Efficacy and safety of once versus twice daily administration of methimazole in cats with hyperthyroidism.
OBJECTIVE
To determine whether once daily administration of methimazole was as effective and safe as twice daily administration in cats with hyperthyroidism.


METHODS
Randomized, nonblinded, clinical trial.


METHODS
40 cats with newly diagnosed hyperthyroidism.


METHODS
Cats were randomly assigned to receive 5 mg of methimazole, PO, once daily (n = 25) or 2.5 mg of methimazole, PO, twice daily (15). A complete physical examination, including measurement of body weight; CBC; serum biochemical analyses, including measurement of serum thyroxine concentration; and urinalysis were performed, and blood pressure was measured before and 2 and 4 weeks after initiation of treatment.


RESULTS
Serum thyroxine concentration was significantly higher in cats given methimazole once daily, compared with cats given methimazole twice daily, 2 weeks (3.7 vs 2.0 micro +/- g/dL) and 4 weeks (3.2 vs 1.7 microg/dL) after initiation of treatment. In addition, the proportion of cats that were euthyroid after 2 weeks of treatment was lower for cats receiving methimazole once daily (54%) than for cats receiving methimazole twice daily (87%). Percentages of cats with adverse effects (primarily gastrointestinal tract upset and facial pruritus) were not significantly different between groups.


CONCLUSIONS
Results suggest that once daily administration of methimazole was not as effective as twice daily administration in cats with hyperthyroidism and cannot be recommended for routine use.
Trepanier
Lauren A
LA
Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, USA.
Hoffman
Stacey B
SB
Kroll
Mandy
M
Rodan
Ilona
I
Challoner
Laura
L
D000284:Administration, Oral; D000818:Animals; D013956:Antithyroid Agents / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D002371:Cat Diseases / Q000188:drug therapy*; D002415:Cats; D004334:Drug Administration Schedule / Q000662:veterinary; D006980:Hyperthyroidism / Q000188:drug therapy / Q000662:veterinary*; D008713:Methimazole / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D012449:Safety; D013974:Thyroxine / Q000097:blood; D016896:Treatment Outcome
D013956:Antithyroid Agents; D008713:Methimazole; D013974:Thyroxine