Thyroxine Replacement

There are three well-tested, brand name levothyroxine preparations available in the market for the treatment of thyroid patients:

  1. Levothroid,
  2. Levoxyl, and
  3. Synthroid.

Although there may be differences in the manufacturing, composition (dyes and fillers), and absorption rates among these preparations, each of these brand-name products is reliable and offers predictable results. Although changing from one brand to another does not usually cause problems, it is preferable to take the same brand consistently.

The bioavailability of levothyroxine may differ to some extent among marketed brands. Once the patient is stabilized on a particular brand of levothyroxine sodium, caution should be exercised when a change in drug product brand is implemented.

It has been shown that differences in formulations of levothyroxine, despite an identical content of active ingredient, may be associated with differences in fractional gastrointestinal absorption. These differences may not be observed through measurement of total T 3 and T 4 serum levels. It is therefore, recommended that patients who are switched from one levothyroxine formulation to another be retitrated to the desired thyroid function. Accuracy in retitration can best be achieved by using sensitive thyrotropin assays.

Side Effects of Thyroid Medications

  1. Tachycardia (palpitations)
  2. Atrial fibrillation (irregular pulse)
  3. Osteoporosis (bone thinning)
  4. Tremors (shakiness).

Usually the replacement therapy is taken for three months. Once the symptoms are in control, it would be better to reduce the dose slowly and gradually, but these decisions are individualized depending on patient’s clinical and lab profile. Hence it might have been prudent to reduce it first to 150 daily and later to 125 a day.

Sometimes, the patient shows symptoms of hypothyroidism after taking medication for some time. Such symptoms should be reported to the doctor, So that he can adjust the dose accordingly.

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