Alternatives to Polymyxin B/Trimethoprim If You Can't Fill Your Prescription

When your pharmacy can't fill a prescription for Polymyxin B/Trimethoprim (Polytrim) eye drops, it doesn't mean you're stuck without treatment. Several effective antibiotic eye drops treat the same conditions — bacterial conjunctivitis and blepharoconjunctivitis — and your doctor can switch your prescription quickly. Here's what to know about each option.

Why You Might Need an Alternative

Polymyxin B/Trimethoprim went through a supply disruption starting in 2023 after major manufacturer Akorn ceased operations. While Bausch Health and Sandoz have since stepped in, some pharmacies still experience temporary stock-outs. If you can't find it after checking multiple pharmacies (read: why Polymyxin B/Trimethoprim is hard to find), an alternative antibiotic eye drop may be the fastest path to treatment.

Alternative 1: Moxifloxacin (Vigamox, Moxeza)

Moxifloxacin ophthalmic solution is a fourth-generation fluoroquinolone antibiotic widely considered the gold standard for bacterial conjunctivitis by many eye care providers. Clinical trials have shown moxifloxacin achieves approximately 81% complete resolution at 48 hours, compared to 44% with Polymyxin B/Trimethoprim in some studies. It covers a broad spectrum of gram-positive and gram-negative bacteria, including Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae. Typical dosing is 1 drop three times daily for 7 days. The generic is available, though it's usually more expensive than generic Polytrim.

Alternative 2: Ciprofloxacin Ophthalmic (Ciloxan)

Ciprofloxacin ophthalmic (Ciloxan) is a fluoroquinolone antibiotic eye drop with broad-spectrum coverage. It's approved for both bacterial conjunctivitis and corneal ulcers, making it useful when there's any concern about corneal involvement. Ciprofloxacin ophthalmic has been available for decades and is generally well-stocked at most pharmacies. Dosing for conjunctivitis starts at 1–2 drops every 2 hours while awake for 2 days, then 1–2 drops every 4 hours for 5 more days. Generic ciprofloxacin eye drops are widely available and inexpensive.

Alternative 3: Ofloxacin Ophthalmic (Ocuflox)

Ofloxacin (Ocuflox) is an older fluoroquinolone that works similarly to ciprofloxacin. It's approved for bacterial conjunctivitis and corneal ulcers in patients 1 year and older. Like ciprofloxacin, it's been available as a generic for many years and tends to have broad pharmacy availability. Dosing for conjunctivitis is 1–2 drops every 2–4 hours while awake for the first 2 days, then every 4 hours for 5 more days. It can cause temporary stinging and light sensitivity, similar to other fluoroquinolones.

Alternative 4: Tobramycin Ophthalmic (Tobrex)

Tobramycin (Tobrex) is an aminoglycoside antibiotic eye drop with strong gram-negative coverage, including Pseudomonas aeruginosa. It's a reasonable choice for bacterial conjunctivitis, particularly when Pseudomonas is suspected (more common in contact lens wearers). Generic tobramycin is available. Standard dosing is 1–2 drops every 4 hours for 7–10 days, or 2 drops every hour during severe infections. It's often combined with dexamethasone (Tobradex) when inflammation is a concern, though that requires a more specific clinical indication.

Alternative 5: Erythromycin Ophthalmic Ointment

Erythromycin ophthalmic ointment (0.5%) is a macrolide antibiotic ointment sometimes used for mild bacterial conjunctivitis, especially in newborns and very young infants where fluoroquinolones may not be appropriate. It has decent gram-positive coverage but limited gram-negative spectrum. Typical dosing is a 1 cm ribbon of ointment applied to the affected eye(s) 2–6 times per day. It's less convenient than drops due to the ointment form causing temporary blurred vision, but it's widely available and inexpensive.

How to Compare These Alternatives

Here's a quick comparison of the most common alternatives:

Moxifloxacin: Broadest spectrum, fewer daily doses, faster resolution — but higher cost without insurance.

Ciprofloxacin: Well-stocked, affordable generic, also covers corneal ulcers — more frequent dosing required.

Ofloxacin: Similar to ciprofloxacin, older drug, widely available.

Tobramycin: Strong gram-negative coverage, good for contact lens wearers.

Erythromycin ointment: Best for infants and mild infections; ointment form less convenient.

A Note on Self-Treatment

All of these alternatives require a prescription in the United States. Do not try to use leftover antibiotic eye drops from a previous prescription — bacterial resistance is a real concern, and an old prescription may not cover the specific pathogen causing your current infection. Always talk to your doctor before switching medications.

The Bottom Line

If you can't find Polymyxin B/Trimethoprim, you have real options. Talk to your prescriber about switching to moxifloxacin, ciprofloxacin, or another antibiotic eye drop. Before giving up on Polytrim entirely, check out how to find Polymyxin B/Trimethoprim in stock — it may be available at a nearby pharmacy you haven't checked yet.