Thyroid function and serum hepatic enzyme activity in dogs after phenobarbital administration

Tracy L. Gieger; Giselle Hosgood; Joseph Taboada; Karen J. Wolfsheimer; Peter B. Mueller

doi:10.1111/j.1939-1676.2000.tb01167.x

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Thyroid function and serum hepatic enzyme activity in dogs after phenobarbital administration

Journal article

Open access

Peer reviewed

Thyroid function and serum hepatic enzyme activity in dogs after phenobarbital administration

Tracy L. Gieger, Giselle Hosgood, Joseph Taboada, Karen J. Wolfsheimer and Peter B. Mueller

Journal of veterinary internal medicine, Vol.14(3), pp.277-281

2000

DOI: https://doi.org/10.1111/j.1939-1676.2000.tb01167.x

PMCID: PMC7167147

PMID: 10830541

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Abstract

Anticonvulsants

Epilepsy

Hepatotoxicity

Hypothyroidism

Seizures

Phenobarbital is the drug of choice for control of canine epilepsy. Phenobarbital induces hepatic enzyme activity, can be hepatotoxic, and decreases serum thyroxine (T4) concentrations in some dogs. The duration of liver enzyme induction and T4 concentration decreases after discontinuation of phenobarbital is unknown. The purpose of this study was to characterize the changes in serum total T4 (TT4), free T4 (FT4), thyroid-stimulating hormone (TSH), cholesterol and albumin concentrations, and activities in serum of alanine aminotransferase (ALT), alkaline phosphatase (ALP), and gamma-glutamyl transferase (GGT) after discontinuation of long-term phenobarbital administration in normal dogs. Twelve normal dogs were administered phenobarbital at a dosage of approximately 4.4–6.6 mg/kg PO ql2h for 27 weeks. Blood was collected for analysis before and after 27 weeks of phenobarbital administration and then weekly for 10 weeks after discontinuation of the drug. The dogs were clinically normal throughout the study period. Serum ALT and ALP activity and TSH and cholesterol concentrations were significantly higher than baseline at week 27. Serum T4 and FT4 were significantly lower. Serum albumin and GGT were not changed from baseline at week 27. Changes in estimate of thyroid function (TT4, FT4, TSH) persisted for 1–4 weeks after discontinuation of phenobarbital, whereas changes in hepatic enzyme activity (ALT, ALP) and cholesterol concentration resolved in 3–5 weeks. To avoid false positive results, it is recommended that thyroid testing be performed at least 4 weeks after discontinuation of phenobarbital administration. Elevated serum activity of hepatic enzymes 6–8 weeks after discontinuation of phenobarbital may indicate hepatic disease.

Details

Title: Thyroid function and serum hepatic enzyme activity in dogs after phenobarbital administration
Authors/Creators: Tracy L. Gieger - Louisiana State University
Giselle Hosgood - Louisiana State University
Joseph Taboada - Louisiana State University
Karen J. Wolfsheimer - Baton Rouge Clinic
Peter B. Mueller - Purdue University West Lafayette
Publication Details: Journal of veterinary internal medicine, Vol.14(3), pp.277-281
Publisher: Blackwell Publishing Ltd
Identifiers: 991005592657007891
Murdoch Affiliation: School of Veterinary Medicine
Language: English
Resource Type: Journal article

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Collaboration types: Domestic collaboration
Citation topics: 1 Clinical & Life Sciences; 1.222 Epilepsy & Seizures; 1.222.143 Epilepsy Treatment
Web Of Science research areas: Veterinary Sciences
ESI research areas: Plant & Animal Science