Sequential blockade of folate synthesis: sulfadiazine inhibits dihydropteroate synthase and trimethoprim inhibits dihydrofolate reductase, producing synergistic bactericidal activity
At a glance
Class
Sulfonamide + Diaminopyrimidine antibiotic combination
Storage
Store below 25°C, protect from light
Dosing
Susceptible bacterial infections (UTI, skin, respiratory)
Max dose
1500 mg/dose; 3000 mg/day
Duration: 7–14 days; avoid >14 days continuous
Susceptible bacterial infections
Max dose
400 mg/dose; 800 mg/day
Duration: 7–14 days
Safety
Absolute contraindications — do not use
Hepatic insufficiency
Dobermans may be predisposed to sulfonamide hypersensitivity
Keratoconjunctivitis sicca risk
Prolonged use may cause KCS
Adverse effects
Common
Inappetence
Vomiting
Diarrhoea
Serious
KCS (dry eye)
Hepatotoxicity
Blood dyscrasias
Sulfonamide crystalluria
Schirmer tear test (prolonged use)CBCUrinalysis
Interactions
No documented interactions.
Brands
India
Sulphatrim-Vet
TTK Healthcare
FAQs
Frequently asked questions
›What is Sulfadiazine + Trimethoprim?
Sulfadiazine + Trimethoprim is a sulfonamide + diaminopyrimidine antibiotic combination used in pets. Sequential blockade of folate synthesis: sulfadiazine inhibits dihydropteroate synthase and trimethoprim inhibits dihydrofolate reductase, producing synergistic bactericidal activity
›What is Sulfadiazine + Trimethoprim used for in pets?
Sulfadiazine + Trimethoprim is used in veterinary medicine for: Susceptible bacterial infections (UTI, skin, respiratory); Susceptible bacterial infections.
›What is the Sulfadiazine + Trimethoprim dose for dogs?
For dogs, Sulfadiazine + Trimethoprim is typically dosed as follows — Susceptible bacterial infections (UTI, skin, respiratory): 15–30 mg/kg PO BID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What is the Sulfadiazine + Trimethoprim dose for cats?
For cats, Sulfadiazine + Trimethoprim is typically dosed as follows — Susceptible bacterial infections: 15–30 mg/kg PO BID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What are the side effects of Sulfadiazine + Trimethoprim?
Common: Inappetence, Vomiting, Diarrhoea. Serious (call your vet immediately): KCS (dry eye), Hepatotoxicity, Blood dyscrasias, Sulfonamide crystalluria.
›Does Sulfadiazine + Trimethoprim need a prescription?
Yes. Sulfadiazine + Trimethoprim is a prescription medication and should only be administered under veterinary supervision.
›When should Sulfadiazine + Trimethoprim not be used?
Do not use Sulfadiazine + Trimethoprim if: Sulfonamide hypersensitivity.
References
References
Textbooks & handbooks
- Plumb, D.C. Plumb's Veterinary Drug Handbook. 10th ed., Wiley-Blackwell, 2023.
- Vail, D.M., Thamm, D.H., & Liptak, J.M. (eds.). Withrow & MacEwen's Small Animal Clinical Oncology. 6th ed., Saunders/Elsevier, 2020.
- Riviere, J.E., & Papich, M.G. (eds.). Veterinary Pharmacology and Therapeutics. 10th ed., Wiley-Blackwell, 2018.
- National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press, Washington DC, 2006.
- The Merck Veterinary Manual. Merck & Co., Online edition. https://www.merckvetmanual.com/
Clinical guidelines & consensus
- Fletcher, D.J., Boller, M., Brainard, B.M., et al. "RECOVER Evidence and Knowledge Gap Analysis on Veterinary CPR." Journal of Veterinary Emergency and Critical Care, 2012;22(S1):S102–S131.
- American Animal Hospital Association. 2018 AAHA Diabetes Management Guidelines for Dogs and Cats. AAHA Press.
Journals & peer-reviewed studies
- Hogan, D.F., Fox, P.R., Jacob, K., et al. "Secondary prevention of cardiogenic arterial thromboembolism in the cat: The FAT CAT study." Journal of Veterinary Cardiology, 2015;17(Suppl 1):S306–S317.
- Boswood, A., Häggström, J., Gordon, S.G., et al. "Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study — A Randomized Clinical Trial." Journal of Veterinary Internal Medicine, 2016;30(6):1765–1779.
- ASPCA Animal Poison Control Center. Toxicology and Poison Management Guidelines. American Society for the Prevention of Cruelty to Animals. https://www.aspca.org/pet-care/animal-poison-control
Regulatory & approvals
- Central Drugs Standard Control Organisation (CDSCO), Government of India. Veterinary Drug Approval Registry, 1969–2026. Directorate General of Health Services. https://cdsco.gov.in/
Databases
- Washington State University, College of Veterinary Medicine. Veterinary Clinical Pharmacology Laboratory (VCPL) — MDR1 Multidrug Sensitivity Database. https://vcpl.vetmed.wsu.edu/
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet.
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