Oxytetracycline Ophthalmic for Cow: Pinkeye 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 ophthalmic is a prescription antibiotic eye ointment used on the surface of the eye. In the U.S., the best-known product is Terramycin, which contains oxytetracycline hydrochloride and polymyxin B sulfate. Oxytetracycline is a tetracycline-class antibiotic, while polymyxin B adds coverage against certain gram-negative bacteria. The ointment is FDA-approved for use in cattle and sheep for pinkeye treatment, and the label also includes several other species for superficial ocular infections.

In cattle, this medication is most often discussed in relation to infectious bovine keratoconjunctivitis (IBK), commonly called pinkeye. Merck Veterinary Manual notes that pinkeye in cattle often causes tearing, squinting, light sensitivity, and corneal ulceration, and that early treatment matters because severe cases can progress to marked corneal opacity, perforation, or permanent vision loss.

Because this is an eye medication, clean handling matters. The tube tip should not touch the eye, eyelids, hair, chute, or your hands. Contamination can worsen infection or introduce new bacteria. Your vet may also pair the ointment with herd-level management steps such as fly control, shade, dust reduction, and separating affected cattle when practical.

In cows, oxytetracycline ophthalmic is used most commonly for pinkeye caused by bacteria susceptible to the medication, especially when your vet wants a topical option applied directly to the eye. Merck Veterinary Manual specifically states that topical oxytetracycline ophthalmic ointment is approved for pinkeye treatment in cattle. Pinkeye outbreaks are often linked with warm weather, flies, dust, plant irritation, and ultraviolet light exposure.

Your vet may recommend it for mild to moderate superficial eye infections, conjunctivitis, keratitis, or as part of a treatment plan when there is a corneal ulcer and bacterial infection is suspected or confirmed. The product label also lists superficial ocular infections due to susceptible organisms, including conjunctivitis, keratitis, pink eye, corneal ulcer, and blepharitis.

That said, not every red or cloudy eye is a straightforward pinkeye case. Foreign bodies, parasites, trauma, severe ulcers, and deeper eye disease can look similar at first. If a cow has a very cloudy eye, obvious ulcer, severe pain, or reduced vision, your vet may recommend a different plan, such as systemic antibiotics, pain control, an eye patch, or other procedures that fit the severity and handling realities of the herd.

Use oxytetracycline ophthalmic only as directed by your vet. The current Terramycin prescribing information states the ointment should be administered topically to the eye 2 to 4 times daily. Merck Veterinary Manual adds an important practical point for herd medicine: topical ointments generally need to be applied at least every 8 to 12 hours to be effective, which can be hard to maintain in some cattle operations.

In real-world cattle care, dosing decisions depend on the number of affected animals, severity of disease, whether one or both eyes are involved, and how safely the animal can be restrained. Your vet may have you clean discharge away first, then place a ribbon of ointment inside the lower eyelid without touching the tube tip to the eye. Treatment is usually continued for the full course your vet recommends, even if the eye looks better sooner.

If a dose is missed, contact your vet for guidance rather than doubling up. Recheck is important if the eye becomes more opaque, the ulcer appears deeper, the cow stops eating, or there is no clear improvement within a short time frame. Pinkeye can worsen fast, and some cases need a more practical herd-level option than repeated topical treatment.

Most cattle tolerate oxytetracycline ophthalmic reasonably well, but mild local irritation can happen. After application, some animals may squint more for a short time, blink, rub the eye, or show temporary redness. With any eye ointment, a little residue on the lashes or eyelids is common.

More serious reactions are uncommon, but they matter. The Terramycin label warns that serious hypersensitivity reactions have been reported after antibiotic ophthalmic preparations. While the label example highlights cats, the broader point still applies: if an animal develops facial swelling, hives, weakness, vomiting, breathing trouble, or sudden worsening after treatment, stop the medication and contact your vet immediately.

There is also a treatment-related risk that matters in herd medicine: using antibiotics can allow resistant or nonsusceptible organisms, including fungi, to overgrow. If the eye looks worse instead of better, develops unusual discharge, or fails to improve as expected, your vet may want to reassess the diagnosis. A worsening eye is not something to watch for days at home.

There are no widely emphasized major systemic drug interactions for topical oxytetracycline/polymyxin B ophthalmic when it is used in the eye as labeled. Because absorption from the eye surface is limited, interaction concerns are usually lower than with injectable antibiotics. Still, your vet should know about all medications and eye products the cow is receiving, including injectable antibiotics, anti-inflammatories, fly-control products used near the face, and any compounded eye medications.

If more than one eye medication is prescribed, the order and timing matter. VCA advises spacing eye medications apart and giving drops before ointments, because ointments can block later medications from reaching the eye surface well. Your vet may also avoid combining this ointment with products that could irritate an already ulcerated cornea or make it harder to monitor healing.

One more practical caution: in food animals, medication choices are shaped not only by biology but also by label restrictions and extra-label drug rules. Merck and FDA both note that extra-label antimicrobial use in food-producing animals has legal limits. That is one more reason to check with your vet before layering treatments or substituting products.