Trimethoprim/Sulfadiazine or Sulfamethoxazole

(trye-meth-ohe-prim; sul-fa-dye-a-zeen or sul-fa-meth-ox-a-zole)
Category: Sulfonamide Antibiotic
Other Names for this Medication: TMS, Co-trimoxazole, Equisul-SDT®, Tucoprim®, Tribrissen®
Common Dosage Forms: Veterinary: Note: All are equine labeled products. Oral Suspension: Trimethoprim 67 mg/gram & Sulfadiazine 333mg/gram; Oral Powder: Trimethoprim 67 mg/gram & Sulfadiazine 333mg/gram; Injection: 48% in 100 ml vials;Oral Paste: Trimethoprim 67 mg/gram & Sulfadiazine 333mg/gram (may be unavailable in the USA). Human: Oral tablets: Single strength, Trimethoprim 80 mg & Sulfamethoxazole 400 mg; Double Strength, trimethoprim 160 mg & sulfamethoxazole 800 mg.

This information sheet does not contain all available information for this medication. It is to help answer commonly asked questions and help you give the medication safely and

effectively to your animal. If you have other questions or need more information about this medication, contact your veterinarian or pharmacist.

Key Information

X Antibiotic usually given twice a day in small animals. Horses usually get the oral paste once a day. Can be given with or without food.

X Allow free access to water; animal must not become dehydrated while getting this drug.

X Usually tolerated well but many side effects are possible, including severe diarrhea and allergic reactions.

X Because of the risk for dry eye while on this medication, your pet may have its tear production tested before starting this antibiotic. If your dog develops red eyes, has eye discharge, or squints its eyes, contact your veterinarian.

X If using oral suspension, shake well before using. This drug does not need to be refrigerated.

X Complete the entire course of antibiotics prescribed by your veterinarian even if your animal appears well.

How is this medication useful?

Trimethoprim with a sulfonamide is an antibiotic used to treat bacterial infections in animals. This drug is also used to treat some types of parasitic infections in small animals.

The FDA (U.S. Food & Drug Administration) has approved some drugs containing trimethoprim with sulfadiazine for use in animals, but often human-approved products containing trimethoprim with sulfamethaxazole are used in dogs and cats. The FDA does allow veterinarians to prescribe and use human products in certain situ- ations. You and your veterinarian can discuss why this drug is the most appropriate choice.

What should I tell my veterinarian to see if this medication can be safely given?

Many things might affect how well this antibiotic will work in your animal. Be sure to discuss the following with your veterinarian so together you can make the best treatment decisions.

XXOther drugs can interact with this drug, so be sure to tell your veterinarian and pharmacist what medications (including vitamins, supplements, or herbal therapies) you give your animal, including the amount and time you give each.

XXTell your veterinarian about any conditions or diseases your animal may have now or has had in the past.

XXTell your veterinarian and pharmacist about any medication side effects (including allergic reactions, lack of appetite, diarrhea, itching, hair loss) your animal has developed in the past.

When should this medication not be used or be used very carefully?

No drug is 100% safe in all patients, but your veterinarian will discuss with you any specific concerns about using this drug in your animal.

This drug SHOULD NOT be used in patients:
XXThat are allergic to either drug or other similar drugs (eg,

sulfadimethoxine, ormetoprim).
XXThat have severe liver disease or blood problems.XXThat are dehydrated.
This drug should be used WITH CAUTION in:

XXDoberman pinschers appear to be very susceptible to a serious immune-related condition (poly-systemic immune complex disease) that can be caused by sulfa drugs; many veterinarians will avoid using this drug combination in this breed.

XXAnimals that have liver, kidney, or thyroid disease.
XXAnimals with or that have a history of kidney or bladder stones as

they can be at higher risk for new stones with this drug.XXAnimals that are old, severely sick, or debilitated (weakened, frail).

If your animal has any of these conditions or signs, talk to your veterinarian about the potential risks versus benefits.

What are the side effects of this medication?

Common, but usually not serious side effects include:

XXDogs: Reduced appetite, vomiting, loose stools (diarrhea).XXCats: Reduced appetite, increased salivation after giving a dose.XXHorses: Mildly loose stools.

You don’t have to be overly concerned if you see any of these unless they are persistent or worsen. Contact your veterinarian if this happens.

Side effects that may be serious or indicate a serious problem:


XXDry eye syndrome (keratoconjunctivitis sicca; KCS). Before your dog takes this drug, your veterinarian will want to test your dog’s tear production. Signs of dry eye include redness or discharge from the eyes or increased blinking.

XXDifficulty or straining to urinate, blood in urine.
XXSkin conditions: Sores, skin that appears to be burned, severe

itching, loss of fur.
XXIncreased thirst and urination.
XXSwelling of face.
XXLack of energy or appetite, tiredness, fever.

XXIf your animal has been treated for the same disease or condition in the past, tell your veterinarian about the treatment and how well it did or didn’t work.

XXIf your animal is pregnant or nursing, talk to your veterinarian about the risks of using this drug.

©2017 PharmaVet, Inc. ALL RIGHTS RESERVED. Plumb’s® Veterinary Medication Guides have not been reviewed by FDA Center for Veterinary Medicine.

XXDifficulty walking.

XXYellowing of the gums or whites of eyes (jaundice).


XXLack of appetite, refusal to eat.

XXDifficulty or straining to urinate, blood in urine.

XXLack of energy, tiredness.



XXSevere diarrhea



XXDry eye syndrome (see above information for dogs).

If your animal develops any of these signs, contact your veterinar- ian immediately.

If my animal gets too much of this medication (an overdose), what should I do?

this medication, talk to your veterinarian, as there may be important reasons to continue its use.

What should I do if I miss giving a dose of this medication?

Unless it is within 6 hours of the next scheduled dose, give the medication when you remember and give the next dose at its reg- ular time. If it is within 6 hours of the next scheduled dose, give the medication, and skip that next dose and then begin giving it at the regular scheduled times.

How should I store this medication?

Store tablets, oral paste, and suspension at room temperature. Store in the original prescription bottle, oral syringe, or an ap- proved dosage reminder (ie, pill minder) container; protect tablets from moisture. Store liquid forms of this medication in the refriger- ator.

XXIf your veterinarian or pharmacist has made (compounded) a special formulation for your animal, follow the storage recommendations and expiration date for the product.

XXKeep away from children and other animals.
Can handling this medication be hazardous to me, my family, or

other pets?

Humans with severe allergies to sulfa compounds should avoid handling it or wear disposable gloves when giving it; wash hands after handling any medication.

How should I dispose of this medication if I don’t use it all?

XXDo not flush this medication down the toilet or wash it down the sink. If a community drug “take-back” program is available, use this option. If there is no take-back program, mix the drug with coffee grounds or cat litter (to make it undesirable to children and animals and unrecognizable to people who might go through your trash), place the mixture in a sealable plastic bag to keep it from leaking out, and throw the bag out with the regular trash.

XXDo not save left over medication for future use or give it to others to use.

What other information is important for this medication?

XXYour veterinarian may wish to monitor your pet by doing intermittent tests to measure tear production, blood cells, and thyroid function while your animal is receiving this medication.

XXUse of this drug may not be allowed in certain animal competitions. Check rules and regulations before entering your animal in a competition while this medication is being administered.

If you have any other questions or concerns about this medica- tion, contact your veterinarian or pharmacist.

If you witness or suspect an overdose, contact your veterinarian or an animal poison control center for further advice. Animal poison control centers that are open 24 hours a day include: Pet Poison HELPLINE (855-764-7661) and ASPCA Animal Poison Control Cen- ter (888-426-4435); a consultation fee is charged for these services.

How should this medication be given?

For this medication to work, give it exactly as your veterinarian has prescribed. It’s a good idea to always check the prescription label to be sure you are giving the drug correctly.
XXMay be given with or without food. If your pet vomits or acts sick

after receiving the drug on an empty stomach, try giving the next dose with food or a small treat. If vomiting continues, contact your veterinarian.

XXCats do not like the taste of this drug and will salivate (drool, foam) profusely if allowed to taste it. Putting the drug inside capsules to avoid direct contact with the tongue can make giving the medication easier.

XXOral paste should be placed far back on the tongue of horses.

XXIf you have difficulty getting your animal to take the medicine, contact your veterinarian or pharmacist for tips to help dosing and reducing the stress of medication time.

XXLiquid forms of this medication should be shaken well before giving and must be measured carefully. Your veterinarian or pharmacist can help by providing special measuring spoons or syringes.

XXThis medication can be given for various lengths of time. Be sure you understand how long your veterinarian wants you
to continue giving this medication. Prescription refills may be necessary before the therapy will be complete. Before stopping

©2017 PharmaVet, Inc. ALL RIGHTS RESERVED. Plumb’s® Veterinary Medication Guides have not been reviewed by FDA Center for Veterinary Medicine.