Transdermal application of methimazole in hyperthyroid cats: a long-term follow-up study - PubMed (original) (raw)

Transdermal application of methimazole in hyperthyroid cats: a long-term follow-up study

Felicitas S Boretti et al. J Feline Med Surg. 2014 Jun.

Abstract

Transdermal methimazole is suggested as an alternative to oral therapy for hyperthyroid cats that are difficult to pill. However, no information on long-term management with this treatment is available. Our objective was therefore to retrospectively evaluate the efficacy and safety of long-term transdermal methimazole treatment in hyperthyroid cats. Sixty cats with newly diagnosed hyperthyroidism and available long-term follow-up information were included. Methimazole was formulated in a pluronic lecithin organogel-based vehicle and was applied to the pinna of the inner ear. Cats were re-evaluated at regular intervals. Median (range) follow-up was 22.6 months (3.6-88.4 months). Clinical improvement was observed in all cats and side effects were rare (mild transient gastrointestinal signs: n = 3; erythema of the pinna: n = 2, necessitating a switch to oral medication). Despite a significant decrease, with median T4 concentrations within the reference interval during the follow-up period, several cats repeatedly had T4 concentrations in the thyrotoxic and hypothyroid range. Maximal and minimal daily doses during the follow-up period were 15.0 and 1.0 mg, respectively; they were significantly higher than the starting dose after 24-36 months of therapy. Although the majority of owners were highly satisfied with the treatment, several admitted not treating their cat regularly. Transdermal methimazole is a safe option for the long-term management of feline hyperthyroidism. However, it seems difficult to keep the T4 concentrations constantly within the reference interval. Higher doses can be expected after prolonged treatment and, despite the convenience of transdermal application, owner compliance should be assessed regularly.

© ISFM and AAFP 2013.

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Conflict of interest statement

The authors do not have any potential conflicts of interest to declare.

Figures

Figure 1

Figure 1

Scatter plot of serum T4 concentrations before and at different time points during long-term transdermal methimazole therapy. The median is indicated by a horizontal line. The horizontal dotted lines represent the reference T4 concentrations. *_P_Wilcoxon = 0.0004; **_P_Wilcoxon <0.0001

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