Serum total thyroxine, total triiodothyronine, free thyroxine, and thyrotropin concentrations in epileptic dogs treated with anticonvulsants.
OBJECTIVE
To determine whether administration of phenobarbital, potassium bromide, or both drugs concurrently was associated with abnormalities in baseline serum total thyroxine (T4), triiodothyronine (T3), free T4, or thyrotropin (thyroid-stimulating hormone; TSH) concentrations in epileptic dogs.


METHODS
Prospective case series.


METHODS
78 dogs with seizure disorders that did not have any evidence of a thyroid disorder (55 treated with phenobarbital alone, 15 treated with phenobarbital and bromide, and 8 treated with bromide alone) and 150 clinically normal dogs that were not receiving any medication.


METHODS
Serum total T4, total T3, free T4, and TSH concentrations, as well as serum concentrations of anticonvulsant drugs, were measured in the 78 dogs with seizure disorders. Reference ranges for hormone concentrations were established on the basis of results from the 150 clinically normal dogs.


RESULTS
Total and free T4 concentrations were significantly lower in dogs receiving phenobarbital (alone or with bromide), compared with concentrations in clinically normal dogs. Administration of bromide alone was not associated with low total or free T4 concentration. Total T3 and TSH concentrations did not differ among groups of dogs.


CONCLUSIONS
Results indicate that serum total and free T4 concentrations may be low (i.e., in the range typical for dogs with hypothyroidism) in dogs treated with phenobarbital. Serum total T3 and TSH concentrations were not changed significantly in association with phenobarbital administration. Bromide treatment was not associated with any significant change in these serum thyroid hormone concentrations.
Kantrowitz
L B
LB
Oradell Animal Hospital, NJ 07649, USA.
Peterson
M E
ME
Trepanier
L A
LA
Melián
C
C
Nichols
R
R
D000818:Animals; D000927:Anticonvulsants / Q000097:blood / Q000627:therapeutic use*; D001965:Bromides / Q000097:blood / Q000627:therapeutic use; D004283:Dog Diseases / Q000097:blood / Q000188:drug therapy*; D004285:Dogs; D004359:Drug Therapy, Combination; D004827:Epilepsy / Q000097:blood / Q000188:drug therapy / Q000662:veterinary*; D005260:Female; D008297:Male; D010634:Phenobarbital / Q000097:blood / Q000627:therapeutic use; D017680:Potassium Compounds / Q000097:blood / Q000627:therapeutic use; D011446:Prospective Studies; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*
D000927:Anticonvulsants; D001965:Bromides; D017680:Potassium Compounds; D014284:Triiodothyronine; D013972:Thyrotropin; C039004:potassium bromide; D013974:Thyroxine; D010634:Phenobarbital