Trimethoprim-Sulfa

Updated on September 10, 2024

Potentiated sulfonamide antimicrobial agent used to treat many infections common in small animals.

Trimethoprim-Sulfa

Summary

Used For: Bacterial and protozoal infections

Brands: Tribrissen, Bactrim, Septra

Species:

Dogs, cats and other small animals

Other names: TMP-SMX, TMP-SDZ, Trimethoprim-sulfadiazine, trimethoprim-sulfamethoxazole

Drug type: Antibiotic

Prescription required: Yes

Pregnancy and lactation: Use with caution, safety has not been clearly established in pregnant or lactating animals.

Side effects: Dry eye, hypothyroidism, anaphylaxis, liver disease, blood effects

General description

Trimethoprim-sulfa is a potentiated sulfonamide antimicrobial used to treat certain bacterial and protozoal infections in veterinary medicine.

Uses

Bacterial urinary tract infections, skin infections, and other soft tissue infections; also used for protozoal infections.

How it works

The combination of trimethoprim with a sulfonamide gives this medication a broader spectrum of activity against susceptible microorganisms with less antibiotic resistance than either component alone. Potentiated sulfa drugs kill microorganisms by inhibiting enzymes, causing the bacteria to die.

Dosage

Dosages vary greatly based on species and infection being treated. Follow prescribing directions from your veterinarian. Medications should only be administered to pets under the direct guidance of a veterinarian.

Forms

25, 100, 400 or 800 milligrams sulfadiazine in combination with 5, 20, 80 or 160 milligrams trimethoprim tablets for oral use.

Storage information & handling

Trimethoprim-sulfa should be stored at room temperature.

What results can I expect?

Assuming the infection is susceptible to trimethoprim-sulfa, resolution of the infection should occur during the treatment period.

Missed Dosage

If a dose is missed, continue with the next dosage at the scheduled time.

Overdose / acute toxicity

Signs of an overdose include nausea, vomiting, diarrhea, depression, confusion and facial swelling. Call your veterinarian immediately if you suspect your pet has received an overdose of trimethoprim-sulfa.

Side effects

May include: * Dry eye (KCS, Keratoconjunctivitis sicca) * Acute neutrophilic hepatitis (liver disease) with jaundice, vomiting, diarrhea, fever, decreased appetite, facial swelling, increased thirst and urination, hives and polyarthritis * Hypothyroidism (dogs) * Anaphylaxis * Blood effects (anemia, decreased production of certain white blood cells) * Cats: decreased or absent appetite, blood effects (anemia, decreased white blood cells)

Contraindications

Do not use in pets with: * Hypersensitivity to sulfas, thiazides or sulfonylurea agents * Severe kidney disease * Severe liver disease

Drug interactions

Trimethoprim-sulfa may interact with: * Amantadine * Antacids * Cyclosporine * Digoxin * Thiazide diuretics * Oral hypoglycemic agents * Methotrexate * Phenytoin * Tricyclic antidepressants * Warfarin

Precaution

Trimethoprim-sulfa should be used with caution in patients with: * Decreased kidney function * Decreased liver function * Urinary obstructions or urolithiasis (stones in the urinary tract)

Sources

*Plumb’s Veterinary Drug Handbook*
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Disclaimer

The information contained on this page is for educational purposes only. This medication should only be given under the advice of a veterinarian who has examined your pet under the laws applicable to your state of residence.