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Duration of T4 suppression in hyperthyroid cats treated once and twice daily with transdermal methimazole


Boretti, F S; Sieber-Ruckstuhl, N S; Schäfer, S; Baumgartner, C; Riond, B; Hofmann-Lehmann, R; 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(2):377-381.

Abstract

BACKGROUND: 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. OBJECTIVE: To assess variation in serum T4 concentration in hyperthyroid cats after once- and twice-daily transdermal methimazole administration. ANIMALS: Twenty client-owned cats with newly diagnosed hyperthyroidism. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Abstract

BACKGROUND: 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. OBJECTIVE: To assess variation in serum T4 concentration in hyperthyroid cats after once- and twice-daily transdermal methimazole administration. ANIMALS: Twenty client-owned cats with newly diagnosed hyperthyroidism. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

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4 citations in Web of Science®
6 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Veterinary Clinic > Department of Small Animals
05 Vetsuisse Faculty > Veterinary Clinic > Department of Farm Animals
Dewey Decimal Classification:570 Life sciences; biology
630 Agriculture
Language:English
Date:2013
Deposited On:22 Feb 2013 09:25
Last Modified:05 Apr 2016 16:33
Publisher:Wiley-Blackwell
ISSN:0891-6640
Publisher DOI:https://doi.org/10.1111/jvim.12040
PubMed ID:23398124

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