Block and replace regime (in thyrotoxicosis)

An alternative to treatment with antithyroid drugs alone, block and replace therapy comprises of

• constant dose if thionamide (e.g. - carbimazole 40 mg daily) to block thyroid hormone production
• add levothyroxine to maintaineuthyroidiims (e.g. - 100 µg daily for women, 125 µg daily for men)

This regime may be continued for 18 months, and propylthiouracil may be used if carbimazole is not well tolerated.

Disadvantages of this regime are that the large number of tablets may result in poor compliance and it is argued that the physician is unable to gauge the likelihood of relapse. Advantages of this regimen however are that under or over treatment is avoided whilst better use is made of carbimazole's immunosuppressive action.

Reference:

• (1) Vaidya B, Pearce SH. Diagnosis and management of thyrotoxicosis. BMJ. 2014;349:g5128