Abstract: The present invention relates to a transdermal administration preparation for external application such as ointment, cream and the like, which contains SMP-114 or leflunomide or a pharmaceutically acceptable acid addition salt thereof as an active ingredient. The present invention further relates to a pharmaceutical composition for transdermal administration which contains, a) as an active ingredient, N-(4-trifluoromethylphenyl)-5-methylisoxazole-4-carboxamide or an active motabolite thereof or a pharmaceutically acceptable salt thereof; and B)(1) a carrier for transdermal administration which contains a base for dissolution in a proportion of not less than 40 w/w %, or (2) a carrier for transdermal administration which contains a hydrophobic base for suspension having no polar group in a molecule in a proportion of not less than 70 w/w %.