Aplastic anemia associated with prolonged high-dose trimethoprim-sulfadiazine administration in two dogs

Trimethoprim-sulfadiazine (TMP-SDZ) (Tribressin tablets 120 - 100 mg sulfadiazine, 20-mg trimethoprim [Coopers Animal Health, Inc., A Pitman-Moore Company, Mundelein, Ill.]) is a broad spectrum antibiotic combination effective in the treatment of bacterial pneumonia, urinary tract infections, pyoderma, meningitis, and prostatitis.(1) In clinical trials in puppies and adult dogs, TMP-SDZ was considered safe at both the manufacturer's recommended dose (15 mg/kg, b.i.d., or 30 mg/kg, u.i.d., per os for < 14 days(2)) and at 10 times that dose for 20 dayS.(3) Many infections, however, require prolonged high-dose therapy for resolution. The following study describes two cases of aplastic anemia and sepsis associated with intermittent, chronic (17-25 days), high-dose (25-30 mg/kg, b.i.d., per os) TMP-SDZ therapy recommended for the treatment of pyoderma.(4-7)