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Dr. Gene
Dr. Gene, Veterinarian
Category: Dog Veterinary
Satisfied Customers: 2662
Experience:  DVM degree from Ontario Veterinary College
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Can dogs take Bactrim DS If so, what dosage would be given

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Can dogs take Bactrim DS? If so, what dosage would be given to a 90lbs Mastiff with a severe ear infection & folliculitus?
Hi there,

While Bactrim DS can be used in dogs but I cannot legally provide dosing information as your dog is not my patient. Bactrim DS is an antibiotic that has probably the highest rate of adverse side effects in dogs, so it is used infrequently. Ear infections are difficult to treat sometimes, especially if they are chronic in nature. I would deal with this situation in the following manner if your dog was my patient (I'm sure some of this has been done):

1. Examination of the ear canals and ear drums with an otoscope (instrument with a light source).
2. Sample collected for microscopic examination; if certain types of bacteria are present, bacterial culture should be done so that the exact type of bacteria could be determined and effective antibiotics can be prescribed.
3. If the examination is not possible due to accumulation of debris and/or inflammation, swelling or pain, then a course of antiinflammatory medication is prescribed to reduce pain and inflammation and to open up the ear canals to examination.
4. If this does not happen after 1-2 week period, further examination and ear canal flushing under anesthesia should be done so that the health of the ear drum and middle ear canal could be determine and all debris removed. Without removal of debris and a clear ear canal, control of ear infection is not possible.
5. At this point, treatment is done based on culture or microscopic examination results. Topical medication (ointments) should be used only when the ear drum is intact and there is little to no debris in the canals. Otherwise, risk of either ineffectiveness of treatment (if debris present) or deafness (if ear drum ruptured) exists.

Ear infections should be treated aggressively with frequent follow up and rechecks. The cost of monitoring and treatment can understandably be large, however, the cost of chronic and irreversible consequences to the ear canals and hearing can be even larger.

Hope this helps! Please let me know if you have any other questions; best of luck!
Customer: replied 6 years ago.

Okay, so I will take him to get cultured.

What should I expect his vet to prescibe? His ears are immaculate, no debris. We tried topical ointments. I'm sure he will be given oral antibiotics. So I should not expect him to be prescribed Bactrim, right? So, no to that! What should I expect?


I am not surprised at all about Bactrim being tough for dogs to handle. This medication has given my daughter terrible side effects. It's a rough one.


Thank you for giving me another opinion, Doctor!

If the ears are clean on the outside as well as on the inside (ear canals in dogs are "L" shaped) and the ear drum is intact, assuming your vet still thinks there is an infection (less likely if no debris at all), then a topical medication can be prescribed based on cytology (microscopic examination for yeast or bacteria) - no culture necessary and the ears should get better soon. Culture is necessary in chronic cases, those unresponsive to antibiotics and when rod bacteria are seen on cytology.

So... if ears are clean all the way through you can/should expect ointment. If there is debris deeper inside (where you can't see) then oral medication is usually given, because ointments won't work if there is a lot of debris. Cleaning of the ear canals (if no pain or severe inflammation) should be done if there is debris. Cleaning should be done this way: instill cleaning solution into the ear canal until it's overflowing, hold up the ear flap and massage ear canal to loosen debris on the inside for 1 minute; let him walk around and shake his head, which will bring loosened debris to the surface, where you simply wipe away with cotton balls...

Good luck with your big guy!
Dr. Gene, Veterinarian
Category: Dog Veterinary
Satisfied Customers: 2662
Experience: DVM degree from Ontario Veterinary College
Dr. Gene and 4 other Dog Veterinary Specialists are ready to help you
Customer: replied 6 years ago.

Dr. Gene,


THANK YOU SO MUCH! I will take your advice and bring my pup to the vet! I am so happy I tried JustAnswer.... I really truely thought it was too good to be true, but your answer far exceeded my expectations. Now that I know what to look for and can be prepared, I feel more adept in spending my dwindling dollars. I very much appretiate it. Thank you.



You're very welcome. Take care! Thanks for the bonus!

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