The present invention relates to compositions, in particular for the treatment of hyperthyreosis (also designated hyperthyroidism), especially in cats. These compositions are formulated for transdermal administration of an active substance and may, for example, be applied into the auricle (or pinna) of the cat. They comprise an active agent such as methimazole (or 2-mercapto-1-methylimidazole) or carbimazole, at least one wax, at least one fatty oil, and optionally an emulsifier. As emulsifier a nanocarrier may be used, for example. Unimolecular nanocarriers of dendritic structure are preferred, wherein the nanocarrier comprises a dendritic core and at least two shells, wherein an inner shell is coupled to the dendritic core via a first linker, and an outer shell is coupled to the inner shell via a second linker. In one embodiment, the composition is provided as a stick, in another, a semi-solid formulation in a suitable applicator which may contain one or more dosage units.
