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Gentamicin is a powerful, broad-spectrum antibiotic that is often used to treat bacterial infections, including those that have resisted other antibiotic treatments. While used most often for dogs and cats, gentamicin antibiotics can also help treat infections in other animals, such as rabbits.

Sold under various brand names, including Gentocin, Genoptic and Gentak, gentamicin is an aminoglycoside that works by suppressing protein synthesis within the bacteria. Veterinarians typically use gentamicin for cats and dogs to stop stubborn bacterial infections from growing.

What does gentamicin treat?

Gentamicin for dogs and cats can help kill gram-negative aerobic bacteria and can be used to treat a variety of infections, including:

  • Ear infections
  • Sinus infections
  • Bladder infections
  • Infected wounds
  • Respiratory infections
  • Bloodstream infections
  • Skin infections
  • Pneumonia

Your veterinarian must prescribe gentamicin antibiotics. Always discuss medications with your veterinarian before giving them to your pet. You can obtain gentamicin with a prescription from Petco’s dog pharmacy or cat pharmacy.

How do I administer gentamicin to my pets?

The drug can be administered in several different ways depending on the pet’s condition and what form of the medication they’ve been prescribed. Gentamicin injections for dogs and cats can be administered in a veterinary office. They can be given under the skin—subcutaneously—or within the muscle—intramuscularly. Vets can also administer gentamicin infusions.

Gentamicin can also be prescribed as a spray or ointment. Gentamicin spray for cats and dogs is used to treat a variety of bacterial skin infections, while gentamicin ointment for dogs and cats can be applied to the eyes or ears to treat ear and eye infections. Note that eye and ear formulations are different and should only be used in locations it’s formulated for. In some cases, vets will prescribe gentamicin ointment for dogs’ ears and cats’ ears extra-label. It is common for veterinarians to prescribe medications extra-label, but always follow your vet’s instructions carefully, as the directions on the prescription may not apply to your pet’s specific situation.

Are you looking for a veterinarian to treat your pet and prescribe the proper medication for their injury or illness? Many neighborhood Petco Pet Care Centers include veterinary services. Check your local store to find out if you can get a prescription for gentamicin spray for dogs and cats or any other medication your pet may need.

Is gentamicin safe for cats and dogs?

When used as prescribed by your veterinarian, gentamicin is generally safe for cats, dogs and small pets. Of course, you should always watch your pet closely after starting them on a new medication and alert your vet if you notice any problems.

Gentamicin antibiotic is not suggested for pets with known allergies to the drug or who are hypersensitive. Additionally, it should not be given to pregnant or nursing pets.

The most common gentamicin side effects include kidney damage, hearing loss, loss of balance, liver disorders, upset stomach and red and irritated skin. In large doses, gentamicin for dogs side effects can cause muscle paralysis. The same can happen in cats who receive too much of the drug.

Long-term kidney damage is one of the most severe side effects of gentamicin. The longer your pet is on gentamicin and the higher the dose, the greater the risk of kidney damage becomes. Your vet may check your pet’s kidney health before prescribing the antibiotic.

Additionally, due to the drug’s potential to cause hearing loss, gentamicin should not be used for animals who use their hearing in a professional capacity—such as police dogs, military dogs, rescue dogs, guide dogs and more.

Always talk to your veterinarian about possible gentamicin side effects before administering it to your pet. You should also let your vet know if your pet is on any other medications, supplements or vitamins, as they may interact adversely with gentamicin.

Pet prescriptions available to order at Petco

How much gentamicin should I give my dog or cat?

Always follow your vet’s instructions on how much gentamicin antibiotic to give your cat, dog or other pet. The dosage will depend on your pet’s size, age, health and the condition being treated.

Topical doses will depend on the animal’s condition and size, though pet parents can expect to medicate their pet one to three times each day.

What should I do if I miss my pet’s dose of gentamicin?

If you’ve only missed your pet’s medication dose by a few hours, go ahead and give your pet the missed dose and continue their medication schedule as usual. If you are close to your pet’s next dose, skip the missed dose and continue with the regular dosing schedule. Do not double your pet’s dose of gentamicin antibiotic or try to spread the missing amount over future doses.

How long do I continue gentamicin for dogs or cats?

The length of your pet’s gentamicin treatment course will depend on your pet’s condition, the severity of the disease and what form of gentamicin your veterinarian prescribes. Make sure to complete the entire course of treatment as advised by your vet. Even if your pet seems to be getting better, do not stop treatment early, as this might cause the condition to return or even contribute to the bacteria becoming antibiotic-resistant.

If you think your pet is fully healed before the treatment is complete, contact your veterinarian to discuss appropriate next steps for your pet.

How do I store gentamicin?

The storage requirements of gentamicin for cats and dogs depends on the formulation of the medication. Check the label of your gentamicin or speak to your veterinarian about the proper way to store your medicine. In some cases, you can store gentamicin at room temperature, while other drug versions need to be refrigerated. Keep your medication out of direct sunlight and away from moisture. If you notice that your medication has changed color or become cloudy, do not give it to your pet. Instead, renew your prescription at your veterinarian’s office or pharmacy.

How do I give my pet gentamicin eye drops? If your pet has conjunctivitis, keratitis or another bacterial eye infection, your vet may prescribe gentamicin eye drops. Even the gentlest feline or canine may be difficult when you try to administer eye drops. Proceed slowly and cautiously.

First, read the instructions of the gentamicin antibiotic carefully and make sure you know exactly how much to give your pet. Wash your hands thoroughly before applying any medication to your pet’s eyes. If your pet has debris around their eyes, wash them with an eye wipe or use sterile eye wash to clean the area. Never wipe your pet’s eyes with a dry cloth.

If your pet is anxious, you may need to ask for help from another person to hold or restrain your pet or invest in a calming supplement. For cats and smaller dogs, you can try wrapping them gently in a towel or blanket to help secure them.

Hold the eye drop bottle in your dominant hand between your thumb and index finger. Hold the bottle in your dominant hand. Place the same hand on your pet's forehead to steady them, gently pull back the upper eyelid (for cats) or lower eyelid (for dogs), then administer the prescribed number of drops. Aim the medication in the center of the eye. Your pet will blink, which will help spread the medicine.

Praise your pet throughout the procedure and give them a treat when it is complete.

How do I give my pet gentamicin ear drops?

Giving your pet ear drops is similar in many ways to giving them eye drops. Dogs and cats can develop bacterial ear infections. Bacteria love warm, moist environments and will thrive in ear canals if given the chance. This is especially true for dogs with floppy ears who love playing in the water.

Wash your hands thoroughly before giving your pet gentamicin ear drops. If your pet has debris in their ears, carefully use ear wipes or pet ear cleaner and a cotton ball or tissue to wipe out debris. Remember that ear infections can be painful for your pet, so even the friendliest dog or cat may fight when you get near their swollen ear. Aggressive behavior may ease over time as your pet’s infection lessens.

If you have another adult in your home, you may want to enlist them to help restrain your pet. Use positive reinforcement with treats and praise as you coax your pet and administer the medicine. Consider gently wrapping cats or smaller dogs in a towel or blanket. Holding them in your lap may be helpful.

Hold the bottle or dropper in your dominant hand. Use your other hand to hold open your pet’s ear canal. Release the appropriate amount of drops slowly. If your pet will allow it, massage the base of the ear to help spread the medication. If your pet’s ear infection is painful, they may not allow it, but that’s OK. Give your pet lots of praise and treats after you’ve given them the gentamicin antibiotic.

Giving your pet ear drops may be challenging, but knowing that you are helping them feel better makes the difficulties well worth it.

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Reviewed by Dr. Whitney Miller, DVM, MBA, DACVPM

As Petco’s Chief Veterinarian, Dr. Miller is the lead veterinary subject matter expert, overseeing the company’s standards of excellence in animal care and welfare, growth in pet services and much more. Dr. Miller leads Petco’s medical team, supporting over 200 full-service hospitals and mobile vaccination clinics operating in over 1,000 Petco Pet Care Centers nationwide