Efficacy and safety of once versus twice daily administration of methimazole in cats with hyperthyroidism.

Abstract

OBJECTIVE:

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

DESIGN:

Randomized, nonblinded, clinical trial.

ANIMALS:

40 cats with newly diagnosed hyperthyroidism.

PROCEDURE:

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 AND CLINICAL RELEVANCE:

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.

• Authors: Lauren A Trepanier, Stacey B Hoffman, Mandy Kroll, Ilona Rodan, Laura Challoner
• Journal: Journal of the American Veterinary Medical Association (J Am Vet Med Assoc) Vol. 222 Issue 7 Pg. 954-8 (Apr 01 2003) ISSN: 0003-1488 [Print] United States
• PMID: 12685785 (Publication Type: Clinical Trial, Journal Article, Randomized Controlled Trial, Research Support, Non-U.S. Gov't)

Chemical References

• Antithyroid Agents
• Methimazole
• Thyroxine

Topics

• Administration, Oral
• Animals
• Antithyroid Agents (administration & dosage, adverse effects, therapeutic use)
• Cat Diseases (drug therapy)
• Cats
• Drug Administration Schedule (veterinary)
• Hyperthyroidism (drug therapy, veterinary)
• Methimazole (administration & dosage, adverse effects, therapeutic use)
• Safety
• Thyroxine (blood)
• Treatment Outcome