Trans-pinnal movement of methimazole: an in vitro study showing that methimazole can cross from the inner to outer pinna of cats

Hill, Kate E., Chambers, J. Paul, Jones, Boyd R., Bolwell, Charlotte F., Aberdein, Dani and Mills, Paul C. (2015) Trans-pinnal movement of methimazole: an in vitro study showing that methimazole can cross from the inner to outer pinna of cats. Journal of Feline Medicine and Surgery, 17 12: 1005-1011. doi:10.1177/1098612X14567548


Author Hill, Kate E.
Chambers, J. Paul
Jones, Boyd R.
Bolwell, Charlotte F.
Aberdein, Dani
Mills, Paul C.
Title Trans-pinnal movement of methimazole: an in vitro study showing that methimazole can cross from the inner to outer pinna of cats
Journal name Journal of Feline Medicine and Surgery   Check publisher's open access policy
ISSN 1532-2750
1098-612X
Publication date 2015-12-01
Year available 2015
Sub-type Article (original research)
DOI 10.1177/1098612X14567548
Open Access Status Not yet assessed
Volume 17
Issue 12
Start page 1005
End page 1011
Total pages 7
Place of publication London, United Kingdom
Publisher SAGE Publications
Language eng
Formatted abstract
Objectives The aim of the study was to determine if methimazole applied in a transdermal formulation to the internal pinna will cross to the external pinna in an in vitro Franz cell model.

Methods The ears from six cats were harvested soon after death. Whole ears were mounted onto Franz-type diffusion cells with the stratum corneum of the inner pinnae uppermost. A commercial transdermal preparation containing methimazole (0.1 ml/10 mg) was applied to the inner pinnae. At 1, 2, 4, 6, 8, 12, 18, 24 and 30 h, a 200 µl sample of reservoir solution was removed to determine the methimazole concentration by high-performance liquid chromatography. The ears were then dissected, separating the internal pinna from the cartilage and the external pinna, before the methimazole concentration was measured at each site. The thickness of the different regions of the ear was measured on paraffin histology sections.

Results
Mean ± SD methimazole concentrations at 30 h for the right and left ear, respectively, were: inner ear, 1.25 ± 0.53 mg/g, 0.39 ± 0.26 mg/g; cartilage, 1.36 ± 0.47 mg/g, 0.33 ± 0.20 mg/g; and outer ear, 1.0 ± 0.32 mg/g, 0.33 ± 0.14 mg/g. There was a difference between the left and right ears (P <0.001). Minimal methimazole concentrations were detected in the receptor fluid. The mean methimazole concentration absorbed by the skin after application of 10 mg was, for the right ear, 3.65 ± 1.27 mg/g and, for the left, 1.08 ± 0.27 mg/g. There was no correlation between methimazole concentrations and thickness of each region of the ear.

Conclusions and relevance Methimazole in a lipophilic vehicle applied to the inner pinna will penetrate to the outer pinna of cats in an in vitro model, which may have safety implications for humans associated with cats treated with transdermal methimazole. Substantial inter-individual variation was found. Further research is required in the area of transdermal penetration of drugs in cats.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2016 Collection
School of Veterinary Science Publications
 
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