About Sulfamethoxazole and Trimethoprim for Pets

Sometimes Called Trimeth Sulfa for Dogs and Cats, this Medication Treats Bacterial Infections

By Team PetCareRx.

  • URI (Upper Respiratory Infection)
  • Pyoderma (Skin Infection)
  • Urinary Tract Infection

Sulfamethoxazole and Trimethoprim


indications for Sulfamethoxazole and Trimethoprim

Trimethoprim is a potential sulfa drug with antibacterial properties, which is used in the treatment of many bacterial infections in dogs and cats. It is commonly used against the infections of the lungs, urinary tract, skin and gastrointestinal organs. Trimethoprim is found to be of use in treating conditions like Pneumonia, Enteritis, Otitis media, Prostatitis, Coccidiosis, Kennel cough, and Staphylococcal skin infections among others. The mechanism of Trimethoprim is to hinder the production of tetrahydrofolic acid from dihydrofolic acid by binding to it. Concurrently it also prevents the bacterial production of dihydrofolic acid, thereby offering a dual advantage.


Never use this medication in animals that are allergic to sulfonamides or in those with known liver or kidney ailments or blood related disorders. It is not safe to use this drug in pregnant and lactating animals. Disclose the complete medication history of the pet to the veterinarian before starting the therapy, as Trimethoprim can adversely interact with certain medicines like methotrexate, phenylbutazone, salicylates, anticoagulants, etc. The animals should have access to clean drinking water at all times, while undergoing Trimethoprim therapy.


Trimethoprim is a prescription drug and should never be used without consulting a licensed veterinarian. It is presented as tablets of 80/400mg and 160/800mg, and suspension of 40/200mg. The recommended daily dose in dogs and cats is 25 to 100 mg/kg given orally, (in two equal doses 12 hours apart) for 1-2 weeks. The medicine can also be given subcutaneously, intramuscularly or intravenously. Take care to complete the course unless specifically directed by the vet as chances of relapse is high.

Brand/Generic equivalents

Bactrim (Roche), Septra DS (Monarch), Tribrissen, (Schering-Plough), Di-Biotic (Phoenix Pharmaceutical), Albon (Pfizer Animal Health), Uniprim Powder (Macleod), Tucoprim Powder (Pharmacia & Upjohn), Borgal (Hoechst)

Side Effects

Some of the commonly reported side effects of Trimethoprim include loss of appetite, nausea, diarrhea, fever, anemia, allergic inflammations, hives, dry eyes and seizures.

Sulfamethoxazole and Trimethoprim


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Sulfamethoxazole and Trimethoprim at a glance

  • 1For dogs and cats
  • 2An antibacterial medication
  • 3An oral medication
  • 4Treats lung, skin, UTI, and gastrointestinal infections, pneumonia, enteritis, otitis media, and kennel cough

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