Oxytetracycline/Polymyxin B Eye Ointment for Sheep: Uses & Side Effects

This information is for educational purposes only. Never give your pet any medication without your veterinarian's guidance. Dosing, frequency, and safety depend on your pet's specific health profile.

Oxytetracycline/polymyxin B ophthalmic ointment is a prescription eye medication used in several animal species, including sheep. The best-known brand is Terramycin® Ophthalmic Ointment. It combines two antibiotics in a petrolatum base: oxytetracycline, a broad-spectrum tetracycline antibiotic, and polymyxin B, which adds activity against certain gram-negative bacteria.

In the FDA-approved veterinary label, each gram contains 5 mg oxytetracycline hydrochloride and 10,000 units of polymyxin B sulfate. The ointment is applied directly to the eye rather than given by mouth or injection. Because it stays on the eye surface longer than drops, it can be useful when your vet wants local antibiotic coverage for superficial eye disease.

For sheep, this medication is commonly discussed in the setting of pinkeye, also called infectious keratoconjunctivitis. Merck Veterinary Manual notes that topical oxytetracycline/polymyxin B ophthalmic ointment is approved for pinkeye treatment in cattle and sheep. That said, not every red or cloudy eye is a bacterial infection. Trauma, foreign material, ulcers, entropion, and severe irritation can look similar, so your vet should confirm what problem is most likely before treatment starts.

Eye disease in sheep can worsen quickly. A painful eye may shut tightly, tear heavily, or develop a white or blue haze over the cornea. If you notice those signs, or if vision seems affected, contact your vet promptly rather than trying to sort it out on your own.

This ointment is used for superficial ocular infections caused by susceptible bacteria. The FDA label lists conditions such as conjunctivitis, keratitis, pink eye, corneal ulcer, and blepharitis in dogs, cats, cattle, sheep, and horses. In sheep practice, the most common reason your vet may reach for it is pinkeye, especially when the eye is inflamed, tearing, and sensitive to light.

Pinkeye in sheep is not one single disease pattern. It can involve bacteria, irritation from dust or plant material, face flies, ultraviolet light exposure, or a combination of factors. Because of that, your vet may use this ointment as one part of a larger plan that can also include isolation, fly control, pain management, stain testing for ulcers, and follow-up checks.

This medication is not a cure-all for every eye problem. Antibiotic ointment will not fix a foreign body stuck under the eyelid, eyelid abnormalities, deep corneal injury, or nonbacterial causes by itself. If the eye looks very cloudy, bulging, severely ulcerated, or the sheep seems systemically ill, your vet may recommend a different or more intensive approach.

It is also worth knowing that food-animal rules matter. Sheep are food-producing animals, so medication choices, routes, and timing should always be guided by your vet with attention to legal use and any applicable withdrawal instructions.

The FDA label for Terramycin® Ophthalmic Ointment states that it should be applied topically to the eye 2 to 4 times daily. Merck Veterinary Manual notes that topical ointments for pinkeye in cattle and small ruminants generally need to be applied at least every 8 to 12 hours to be effective. In real life, the exact schedule depends on how severe the eye problem is, whether one or both eyes are affected, and how practical repeat handling is for your flock.

Your vet will tell you how much ointment to place and how long to continue treatment. A common ophthalmic approach is a small ribbon of ointment inside the lower eyelid, taking care not to touch the tube tip to the eye, wool, skin, or hands. If the tip becomes contaminated, bacteria can be introduced back into the eye the next time the medication is used.

Before applying the ointment, gently wipe away discharge with clean gauze if your vet has advised that. After treatment, keep the sheep in a low-dust area if possible and reduce fly exposure. If your vet has prescribed more than one eye medication, ask about the order and spacing. In many species, drops are usually given before ointments, with several minutes between products.

Do not stop early because the eye looks a little better after a day or two. On the other hand, do not keep using leftover ointment for a new eye problem without veterinary guidance. If the eye is more painful, more cloudy, or not clearly improving within the timeline your vet gave you, recheck the sheep promptly.

Most sheep tolerate ophthalmic antibiotic ointments reasonably well, but mild local reactions can happen. With oxytetracycline/polymyxin B products, veterinary references describe possible temporary irritation, stinging, itching, swelling, or increased redness around the eye after application. Some animals may blink more for a short time right after the ointment is placed.

A more important concern is hypersensitivity or allergy to one of the ingredients. VCA notes that allergic-type reactions can include facial swelling, rash, fever, puffiness, or trouble breathing, although these are uncommon. If your sheep seems suddenly worse after treatment, stop and contact your vet right away.

Another issue is treatment failure rather than a classic side effect. The label warns that antibiotic use can allow overgrowth of resistant or nonsusceptible organisms, including fungi or other bacteria, if the original problem is not responsive to the medication. That means a persistently cloudy, painful, or worsening eye needs a recheck instead of repeated unsupervised dosing.

See your vet immediately if the eye is held shut, the cornea looks white or blue, there is a visible ulcer or puncture, discharge becomes heavy, or the sheep seems unable to see. Those signs can point to a more serious eye injury that needs prompt veterinary care.

No major drug interactions are commonly reported for oxytetracycline/polymyxin B ophthalmic ointment in routine veterinary use. VCA specifically notes that no known drug interactions have been reported for this medication. Even so, your vet still needs a full medication list, especially in food animals where treatment records and legal use matter.

The more practical issue is how this ointment is combined with other eye medications. If your sheep is also receiving eye drops, stain tests, pain-relief medication, or another topical product, ask your vet about the order and timing. In general ophthalmic practice, drops are usually applied first and ointments second, with a short gap between them so one product does not immediately dilute the other.

Avoid layering over-the-counter eye products, steroid-containing eye medications, or leftover livestock medications unless your vet has specifically approved them. Some eye problems, especially corneal ulcers, can worsen if the wrong product is used. That is one reason a veterinary eye exam matters before mixing treatments.

Because sheep are food-producing animals, also ask your vet whether any companion medications change handling, monitoring, or withdrawal planning for the flock. A clear written treatment plan helps prevent dosing mistakes and keeps records accurate.