An elderly male patient sought medical attention due to "intolerance of methimazole tablet and radioiodine treatment for six months". There was a contradiction between the efficacy and adverse drug reaction. Based on the patient′s wishes, the clinical treatment of methimazole cream was adopted. During the follow-up of 12 weeks, the patient′s symptoms were significantly improved, the indicators of thyroid function declined to normal level, and there were no significant abnormalities in indicators for routine blood test and liver function. The case broke away from conventions in medication selection, showing that the initial and reduced dosage was explored and formulated by combination of the theoretical basis of pharmacodynamics, pharmacokinetics and physician′s clinical experience. It also provided clinical reference for the use of the topical formulation.