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Sulfasalazine

Prescription

Aminosalicylate Anti-inflammatory

Last reviewed 21 Apr 2026 · PetCare.AI Editorial Team

Species

Dog, Cat

Brands

1 available

Interactions

2 documented

Formulations

Mechanism of action

Prodrug cleaved by colonic bacteria into 5-aminosalicylic acid (5-ASA, the active anti-inflammatory moiety) and sulfapyridine (absorbed systemically). 5-ASA acts locally on colonic mucosa, inhibiting prostaglandin synthesis, leukotriene B4 production, and NF-κB activation.

At a glance

Class

Aminosalicylate Anti-inflammatory

Schedule

Prescription

Storage

Store at room temperature, protect from light and moisture

Dosing

🐕

Dog

First-line for colitis (lymphocytic-plasmacytic colitis, histiocytic ulcerative

Dose

20–50 mg/kg

Route

Frequency

q8–12h

🐈

Cat

Cats are very sensitive to salicylate toxicity (slow acetylation)

Dose

10–20 mg/kg

Route

Frequency

q12h

Formulations

💊

Other — 3

Strength

—

Strength

—

Strength

—

Storage

Store at room temperature, protect from light and moisture

Safety

Monitoring parameters

Schirmer tear test baseline and monthly (KCS)Hepatic enzymesCBC (hemolytic anemia)Clinical colitis response at 2–4 weeks

Interactions

Moderate — 2

Digoxin

moderate

Sulfasalazine may reduce digoxin absorption from the GI tract.

Management: Separate administration by 2 hours. Monitor digoxin levels.

Folic Acid

moderate

Sulfasalazine inhibits folate absorption (sulfapyridine component inhibits dihydrofolate reductase). Chronic use causes folate deficiency.

Management: Supplement with folic acid 0.5-1 mg/day during chronic sulfasalazine therapy.

Brands

Other markets

Azulfidine

FAQs

Frequently asked questions

›What is Sulfasalazine?

Sulfasalazine is a aminosalicylate anti-inflammatory used in pets. Prodrug cleaved by colonic bacteria into 5-aminosalicylic acid (5-ASA, the active anti-inflammatory moiety) and sulfapyridine (absorbed systemically). 5-ASA acts locally on colonic mucosa, inhibiting prostaglandin synthesis, leukotriene B4 production, and NF-κB activation.

›What is Sulfasalazine used for in pets?

Sulfasalazine is used in veterinary medicine for: First-line for colitis (lymphocytic-plasmacytic colitis, histiocytic ulcerative ; Cats are very sensitive to salicylate toxicity (slow acetylation).

›What is the Sulfasalazine dose for dogs?

For dogs, Sulfasalazine is typically dosed as follows — First-line for colitis (lymphocytic-plasmacytic colitis, histiocytic ulcerative : 20–50 mg/kg PO q8–12h. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›What is the Sulfasalazine dose for cats?

For cats, Sulfasalazine is typically dosed as follows — Cats are very sensitive to salicylate toxicity (slow acetylation): 10–20 mg/kg PO q12h. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›Does Sulfasalazine need a prescription?

Yes. Sulfasalazine is a prescription medication and should only be administered under veterinary supervision.

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. Find a vet near you →