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Fact Sheets


Fact Sheet 4 – Propranolol (Inderal)

The most commonly used antithyroid drugs are Propylthiouracil (P.T.U.) and Tapazole (Methimazole). These drugs act to prevent the thyroid gland from manufacturing thyroid hormone, and thus the symptoms of hyperthyroidism will gradually subside.

You will probably begin to feel better within two weeks, you will feel a difference by six weeks, and feel well in 10-14 weeks. You will probably take the medication for 6-12 months. Your doctor will check at six months, nine months and twelve months approximately, to see if P.T.U. is still needed. If your thyroid gland now functions normally, your family doctor will still check you periodically to be sure that your thyroid hormone level (T4) remains within the normal range or just above (normal T4 range – 50-165nmol/L). Most patients feel better with a T4 level in the upper half of normal (110-165nmol/L).

If taking antithyroid drugs, P.T.U. or Tapazole, and you develop a rash, itching, hives, joint pains, a fever or sore throat, stop taking the drug and call your doctor immediately as you could be having an allergic reaction.

If you have any fever or infection while you are taking an antithyroid drug, your doctor will check your white blood cell count. If normal, treatment with antithyroid drugs can start again. If the white blood cell count is decreased, your doctor will use another type of treatment to control your hyperthyroidism -radioactive iodine (RAI) or surgery.

Radioactive iodine is used to control hyperthyroidism because it goes only into the thyroid gland and destroys thyroid tissue, leaving the body within a few days. Any remaining RAI decays into a non-radioactive state. Most patients need only one dose to control their hyperthyroidism: others may need additional doses.

Radioactive iodine is tasteless, and usually given in a glass of water. It is painless and no fasting is necessary – do not be afraid of this excellent treatment.

You should feel well within three to six months after radioactive iodine treatment. Once your thyroid level is normal yearly blood tests should be done to watch for possible development of hypothyroidism. Most patients will become hypothyroid.


  • should avoid cough/cold medicines with decongestants as they can cause restlessness and extra stimulation of the heart.
  • should avoid stimulants such a coffee, alcohol, tobacco or chocolate while in a very hyperthyroid state.
  • should avoid excess iodine found in kelp (dulse) and some asthma medications, vitamins, cough medicines, suntan lotions, salt substitutes. Please read the labels.
  • the preferred antithyroid drug during pregnancy, in doses lower than with non pregnant women, is propylthiouracil (PTU) and can be used when breast feeding, as only negligible amounts actually get into the milk.
  • you cannot donate blood if you are taking antithyroid medication.
  • if you forget a dose of antithyroid drug or other medications contact your doctor for guidance as to the best way to resume medication.
  • Haldol: A hyperthyroid patient taking Haldol may develop rigidity and the inability to walk.

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