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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

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 →

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

Educational reference only

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.

Educational reference only

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.

Educational reference only

References

The PetCare.AI drug reference is built from 13 authoritative sources cited across 580 drug monographs.

Textbooks & handbooks — 5

Plumb's Veterinary Drug Handbook
Withrow & MacEwen's Small Animal Clinical Oncology
Merck Veterinary Manual
NRC Nutrient Requirements of Dogs and Cats
Veterinary Pharmacology and Therapeutics (Riviere & Papich)

Clinical guidelines & consensus — 4

ASPCA Animal Poison Control Center Guidelines
AAHA Diabetes Management Guidelines
ASPCA Poison Control Guidelines
RECOVER CPR Guidelines

Journals & peer-reviewed studies — 2

EPIC Study (J Vet Intern Med 2016)
JVIM FAT CAT Study

Regulatory & approvals — 1

CDSCO Veterinary Drug Approval Registry (1969–2026)

Databases — 1

Washington State University VCPL MDR1 Database