Gentamicin - Otic

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

What is gentamicin?

Gentamicin (brand names: Gentocin®, Genoptic®, Gentak®) is an aminoglycoside antibiotic used to treat certain bacterial ear infections.

Its use in cats and dogs to treat bacterial infections in the ears 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.

Some eye medications may be used off-label in the ear. Ensure you are administering the drops to the site indicated by your veterinarian.

Gentamicin is commonly used with other products to compound ear drops specifically for the infection your pet has, so your pet’s gentamicin-otic may be a compounded product.

How is gentamicin given?

Gentamicin can be found in many forms, but for the ears, it is given as an ointment, suspension, or ophthalmic solution that is used off label to treat ear infections.

  • Gentamicin is applied dropwise directly to the ear canal.
  • Ensure you follow your veterinarian’s directions regarding the appropriate sequence of ear cleaning in relation to administering this medication.
  • If giving this medication in both ears, ensure a designated syringe is used for each ear to prevent transferring infection between ears.
  • When using this medication with acidifying ear cleaners and/or aminoglycoside or fluoroquinolone-containing agents, administer this product an hour apart from these other treatments.

In veterinary-labeled products for otic use, gentamicin is only found in combination with other drugs, such as steroids and antifungals. Examples of these products include Mometamax®, Otomax®, Gentamicin Gentizol®, Vetromax®, MalOtic®, Otibiotic®, or Tri-Otic®.

What if I miss giving my pet the medication or my shipment is late?

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 gentamicin include redness or increased inflammation. If this occurs, discontinue the medication, and contact your veterinarian.

Are there any risk factors for this medication?

Gentamicin should not be used in patients with a history of hypersensitivity or an allergy to it.

Are there any drug interactions I should be aware of?

Drug interactions have not been noted with topical use of gentamicin at this time. 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.
  • Store away from moisture and sunlight.
  • Do not freeze.
  • If the medication is compounded, dispose of any leftover medication once the expiration date on the label is reached.
  • Do not use if the color changes, it becomes cloudy, or if particles 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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