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October 12, 2023

Sulfa drug sensitivity in dogs often makes us think about Doberman Pinschers, but they are not the only breed potentially affected by sulfonamide medications. Let's look at theories on causes and common symptoms. 

sulfa drug sensitivity in dogs causes and symptoms

What Causes Sulfa Drug Sensitivity in Dogs?

One study found an association with a mutation in the CYB5R3 gene and sulfonamide hypersensitivity in dogs. That gene encodes an enzyme that helps metabolize drugs. However, weirdly enough, it is NOT involved with how sulfa drugs get processed. So, the working theory now is that there may be more than one gene mutation (polymorphism) involved. 

What Dog Breeds Most at Risk for Sulfa Drug Reactions?

However, the CYB5R3 gene mutation in dogs *is overrepresented in breeds that develop sulfonamide drug reactions, including:

  • Doberman Pinschers (as high as 21% mortality rate due to sulfa drug reactions) ... but that study only included 6 dogs.
  • Samoyeds
  • Miniature Schnauzers
sulfa drug sensitivity in dogs photo of doberman jumping in dock diving

Meet CH Aludra’s Magic Flute CA BCAT CGC TKN NW1 “Marley” who lives with my pal Lisa Miller in GA. Lisa and I met when her prior doberman (Maddie) suffered the same type of adverse vaccine reaction as our original canine heroine, Lilly.

What are Sulfa Drugs?

Pretty much various types of antibiotics. Typically older ones with risks of overuse that can lead to drug-resistant bacteria. Yikes!

Sulfa drug names in veterinary medicine include Sulfamethazine (SMZ), Trimethoprim, and Bactrim. They're typically used for gastrointestinal or respiratory infections. 

What are the Common Symptoms of Sulfa Drug Sensitivity in Dogs?

Dogs with hypersensitivity to sulfa drugs can experience symptoms like these:

  • Rash of itchy big round welts on the skin
  • Skin swelling
  • Dryness and redness of the eyes
  • Fever 
  • Widespread joint pain
  • Dangerously low red blood cell counts (hemolytic anemia)
  • Dangerously low neutrophil counts (a specific kind of white blood cell)
  • Anaphylaxis (acute allergic reaction, life-threatening)

What to Do If Your Dog Suffers a Sulfa Drug Reaction?

Your best action is to seek emergency veterinary care ASAP.

About the Author Roxanne Hawn

Trained as a traditional journalist and based in the Rocky Mountains of Colorado, USA, I'm a full-time freelance writer for magazines, websites, and private clients. My areas of specialty include everything in the lifestyles arena, including health and home, personal finance and other consumer interests, relationships and trends, people and business profiles ... and, of course, all things pet related.

I don't just love dogs. I need them in my life. Seriously.

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