Part of the study was presented as an oral abstract at the 16th ECVIM-CA Congress, Amsterdam, Netherlands, September 2006
Duration of T4 Suppression in Hyperthyroid Cats Treated Once and Twice Daily with Transdermal Methimazole
Version of Record online: 9 FEB 2013
Copyright © 2013 by the American College of Veterinary Internal Medicine
Journal of Veterinary Internal Medicine
Volume 27, Issue 2, pages 377–381, March/April 2013
How to Cite
Boretti, F.S., Sieber-Ruckstuhl, N.S., Schäfer, S., Baumgartner, C., Riond, B., Hofmann-Lehmann, R. and Reusch, C.E. (2013), Duration of T4 Suppression in Hyperthyroid Cats Treated Once and Twice Daily with Transdermal Methimazole. Journal of Veterinary Internal Medicine, 27: 377–381. doi: 10.1111/jvim.12040
- Issue online: 15 MAR 2013
- Version of Record online: 9 FEB 2013
- Manuscript Accepted: 6 DEC 2012
- Manuscript Revised: 13 NOV 2012
- Manuscript Received: 27 AUG 2012
- PLO ;
Transdermal methimazole is an acceptable alternative to oral treatment for hyperthyroid cats. There are, however, no studies evaluating the duration of T4 suppression after transdermal methimazole application. Such information would be valuable for therapeutic monitoring.
To assess variation in serum T4 concentration in hyperthyroid cats after once- and twice-daily transdermal methimazole administration.
Twenty client-owned cats with newly diagnosed hyperthyroidism.
Methimazole was formulated in a pluronic lecithin organogel-based vehicle and applied to the pinna of the inner ear at a starting dose of 2.5 mg/cat q12h (BID group, 10 cats) and 5 mg/cat q24h (SID group, 10 cats). One and 3 weeks after starting treatment, T4 concentrations were measured immediately before and every 2 hours after gel application over a period of up to 10 hours.
Significantly decreased T4 concentrations were observed in week 1 and 3 compared with pretreatment concentrations in both groups. All cats showed sustained suppression of T4 concentration during the 10-hour period, and T4 concentrations immediately before the next methimazole treatment were not significantly different compared with any time point after application, either in the BID or SID groups.
Because transdermal methimazole application led to prolonged T4 suppression in both the BID and SID groups, timing of blood sampling does not seem to be critical when assessing treatment response.