Page 824 - Small Animal Internal Medicine, 6th Edition

796 PART VI Endocrine Disorders

TABLE 48.6
VetBooks.ir Indications, Contraindications, and Disadvantages of the Four Modes of Therapy for Hyperthyroidism in Cats

RELATIVE
THERAPY INDICATIONS CONTRAINDICATIONS DISADVANTAGES

Methimazole, Long-term therapy for all forms of None Daily therapy required; no
propylthiouracil, hyperthyroidism; initial therapy to effect on growth of thyroid;
carbimazole stabilize cat’s condition and assess mild adverse reactions
kidney function before thyroidectomy common; severe reactions
or radioactive iodine possible
Iodine-restricted Therapy for all forms of Concurrent administration Rigid requirements to ensure
diet hyperthyroidism; initial therapy to of antithyroid absolutely no access to any
stabilize cat’s condition and assess medications not other source of dietary
kidney function before thyroidectomy recommended by iodine; cat must be kept
or radioactive iodine; reversible manufacturer of the diet strictly indoors; problematic
treatment option for cats that develop in multicat households; long
adverse reactions to methimazole or term consequences of iodine
for clients unable to administer restriction are unknown
methimazole to their cat
Thyroidectomy Unilateral lobe involvement; bilateral Ectopic thyroid lobe; Anesthetic risks; relapse of
lobe involvement, asymmetric sizes metastatic carcinoma; disease; postoperative
bilateral, symmetric, complications, especially
large lobes (high risk of hypocalcemia
hypocalcemia); severe
systemic signs; cardiac
arrhythmias or failure;
renal insufficiency
Radioactive iodine Therapy for all forms of Renal insufficiency Limited availability;
( 131 l) hyperthyroidism; treatment of choice hospitalization time;
for ectopic thyroid lobe and thyroid potential for retreatment;
carcinoma hazardous to humans

TABLE 48.7
Abnormalities Associated With Methimazole Therapy in 262 Cats With Hyperthyroidism

CLINICAL SIGNS AND TIME TO DEVELOP (DAYS)
PATHOLOGY PERCENTAGE OF CATS MEAN RANGE

Clinical Signs
Anorexia 11 24 1-78
Vomiting 11 22 7-60
Lethargy 9 24 1-60
Excoriations 2 21 6-40
Bleeding 2 31 15-50

Clinical Pathology
Positive antinuclear antibody titer 22 91 10-870
Eosinophilia 11 57 12-490
Lymphocytosis 7 25 14-90
Leukopenia 5 23 10-41
Thrombocytopenia 3 37 14-90
Agranulocytosis 2 62 26-95
Hepatopathy 2 39 15-60

Adapted from Peterson ME, Kintzer PP, Hurvitz AI: Methimazole treatment of 262 cats with hyperthyroidism, J Vet Intern Med 2:150, 1988.