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Thyroid Hormones  (Systemic)

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Brand Names

Some commonly used brand names are:

In the U.S.—

  • Armour Thyroid5
  • Cytomel2
  • Levo-T1
  • Levothroid1
  • Levoxyl1
  • Synthroid1
  • Thyrar5
  • Thyroid Strong5
  • Thyrolar3
  • Triostat2
  • Westhroid5

In Canada—

  • Cytomel2
  • Eltroxin1
  • PMS-Levothyroxine Sodium1
  • Synthroid1

Note:

For quick reference, the following thyroid hormones are numbered to match the corresponding brand names.
This information applies to the following medicines:
1.  Levothyroxine (lee-voe-thye-ROX-een)
2.  Liothyronine (lye-oh-THYE-roe-neen)
3.  Liotrix (LYE-oh-trix)
4.  Thyroglobulin (thye-roe-GLOB-yoo-lin)*
5.  Thyroid (THYE-roid)
‡  Generic name product may be available in the U.S.
§  Generic name product may be available in Canada
*  Not commercially available in the U.S.
†  Not commercially available in Canada

Category


Description

Thyroid medicines belong to the general group of medicines called hormones. They are used when the thyroid gland does not produce enough hormone. They are also used to help decrease the size of enlarged thyroid glands (known as goiter) and to treat thyroid cancer.

These medicines are available only with your doctor's prescription, in the following dosage forms:



Before Using This Medicine

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For thyroid hormones, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to thyroid hormones. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy—Use of proper amounts of thyroid hormone during pregnancy has not been shown to cause birth defects or other problems. However, your doctor may want you to change your dose while you are pregnant. This will make regular visits to your doctor important.

Breast-feeding—Use of proper amounts of thyroid hormones by mothers has not been shown to cause problems in nursing babies.

Children—Thyroid hormones have been tested in children and have not been shown to cause different side effects or problems in children than they do in adults.

Older adults—This medicine has been tested and has not been shown to cause different side effects or problems in older people than it does in younger adults. However, a different dose may be needed in the elderly. Therefore, it is important to take the medicine only as directed by the doctor.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking thyroid hormones, it is especially important that your health care professional know if you are taking any of the following:

Other medical problems—The presence of other medical problems may affect the use of thyroid hormones. Make sure you tell your doctor if you have any other medical problems especially:


Proper Use of This Medicine

Use this medicine only as directed by your doctor. Do not use more or less of it, and do not use it more often than your doctor ordered. Your doctor has prescribed the exact amount your body needs and if you take different amounts, you may experience symptoms of an overactive or underactive thyroid. Take it at the same time each day to make sure it always has the same effect.

If your condition is due to a lack of thyroid hormone, you may have to take this medicine for the rest of your life. It is very important that you do not stop taking this medicine without first checking with your doctor.

Dosing—

The dose of these medicines will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of these medicines. If your dose is different, do not change it unless your doctor tells you to do so.

The number of tablets that you take depends on the strength of the medicine. The amount of thyroid hormone that you need to take every day depends on the results of your thyroid tests. However, treatment is usually started with lower doses that are increased a little at a time until you are taking the full amount. This helps prevent side effects.

Missed dose—

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses. If you miss 2 or more doses in a row or if you have any questions about this, check with your doctor.

Storage—

To store this medicine:


Precautions While Using This Medicine

It is very important that your doctor check your progress at regular visits, to make sure that this medicine is working properly.

If you have certain kinds of heart disease, this medicine may cause chest pain or shortness of breath when you exert yourself. If these occur, do not overdo exercise or physical work. If you have any questions about this, check with your doctor.

Before having any kind of surgery (including dental surgery) or emergency treatment, tell the medical doctor or dentist in charge that you are taking this medicine.

Do not take any other medicine unless prescribed by your doctor. Some medicines may increase or decrease the effects of thyroid on your body and cause problems in controlling your condition. Also, thyroid hormones may change the effects of other medicines.


Side Effects of This Medicine

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur since they may indicate an overdose or an allergic reaction:

For patients taking this medicine for underactive thyroid:

Other effects may occur if the dose of the medicine is not exactly right. These side effects will go away when the dose is corrected. Check with your doctor if any of the following symptoms occur:


Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.


Revised: 06/21/2000

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