In humans, oral cholecystographic agents such as ipodate and iopanoic acid have been used to treat hyperthyroidism because of their rapid action and excellent safety record. The principle effect of oral cholecystographic agents is inhibition of deiodinases that are responsible for the peripheral conversion of thyroxine (T4) to 3,5,3'-triiodothyronine (T3) (Gallagher & Panciera, 2009).
Ipodate is the main oral cholecystographic agent that has been evaluated for the treatment of hyperthyroidism in cats. Administration of ipodate to cats with experimentally induced hyperthyroidism caused a significant reduction in serum T3 concentration and an increase in bodyweight. Ipodate treatment of cats with spontaneous hyperthyroidism resulted in effective control of the disease in 66% of cases.
Iopanoic acid has had limited trials and appears to have similar effects in controlling clinical disease in hyperthyroidism cases.
This drug may be beneficial for acute management of thyrotoxicosis in some cats, but is not suitable for long-term management.