What You Must Know Before Giving Your Dog Bactrim!

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Prescription Bactrim is a popular antibiotic for humans, but is this drug is OK for a dog’s bacterial infection?

Too dangerous? Just how risky is it?

Here’s the deal:

Can I Give My Dog Bactrim?Pets generally respond well to Bactrim. It works for dogs too. However, this type of treatment requires a vet’s expertise.

Dogs Can Take Bactrim

It is fairly safe following a diagnosis, vet’s authorization and their detailed instructions.

Bactrim is actually well-utilized for treating dogs.

At the same time, there are well-documented side effects. Don’t chance it!

9-Year Study’s Findings

Utrecht University did a retrospective analysis of trimethoprim-sulphonamide (T-S) combinations on 19 dogs.

The results?

Dermatological and systemic reactions were confirmed. It’s the nature of antibiotics.

The good news is the adverse reaction incidence rate was only 0.25%

Cautious K9 Treatment

Despite the risks, this drug is very effective for urinary tract infections (UTIs).

Basically, Bactrim inhibits growth of harmful microorganisms. Then, it kills them off!

It can also be given to dogs for:

  • Cystitis
  • Certain skin infection
  • Kennel cough
  • Pneumonia

Warning: Never give Bactrim to a pregnant or lactating dog or those suffering from a liver or kidney disease.


Know The Side Effects

Bactrim can cause poisoning, hypersensitivity and various allergic reactions.

Serious complications are possible.

Common canine complications include diarrhea and vomiting.

Your dog may also:

  • Get a rash
  • Have reduced appetite
  • Have difficulty breathing
  • Have swelling of the tongue, lips and/or face

That’s not all…

Watch for signs of blood in their stool and urine (a sign of internal bleeding).

A strong indicator of liver damage would be if your dog’s eyes are yellowish after taking Bactrim or any broad spectrum antibiotic.

Bactrim Dosing Info

It’s important to provide your dog with an appropriate Bactrim dose.

Talk with a veterinarian for the correct amount (as well as the treatment’s duration).

Several factors go into determining a dose. These include:

  • Overall health
  • Breed
  • The dog’s age
  • Their size (weight)
  • The type of infection and;
  • The pet’s response to the drug

A wide range of 12mg to 50mg per pound of Bactrim is considered acceptable.

But again, dosing depends on the dog’s particular situation.

Your vet may recommend increasing (or decreasing) dosage at a later time. Follow that advice!

Delivering This Drug

There are several ways to give Bactrim or generic equivalent.

The most popular way to administer this antibiotic is to crush up tablets. This way you can mix the contents with dog food.

Pressing the pill down your dog’s throat is another option (assuming you’re comfortable doing so).


FYI: Sometimes Bactrim needs to be provided intravenously, intramuscularly or subcutaneously.


Taken With Other Meds

There are also contraindications associated with taking Bactrim.

Yes, this applies to dogs too!

Aspirin, for example, should not be taken with Trimethoprim/sulfamethoxazole.

Starting to see that Bactrim treatment isn’t so simple?

The Bottom Line

Bactrim is considered safe enough for dogs (when it’s used responsibly).

Vets prescribe this antibiotic for various infections, but a diagnosis is an absolute must.

You must be very familiar with side effects.

And monitoring of your dog is essential while they are on this prescription and never, ever administer your own supply of Bactrim.

What Do You Think? Have Your Say Below…

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22 thoughts on “What You Must Know Before Giving Your Dog Bactrim!”

  1. My 5 year old Miniature Schnauzer was given Bactrim for Kennel Cough. It caused liver failure and kidney failure within 2 weeks. He passed away. Do not let a vet prescribe Bactrim.

  2. My German Shepherd was on this drug for 3 weeks. I presented him to the vet during the course of treatment with lethargy, difficulty holding urine and disorientation.

    They did a blood panel and his thyroid levels are low, he’s anemic, and his kidney function is not normal. Urine is highly concentrated. They did a kidney disease test and that came back negative.

    They are trying to blame this on his pain medications, but everything I am reading is pointing to sulfa drug toxicity. What is the treatment for this? Should I take him to another vet?

  3. I have a 13 year old Poodle with a bladder infection. I started her on Bactrim (600mg). Should I give that med once a day or 300mg twice daily?

  4. My dog was recently bitten on his cheek. I checked for wounds and saw none, but it now seems to be infected. He’s a 1 year old Heeler Cattle Bully mix and weighs anywhere from 40 to 55 pounds.

    I recently had my funds drained and cannot afford a vet. I’ve scrapped up what I have and still don’t have enough. I do have bactrim tablets from a spider bite from another time. Will using small amounts, small amounts, start helping with the infection?

  5. My dog has been on this medicine for almost a week. I have taken him off all the rest of his meds and he continues to get more and more lethargic, his back legs are giving out on him. By the time he is ready for his next dose he is walking, then withing an hour he can barely walk. He was taking the medication for a cyst, prescribed by a veterinarian.

    1. Trimethroprim sulfa has caused liver damage and death in Dalmatians and Vizsla dogs. Please ask your vet to properly research this commonly used antibiotic.

    2. This is happening to my Great Dane, but he’s off of this med. Should I continue this medication?

  6. I have a dog with a small wound in his neck. It has, in the last 10 hours, swollen to the size of a softball. My dog is a Pit bull Labrador Retriever mix so he’s quite big. I can’t afford a vet visit right now and have Bactrim DS on hand from my last ear infection. Can I give him that and at what dosage?

    1. I would not give him any medication without knowing what is wrong with him. It could make the problem worse. How about some cold wet towels (not ice) held on the area to reduce swelling. He is going to need a veterinarian. Call your local humane society. They usually have low or even no cost services. Another option is to turn him over to a rescue group. He needs medical attention.

  7. I have a 1 year old Lab. His ears keep bothering him, scratching and shacking his head. A vet said it was a yeast infection. Can I give him Bactrim? I do not have the money to take him to a vet right now.

    1. Bactrim won’t help because it is not effective at all against yeast infections. It might even make the yeast infection worse because it can kill the normal bacteria that live in your dog’s ears. Buy an over-the-counter ear cleanser for dogs. I use a Burt’s Bees product daily according to the directions.

      I clean my Beagle’s ears daily when they smell musty and a couple of times a week just to keep them healthy. Don’t ignore the yeast infection as it is painful for the dog and can lead to deafness if left untreated. Continuous cleaning with a good product should help.

    2. Buy a small bottle of apple cider vinegar and mix it 50/50 with water. Then just pour a couple of teaspoons of that in his ear and let it sit. Put a cotton ball down in his ear for absorption. You should take him to a vet if it doesn’t clear up soon. You can do this procedure every day for about a week. If it’s not gone by then, he needs to go to the vet.

  8. I have two month old Labrador puppy. He is healthy with a good immune system but is suffering from a skin infection, not a boil but welt, in one of his eyes. I gave him Cefpet 50mg, Cefpodoxime Proxetil, for 4 days but there is no relief. Can I give him Bactrim and what is the proper dose? Please help.

    1. I have a Lab/Pit mix and he has had the same issue as your dog. I had him on Bactrim. The pill was an 800mg but I cut that in half and gave it to him twice a day. Due to the size of your puppy, you may want to cut that size in half.

      Also, pay close attention to ensure that your dog doesn’t have an allergic reaction like difficulty breathing or swollen tongue. If so, stop giving it to him. While on the med, have your dog drink plenty of water. Good luck.

  9. My 9 year old female Dachshund (about 16 pounds) was given Bactrim two weeks ago for a staff infection after several other antibiotics didn’t help. Now she is extremely lethargic with a loss of appetite and seems to not want to walk anymore than necessary, even when she has to go outside.

    I’m taking her back to the vet today, but have you any suggestions, as he seems to be having a problem helping her. Surgery and a biopsy gave no diagnosis.

  10. Bridgette says:

    My dog was given Bactrim for kennel cough and it has hurt his joints in his back legs. The vet discontinued it, but the damage has been done. I saw him lowering himself to the ground and I thought he was sick. Then he wouldn’t sit down at all. I finally got him to lay down, I thought he was dying.

    I cried and prayed and he got a little better. I took him back to the vet and he told me to stop the antibiotic. I did and he came out of it, but now has trouble getting up on the couch and things. His back hips obviously hurt him. Now I’m looking for steps and joint lubricating substances, guilt ridden for what I subjected my dog to. I would ask for Amoxicillin if given Bactrim.

  11. My little Maltese is 13 years old and has suffered forever with skin irritation and tropical ear infections. I have taken her to numerous vets and yet they have never gotten to the bottom of her problems or given her anything to cure her. I believe Bactim is good for these ailments. Is this true? I started her today on a small amount. Is this safe for my little aging dog?

    1. Debbie, I’m surprised none of the vets have ever prescribed Bactrim for your dog before. It’s worth a try because it is a fairly common treatment option. I hope it helps.

      1. How many milligrams of bactrim did you give your dog? I have a Beagle with an ear infection and have bactrim on hand from a previous treatment. Your suggestion would be greatly helpful and appreciated.

  12. Annemarie says:

    I need some info on Bactrim for my 4 year old who we got when he was just a pup. He was treated for a bacterial skin infection a year or so ago with another antibiotic. The wet wipes we use on his creases as a daily routine has worked the best and is very effective in keeping the bacteria to a minimum on his skin.

    Now we are not sure if we have some sort of Auto-immune condition of some sort of bone marrow cancer/condition. Should we use Bactrim prophetically to prevent any new infection or do we try another medication option that is more expensive and has fewer side effects. But again I ask what is known about Bactrim use and the side effects in dogs.

  13. My friends dog is dying from this. His immune system was destroyed. Don’t chance it. There are better, safer antibiotics out there. This is a last resort antibiotic.

  14. My dog is dying because of this drug. If your dog is older make sure your vet dose a simple renal panel, which is less than 25 dollars, to assure the animal is okay to take it. My 12 year old chow was fine until 10 days of treatment. It’s not the drug manufacturer’s fault. Your vet should warn you about this.

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