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Effect of trimethoprim/sulfamethoxazole on thyroid function in dogs with pyoderma
I A Hall1, K L Campbell, M D Chambers
1Department of Veterinary Clinical Medicine, University of Illinois, Urbana 61801.
Journal of the American Veterinary Medical Association
|June 15, 1993
Summary
Trimethoprim/sulfamethoxazole (T/SMX) treatment in dogs can decrease thyroxine levels and impair thyroid function. This may lead to misdiagnosis of hypothyroidism in dogs receiving this common antibiotic.
Area of Science:
- Veterinary Medicine
- Endocrinology
- Pharmacology
Background:
- Pyoderma is a common skin infection in dogs.
- Thyroid dysfunction can affect canine health.
- Trimethoprim/sulfamethoxazole (T/SMX) is a widely used antibiotic.
Purpose of the Study:
- To evaluate the impact of T/SMX on thyroid function in dogs with pyoderma.
- To determine if T/SMX affects serum thyroxine and triiodothyronine levels.
- To investigate potential mechanisms of T/SMX-induced thyroid changes.
Main Methods:
- 21 dogs with pyoderma received T/SMX (30 mg/kg, PO, q 12 h) for 6 weeks.
- Serum thyroxine and triiodothyronine concentrations were measured before and after treatment.
- Thyroid function was assessed via thyrotropin stimulation tests and radionuclide imaging.
Main Results:
- Mean serum thyroxine concentration significantly decreased post-treatment.
- Thyrotropin response was reduced in 3 dogs after T/SMX.
- Thyroid imaging showed increased technetium 99m pertechnetate uptake, suggesting iodide metabolism interference.
Conclusions:
- T/SMX administration can lead to decreased thyroid function in dogs.
- Hypothyroidism may be inadvertently induced or misdiagnosed in dogs treated with T/SMX.
- Clinicians should consider T/SMX's potential effects on thyroid function during diagnosis and treatment.