Sulfasalazine

What is sulfasalazine?

Sulfasalazine (brand names: Azulfidine®, Sulfazine®, Salazopyrin®) is a sulfonamide antibacterial and immunosuppressive medication used off label (extra label) to treat inflammatory large bowel disease and vasculitis in cats, dogs, ferrets, and horses.

Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. 

In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How is sulfasalazine given?

• Sulfasalazine is given by mouth in the form of a tablet.
• Give this medication with food.
• Handle this medication with caution if you have a known allergy to sulfa drugs; wearing gloves is recommended and be sure to wash your hands after administering.

This medication should take effect within 1 to 2 hours. Effects may not be immediately visible, but gradual improvements are usually noticeable after a few days.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.

Are there any potential side effects?

Sulfasalazine may cause the following side effects:

• Decreased appetite
• Vomiting
• Yellowing of the skin, eyes, or body fluids
• Anemia (in cats)

Serious adverse reactions may occur. If any of the following signs develop, stop giving sulfasalazine and contact your veterinarian immediately:

• Dry eye/keratoconjunctivitis sicca (KCS) (will appear as squinting, mucoid eye discharge, and eye discomfort)
• Lack of energy
• Persistent vomiting
• Diarrhea
• Lack of appetite
• Paleness
• Fever
• Skin rashes

Drug sensitivities can develop over time, with repeated exposure. Your pet may have no reaction after the first few doses but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment (e.g., irregular breathing, rash, fever, puffiness and swelling around the face) and notify your veterinarian if you have any concerns.  

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately.  This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

DO NOT USE sulfasalazine in:

• Pets that are allergic to it or other sulfonamides or salicylates
• Doberman pinschers, miniature schnauzers, or samoyeds
• Pets with dry eye/KCS
• Pets with intestinal or urinary blockages
• Pets with severe dehydration

USE WITH CAUTION in:

• Cats
• Pets with liver, kidney, or blood diseases
• Pets that are pregnant or nursing
• Sensitive dog breeds, such as cocker spaniels, bulldogs, West Highland terriers, Lhasa apsos, or shih tzus

Are there any drug interactions I should be aware of?

Several medications should be used with caution when given with sulfasalazine, including:

• Antibacterial agents
• Cyclosporine
• Ferrous sulfate and other iron salts
• Folic acid

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any treatment.

Is any monitoring needed with this medication?

• Your veterinarian will let you know when and how they want to reassess your pet to ensure the medication is working and not causing side effects.
• Your veterinarian may monitor for KCS/ dry eye, by performing a tear test before starting therapy and rechecking regularly during therapy.
• For long-term therapy, your veterinarian may regularly monitor blood cell counts and liver panels.
• At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian.

How do I store sulfasalazine?

• Store the tablets at room temperature, between 68°F and 77°F (20°C and 25°C); do not exceed 104°F (40°C).
• Protect from light.
• Keep the container out of reach of children and pets.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet's weight and symptoms.