title: Transdermal application of methimazole in hyperthyroid cats: a long-term follow-up study.
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.
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Switzerland fboretti@vetclinics.uzh.ch.
authors.forename: Felicitas S
authors.initials: FS
authors.lastname: Boretti
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Switzerland.
authors.forename: Nadja S
authors.initials: NS
authors.lastname: Sieber-Ruckstuhl
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Switzerland.
authors.forename: Sandra
authors.initials: S
authors.lastname: Schäfer
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Switzerland.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Gerber
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Switzerland.
authors.forename: Claudia
authors.initials: C
authors.lastname: Baumgartner
authors.affiliation: Clinical Laboratory, Vetsuisse Faculty, University of Zurich, Switzerland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Riond
authors.affiliation: Clinical Laboratory, Vetsuisse Faculty, University of Zurich, Switzerland.
authors.forename: Regina
authors.initials: R
authors.lastname: Hofmann-Lehmann
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Switzerland.
authors.forename: Claudia E
authors.initials: CE
authors.lastname: Reusch
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D013956:Antithyroid Agents / Q000627:therapeutic use*; D002371:Cat Diseases / Q000188:drug therapy*; D002415:Cats; D054644:Ear Auricle; D005260:Female; D005500:Follow-Up Studies; D006980:Hyperthyroidism / Q000188:drug therapy / Q000662:veterinary*; D008297:Male; D008713:Methimazole / Q000627:therapeutic use*; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D013956:Antithyroid Agents; D008713:Methimazole