Gastrointestinal · Drug monograph

Sulfasalazine: veterinary dose and monograph

Sulfasalazine is a veterinary gastrointestinal drug. Sulfapyridine–5-aminosalicylic acid prodrug split by colonic bacteria; the 5-ASA acts locally in the colon. Indications include chronic colitis / large-bowel IBD (dogs, cats, ferrets); cutaneous vasculitis (dogs). This monograph lists 4 reference doses for dogs, cats and ferrets, each with route, frequency and source.

At a glance

Drug class: Gastrointestinal
Also known as: Salazopyrin, Azulfidine, Sulphasalazine
Species with doses: Dogs, Cats and Ferrets
General dose range: 10–30 mg/kg PO q8–12h — check the species tables for the indication
Routes: PO
Last reviewed: 1 October 2026

Indications

Chronic colitis / large-bowel IBD (dogs, cats, ferrets)
Cutaneous vasculitis (dogs)

Sulfasalazine dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

Sulfasalazine doses for dogs
Indication	Dose	Route	Frequency	Duration
Colitis / large-bowel IBD	10–30 mg/kg	PO	q8–12h, then taper	—
Cutaneous vasculitis (adjunct)	20–40 mg/kg	PO	q8h	—

Colitis / large-bowel IBD: Papich 5e: 10–30 mg/kg q8–12h PO. Plumb’s p.1095: 20–40 mg/kg q8h for 3 weeks, then q12h for 3 weeks, then 10–20 mg/kg q12h for 3 weeks (Marks); 20–50 mg/kg (max 1 g per dose) q8h, usually starting at 20–30 mg/kg, tapering at 2–4-week intervals (Leib); 10–25 mg/kg q8h for 4–6 weeks (Washabau). Check Schirmer tear tests before and during treatment.
Cutaneous vasculitis (adjunct): Plumb’s p.1095: 20–40 mg/kg PO q8h (Hillier; Griffin); 25 mg/kg three times daily (Bloom). Monitor tear production and CBC.

Cats

Sulfasalazine doses for cats
Indication	Dose	Route	Frequency	Duration
Colitis (short course, caution)	10–20 mg/kg	PO	q12–24h	maximum 10 days

Colitis (short course, caution): Plumb’s p.1095: 10–20 mg/kg PO once daily, tapered (Jergens & Willard; Moore; Marks); 10–20 mg/kg q8–24h for no more than 10 days (Dimski; Krecic). Papich 5e: 20 mg/kg q12h PO. Cats are sensitive to salicylates.

Ferrets

Sulfasalazine doses for ferrets
Indication	Dose	Route	Frequency	Duration
Colitis	10–20 mg/kg	PO	q8–12h	—

Colitis: Plumb’s p.1095: 10–20 mg/kg PO two to three times daily (Williams); 25 mg per ferret twice daily (Weiss).

Contraindications

Sulfonamide or salicylate hypersensitivity; pre-existing KCS; hepatic disease or blood dyscrasias. Cats are salicylate-sensitive — short courses at low doses only.

Adverse effects

Keratoconjunctivitis sicca (dogs)
Vomiting, anorexia
Cholestatic jaundice, haemolytic anaemia, leukopenia (rare)
Allergic dermatitis

Monitoring

Schirmer tear test before and periodically during treatment
CBC and liver values on long courses

Formulations and products

500 mg tablet (plain or enteric-coated)

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Frequently asked questions

What is the dose of Sulfasalazine for dogs?

Reference doses for Sulfasalazine in dogs: 10–30 mg/kg PO q8–12h, then taper (Colitis / large-bowel IBD); 20–40 mg/kg PO q8h (Cutaneous vasculitis (adjunct)). Confirm against the label and the patient before use.

What is the dose of Sulfasalazine for cats?

Reference doses for Sulfasalazine in cats: 10–20 mg/kg PO q12–24h for maximum 10 days (Colitis (short course, caution)). Confirm against the label and the patient before use.

What is the dose of Sulfasalazine for ferrets?

Reference doses for Sulfasalazine in ferrets: 10–20 mg/kg PO q8–12h (Colitis). Confirm against the label and the patient before use.

When should Sulfasalazine not be used?