Selection of tapazole (MMI) and propylthioxypyrimethamine (PTU): 1. The biological effectiveness of tapazole has a long duration of action, and some studies have shown that the clinical effects of a single dose and a split dose are the same. 2. The immunomodulatory effect of PTU is better. There is direct inhibition of the conversion of T4 to T3, with a faster onset of action. There are considered to cause less side effects of leukopenia. 3. For hyperthyroidism and pregnancy, PTU is generally preferred, and the drug passes through the placenta less often than tapazole. For the selection of pregnant women, the latest development is that the main teratogenic effects of tapazole are skin defects, which occur mainly in early pregnancy. Therefore, the choice of PTU in the first trimester of pregnancy is currently advocated abroad, with a switch to tapazole in the middle and second trimesters. In addition to the above points, the two drugs have the following differences: 1. It is generally believed that the effect of PTU leading to neutropenia is not related to its dose, but somewhat similar to an allergic reaction; such side effects of tabazol are dose related and mainly occur at higher doses during the initial treatment period. Patients using these two drugs must be alerted to neutropenia once sore throat and fever occur. 2. In the preparation of patients with more severe hyperthyroidism before iodine 131 treatment, only tapazole should be used because its effect of inhibiting iodine uptake by thyroid tissue lasts for a short time (24 hours), while PTU lasts for weeks to months. 3. PTU is preferred for resuscitation of thyroid crisis. 4. PTU also has the side effect of causing ANCA-associated small vessel vasculitis. 5, PTU and tabazol can both produce a decrease in WBC and abnormal liver function, but there are some differences. (1) So far, almost all foreign data show that the rate of PTU causing granular deficiency is greater than that of MMI and CMI, including retrospective and prospective. This may have historical reasons, because at the early stage of thioureas (propylthiouracil, methylthiouracil) use, their incidence of granular deficiency was high, reaching 2-3%, when there was no good antibiotic treatment until patients died, so for quite some time thioureas were not widely used, but only as a back-up drug for patients who could not tolerate MMI treatment. In this case, on the one hand, physicians are not experienced in the clinical use of PTU, and on the other hand, since patients taking PTU are often patients who cannot tolerate MMI, the comparison between them and MMI is not well comparable. Based on personal experience, it seems that PTU causes less decrease in WBC. (2) In terms of liver function, PTU is an “all or nothing” side effect, while MMI is dose-related. PTU mostly causes elevated liver enzymes and MMI mostly causes biliary stasis. In addition, since the liver damage caused by PTU is mostly autoimmune related, it can be treated with small doses of hormones as appropriate. (3) MMI and PTU are cross-allergic, which must be noted! Any granular deficiency, severe liver damage, or exfoliative dermatitis should never be tried with another drug! Even if the side effects do not reach that serious level, the drug should be changed after the allergy period. mMI allergy, if it is a mild white blood cell drop, common dermatitis, mild liver damage, it is possible to change the drug. If a mild allergy to PTU occurs in a pregnant or nursing woman who can only use PTU, even desensitization methods can be used and about half of the people can be desensitized. (4) The side effects of MMI are dose-dependent; the side effects of PTU are not dose-dependent!