterial eye infections [1.6.5] |
| Spectrum | Broad-spectrum against gram-positive and gram-negative bacteria [1.3.1] | Broad-spectrum, particularly effective for corneal ulcers [1.6.2] | Primarily targets gram-negative bacteria [1.5.4] |
| Common Side Effects | Local irritation, stinging, redness [1.2.6] | Temporary burning sensation, light sensitivity [1.6.1] | Eyelid itching and swelling, eye redness [1.6.5] |
| Age Approval | 2 months and older [1.3.4] | 1 year and older [1.6.1] | 2 months and older [1.6.5] |
Conclusion
Polymyxin eye drops, specifically in combination with trimethoprim, are a safe and well-established treatment for common bacterial eye infections when used correctly under a doctor's supervision [1.3.6, 1.9.2]. While minor side effects like stinging and redness are common, severe reactions are rare [1.2.1, 1.3.2]. Adhering to the prescribed dosage, duration, and proper administration techniques is essential to maximize efficacy and minimize risks, including the development of antibiotic resistance [1.9.1]. If your symptoms do not improve or you experience signs of an allergic reaction, consult your healthcare provider promptly [1.9.2].
For more information from an authoritative source, you can visit MedlinePlus.
