Journal article
Effects of long-term phenobarbital treatment on the thyroid and adrenal axis and adrenal function tests in dogs
Journal of veterinary internal medicine, Vol.14(2), pp.157-164
Revised March 12, 1999, and July 1, 1999; Accepted October 19, 1999
2000
PMID: 10772487
Abstract
Phenobarbital can interfere with the thyroid axis in human beings and rats by accelerating hepatic thyroxine metabolism because of enzyme induction. In human beings, it also can interfere with the low-dose dexamethasone suppression test (LDDST) used to assess adrenal function by accelerating dexamethasone metabolism. This effect can cause a lack of suppression of pituitary ACTH and subsequent adrenal cortisol release after dexamethasone administration. The effects of phenobarbital on the thyroid axis, the adrenal axis, and adrenal function tests were prospectively investigated in 12 normal, adult dogs. Phenobarbital was administered at 5 mg per kilogram of body weight (range, 4.8–6.6 mg/kg) PO q12h for 29 weeks, resulting in therapeutic serum concentrations (20–40 μg/mL). Serum total thyroxine (TT4), free thyroxine (FT4) by equilibrium dialysis, total triiodothyronine (TT3), thyrotropin (TSH), and cholesterol were determined before and during phenobarbital treatment. LDDST, ACTH stimulation tests, and ultra-sonographic evaluation of the adrenal glands were performed before and during treatment. TT4 and FT4 decreased significantly (P≤ .05), TT3 had minimal fluctuation, TSH had only a delayed compensatory increase, and cholesterol increased during phenobarbital treatment. The delayed increase in TSH, despite persistent hypothyroxinemia, suggests that accelerated hepatic thyroxine elimination may not be the only effect of phenobarbital on the thyroid axis. There was no significant effect of phenobarbital on either of the adrenal function tests. With the methods employed, we did not find any effects of the drug on the hormonal equilibrium of the adrenal axis.
Details
- Title
- Effects of long-term phenobarbital treatment on the thyroid and adrenal axis and adrenal function tests in dogs
- Authors/Creators
- Peter B. Müller - Department of Veterinary Physiology, Pharmacology and ToxicologyKaren J. Wolfsheimer - Department of Veterinary Physiology, Pharmacology and ToxicologyJoseph Taboada - Department of Veterinary Clinical SciencesGiselle Hosgood - Department of Veterinary Clinical SciencesBeth P. Partington - Department of Veterinary Clinical SciencesFreadéric P. Gaschen
- Publication Details
- Journal of veterinary internal medicine, Vol.14(2), pp.157-164
- Publisher
- Blackwell Publishing Ltd
- Edition
- Revised March 12, 1999, and July 1, 1999; Accepted October 19, 1999
- Number of pages
- 8
- Identifiers
- 991005591574607891
- Copyright
- © 2000 American College of Veterinary Internal Medicine
- Murdoch Affiliation
- School of Veterinary Medicine
- Language
- English
- Resource Type
- Journal article
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Source: InCites
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- Collaboration types
- Domestic collaboration
- International collaboration
- Citation topics
- 1 Clinical & Life Sciences
- 1.213 Thyroid Disorders
- 1.213.168 Thyroid Disorders
- Web Of Science research areas
- Veterinary Sciences
- ESI research areas
- Plant & Animal Science