Gentamicin - Ophthalmic

By Lauren Forsythe, PharmD, DICVP; Rania Gollakner, BS, DVM, MPH

What is gentamicin?

Gentamicin (brand names: Genoptic®, Gentak®) is a topical, aminoglycoside antibiotic used to treat certain bacterial infections. It can also be used to treat end-stage glaucoma (increased eye pressure).

Its use in cats and dogs to treat bacterial infections in the eye and glaucoma is sometimes “off label” or “extra label”. Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is gentamicin given?

Gentamicin can be found in many forms, but for the eye it is given as an ointment or liquid solution.

  • Gentamicin is applied directly to the eye to treat infections. 
  • Do not touch the tip of the bottle or tube to the eye or any other surface. 
  • Do not apply this medication within 5 minutes of administering another medication in the eye. 
  • Keep the cap tightly closed when not using the medication. This medication will take effect quickly, in about 1 to 2 hours, but outward effects may take a few days to be recognized.

For the treatment of glaucoma, your veterinarian will administer the medication during a surgical procedure in hospital.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember. However, if it is close to the time for the next dose, skip the dose you missed, give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Side effects of this medication include:

  • eye irritation and burning
  • redness or mild swelling of the tissue around the eye

If these side effects occur, discontinue the medication and contact your veterinarian. Rarely, allergic reactions and thrombocytopenic purpura (bruising and bleeding) can occur.

This short-acting medication should stop working within 24 hours.

Are there any risk factors for this medication?

Gentamicin should not be used in patients that have:

  • a history of hypersensitivity or allergy to it, or
  • a full thickness wound in the eye.

Are there any drug interactions I should be aware of?

Drug interactions have not been noted at this time with topical use of gentamicin.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working. Your pet should be rechecked before treatment is discontinued.

How do I store gentamicin?

  • Store gentamicin in the refrigerator or at controlled room temperature, as indicated on the label.
  • Protect gentamicin from moisture, sunlight, and freezing.
  • Do not use if the color changes, it becomes cloudy, or if particles (grit) are seen in the solution.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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