Mika Note

Carbimazole(CBZ)可完全轉換為Methimazole(MMI)，故兩者可視為一樣的東西

藥物動力學與藥效學差異

1. The serum half-life of MMI is four to six hours, whereas that of PTU is 75 minutes.

2. The intrathyroidal MMI concentration, which can reach a thyroid-to-serum ratio of 100:1, remains high for up to 20 hours, considerably longer than that of PTU.

3. Perchlorate discharge tests, which are a measure of inhibition of iodine organification, demonstrate the superiority of MMI over PTU. In one study, perchlorate discharged 37 percent of the radioiodine tracer 24 hours after a single 15 mg dose of MMI, versus only 8.6 percent after a 300 mg dose of PTU

所以選擇CBZ作為首選的原因是

1. More rapid achievement of euthyroidism

2. Once-daily dosing and better compliance

3. Little or no effect on subsequent success of radioiodine therapy (unlike PTU, which is associated with an increase in radioiodine failure rates)

4. Less toxicity

但某些時候會是PTU勝選，因為…

1. In pregnant women during their first trimester

2. In patients with life-threatening thyrotoxicosis or thyroid storm (because of PTU's ability to inhibit peripheral conversion of T4 to T3) 

3. In patients with adverse reactions to MMI (other than agranulocytosis) who are not candidates for radioiodine or surgery

補充

PTU可用在first trimester pregnancy有中等至嚴重的甲亢，進入second trimester則建議轉換為MMI (CBZ)

Hyperthyroidism合併hyperadrenergic symptoms也可加入beta-blocker，但須密切監控，且該停就要快停，因為擔心fetal growth restriction, hypoglycemia, respiratory depression及 bradycardia導致胎兒受到不必要的傷害

 同場佳映兩張比較圖片