Sulfadiazine-induced allergy in six Doberman pinschers.

Treatment with sulfadiazine-trimethoprim caused serious, but reversible, allergic drug reactions in 6 Doberman Pinschers 10 to 21 days after the first drug exposure and/or within 1 hour to 10 days after reexposure. Nonseptic polyarthritis was found in all dogs. Glomerulonephropathy, focal retinitis, polymyositis, skin rash, fever, anemia, leukopenia, and thrombocytopenia were found in some dogs. These clinical abnormalities were typical of an immune-mediated vasculitis and mimicked other immune-mediated disorders. In a drug challenge study, 1 dog was given sulfadiazine and trimethoprim separately. Administration of trimethoprim alone did not result in any abnormalities; however, exposure to sulfadiazine caused recurrence of the polyarthritis, glomerulonephropathy, and focal retinitis within 5 days, suggesting that sulfadiazine likely was the offending agent in all cases. In addition, during the sulfadiazine reexposure, marked complement activation was documented at the time clinical signs were apparent, supporting the suggestion that sulfadiazine caused an immune complex disease (type-III hypersensitivity reaction). Since all dogs were of the same breed, a genetic predisposition of some Doberman Pinschers to react adversely to sulfadiazine was suspected.