Sulfasalazine

What is this medication for?

• Inflammatory large-bowel disease (colitis); adjunct for vasculitis
• Colitis — cautious use (salicylate sensitivity)

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• Schirmer tear testing on schedule is the monitoring hallmark — dry eye can be irreversible if missed.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Sulfonamide hypersensitivity (Type I/III) (Large-breed dogs predisposed; Dobermans especially — many consider sulfonamides contraindicated in them)

Worth a phone call to your veterinarian

• Anorexia, vomiting, cholestatic jaundice, hemolytic low red blood cell counts, low white blood cell counts, allergic dermatitis, ↓ sperm counts (Uncommon)

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Keratoconjunctivitis sicca (dry eye/dry eye) (Most frequent canine effect — may be irreversible; early detection allows reversal)

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Sulfonamide/salicylate hypersensitivity; intestinal or urinary obstruction; Doberman pinschers (idiosyncratic polysystemic immune-complex disease)
• has or has had: Preexisting liver/renal/hematologic disease; cats — salicylate sensitivity (see aspirin), keep courses ≤10 days

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Digoxin
  • Ferrous sulfate/iron salts
  • Folic acid
  • Warfarin
  • Chlorpropamide

Storage and handling

Room temperature, light-resistant. Enteric-coated tablets preferred in cats.

Good to know

• Colonic bacteria are required to activate it — useless for small-intestinal inflammation. The pro-drug design delivers high local 5-ASA to the colon while sparing systemic salicylate exposure.
• Schirmer tear testing on schedule is the monitoring hallmark — dry eye can be irreversible if missed.
• Cats: once daily, short course, salicylate caution (same glucuronidation deficit as aspirin).
• Overdose = combined salicylate + sulfonamide toxicity → urine alkalinization helps.