THYROIDHORMONES (Systemic)
Some commonly used brand names are:
In the U.S.?
- Armour Thyroid 5
- Cytomel 2
- Levo-T 1
- Levothroid 1
- Levoxyl 1
- Synthroid 1
- Thyrar 5
- Thyroid Strong 5
- Thyrolar 3
- Triostat 2
- Westhroid 5
In Canada?
- Cytomel 2
- Eltroxin 1
- PMS-Levothyroxine Sodium 1
- Synthroid 1
Note: | For quick reference, the following thyroid hormones are numberedto match the corresponding brand names. |
Category
- Antineoplastic?Levothyroxine; Liothyronine; Liotrix; Thyroglobulin; Thyroid
- Diagnostic aid, thyroid function?Levothyroxine; Liothyronine
- Thyroid hormone?Levothyroxine; Liothyronine; Liotrix; Thyroglobulin; Thyroid
Description
Thyroid medicines belong to the general groupof medicines called hormones. They are used when the thyroid gland does notproduce enough hormone. They are also used to help decrease the size of enlargedthyroid glands (known as goiter) and to treat thyroid cancer.
These medicines are available only with your doctor's prescription, inthe following dosage forms:
Oral- Levothyroxine
- Tablets (U.S. and Canada)
- Liothyronine
- Tablets (U.S. and Canada)
- Liotrix
- Thyroglobulin
- Thyroid
- Tablets (U.S. and Canada)
Parenteral- Levothyroxine
- Injection (U.S. and Canada)
- Liothyronine
Before Using This Medicine
In deciding to use a medicine, the risks of taking the medicine must beweighed against the good it will do. This is a decision you and your doctorwill make. For thyroid hormones, the following should be considered:
Allergies?Tell your doctor if you have ever had any unusual orallergic reaction to thyroid hormones. Also tell your health care professionalif you are allergic to any other substances, such as foods, preservatives,or dyes.
Pregnancy?Use of proper amounts of thyroid hormone during pregnancyhas not been shown to cause birth defects or other problems. However, yourdoctor may want you to change your dose while you are pregnant. This willmake regular visits to your doctor important.
Breast-feeding?Use of proper amounts of thyroid hormones by mothershas not been shown to cause problems in nursing babies.
Children?Thyroid hormones have been tested in children andhave not been shown to cause different side effects or problems in childrenthan they do in adults.
Older adults?This medicine has been tested and has not been shownto cause different side effects or problems in older people than it does inyounger 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?Althoughcertain medicines should not be used together at all, in other cases two differentmedicines may be used together even if an interaction might occur. In thesecases, your doctor may want to change the dose, or other precautions may benecessary. When you are taking thyroid hormones, it is especially importantthat your health care professional know if you are taking any of the following:
- Anticoagulants (blood thinners)
- Appetite suppressants (diet pills)
- Cholestyramine (e.g., Questran)
- Colestipol (e.g., Colestid)
- Medicine for asthma or other breathing problems
- Medicine for colds, sinus problems, or hay fever or other allergies(including nose drops or sprays)
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:
- Hardening of the arteries
- Overactive thyroid (history of)
- Underactive adrenal gland
- Underactive pituitary gland
Proper Use of This Medicine
Use this medicine only as directedby your doctor. Do not use more or less of it, and do not use it moreoften than your doctor ordered. Your doctor has prescribed the exact amountyour body needs and if you take different amounts, you may experience symptomsof an overactive or underactive thyroid. Take it at the same time each dayto make sure it always has the same effect.
If your condition is due to a lack of thyroid hormone, you may have totake this medicine for the rest of your life. It is very important that you do not stop taking this medicine without first checkingwith your doctor.
Dosing?The dose ofthese medicines will be different for different patients. Follow your doctor's orders or the directions on the label. The followinginformation includes only the average doses of these medicines. If your dose is different, do not change it unless your doctor tellsyou 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 theresults of your thyroid tests. However, treatment is usually started withlower doses that are increased a little at a time until you are taking thefull amount. This helps prevent side effects.
For levothyroxine- For oral dosage form (tablets):
- For replacing the thyroid hormone:
- Adults and teenagers?At first, 0.0125 to 0.05 milligrams (mg)once a day. Then, your doctor may increase your dose a little at a time to0.075 to 0.125 mg a day. The dose is usually no higher than 0.15 mg once aday.
- Children less than 6 months of age?The dose is based on bodyweight and must be determined by your doctor. The usual dose is 0.025 to 0.05mg once a day.
- Children 6 months to 12 months of age?The dose is based onbody weight and must be determined by your doctor. The usual dose is 0.05to 0.075 mg once a day.
- Children 1 to 5 years of age?The dose is based on body weightand must be determined by your doctor. The usual dose is 0.075 to 0.1 mg oncea day.
- Children 6 to 10 years of age?The dose is based on body weightand must be determined by your doctor. The usual dose is 0.1 to 0.15 mg oncea day.
- Children over 10 years of age?The dose is based on body weightand must be determined by your doctor. The usual dose is 0.15 to 0.2 mg oncea day.
- For injection dosage form:
- For replacing the thyroid hormone:
- Adults and teenagers?50 to 100 micrograms (mcg) injected intoa muscle or into a vein once a day. People with very serious conditions causedby too little thyroid hormone may need higher doses.
- Children less than 6 months of age?The dose is based on bodyweight and must be determined by your doctor. The usual dose is 0.019 to 0.038mg once a day.
- Children 6 months to 12 months of age?The dose is based onbody weight and must be determined by your doctor. The usual dose is 0.038to 0.056 mg once a day.
- Children 1 to 5 years of age?The dose is based on body weightand must be determined by your doctor. The usual dose is 0.056 to 0.075 mgonce a day.
- Children 6 to 10 years of age?The dose is based on body weightand must be determined by your doctor. The usual dose is 0.075 to 0.113 mgonce a day.
- Children over 10 years of age?The dose is based on body weightand must be determined by your doctor. The usual dose is 0.113 to 0.15 mgonce a day.
For liothyronine sodium- For oral dosage form (tablets):
- For replacing the thyroid hormone:
- Adults and teenagers?At first, 25 micrograms (mcg) a day. Somepatients with very serious conditions caused by too little thyroid hormonemay need to take only 2.5 to 5 mcg a day at first. Also, some patients withheart disease or the elderly may need lower doses at first. Then, your doctormay increase your dose a little at a time to up to 50 mcg a day if needed.Your doctor may want you to divide your dose into smaller amounts that aretaken two or more times a day.
- For treating a large thyroid gland (goiter):
- Adults?At first, 5 mcg a day. Some patients with heart diseaseor the elderly may need lower doses at first. Then, your doctor may increaseyour dose a little at a time to 50 to 100 mcg a day.
- For injection dosage form:
- For replacing the thyroid hormone in very serious conditions (myxedemacoma):
- Adults?At first, 10 to 50 mcg injected into a vein every fourto twelve hours. Then, your doctor may want to adjust your dose dependingon your condition.
- Children?Use and dose must be determined by your doctor.
For liotrix (levothyroxine and liothyronine combination)- For oral dosage form (tablets):
- For replacing the thyroid hormone:
- Adults, teenagers, and children?At first, 50 micrograms (mcg)of levothyroxine and 12.5 mcg of liothyronine once a day. Some people withvery serious conditions caused by too little thyroid hormone may need only12.5 mcg of levothyroxine and 3.1 mcg of liothyronine once a day. Also, someelderly patients may need lower doses at first. Then, your doctor may wantto increase your dose a little at a time to up to 100 mcg of levothyroxineand 25 mcg of liothyronine.
For thyroglobulin- For oral dosage form (tablets):
- For replacing the thyroid hormone:
- Adults, teenagers, and children?At first, 32 milligrams (mg)a day. Some people with very serious conditions caused by too little thyroidhormone may need to take only 16 to 32 mg a day at first. Then, the doctormay want you to increase your dose a little at a time to 65 to 160 mg a day.
For thyroid- For oral dosage form (tablets):
- For replacing thyroid hormone:
- Adults, teenagers, and children?60 milligrams (mg) a day. Somepeople with very serious conditions caused by too little thyroid hormone mayneed to take only 15 mg a day at first. Also, some elderly patients may needlower doses at first. Then, your doctor may want you to increase your dosea little at a time to 60 to 120 mg a day.
Missed dose?If you miss a dose of this medicine, take it assoon as possible. However, if it is almost time for your next dose, skip themissed 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:
- Keep out of the reach of children.
- Store away from heat and direct light.
- Do not store in the bathroom, near the kitchen sink, or in otherdamp places. Heat or moisture may cause the medicine to break down.
- Do not keep outdated medicine or medicine no longer needed. Be surethat any discarded medicine is out of the reach of children.
Precautions While Using This Medicine
It is very important that yourdoctor check your progress at regular visits, to make sure that thismedicine is working properly.
If you have certain kinds of heart disease, this medicine may cause chestpain or shortness of breath when you exert yourself. If these occur, do notoverdo exercise or physical work. If you have any questions about this, checkwith your doctor.
Before having any kind of surgery (including dental surgery) or emergencytreatment, tell the medical doctor or dentist in chargethat you are taking this medicine.
Do not take any other medicine unless prescribed by your doctor. Some medicinesmay increase or decrease the effects of thyroid on your body and cause problemsin controlling your condition. Also, thyroid hormones may change the effectsof other medicines.
Side Effects of This Medicine
Along with its needed effects, a medicinemay cause some unwanted effects. Although not all of these side effects mayoccur, if they do occur they may need medical attention.
Check with your doctor as soon as possibleif any of the following side effects occur since they may indicate an overdoseor an allergic reaction:
Signs and symptoms of overdose
Chest pain; confusion; fast or irregular heartbeat; mood swings; muscle weakness; psychosis; restlessness (extreme); yellow eyes or skin; shortness of breath
For patientstaking this medicine for underactive thyroid:
- This medicine usually takes several weeks to have a noticeable effecton your condition. Until it begins to work, you may experience no change inyour symptoms. Check with your doctor if the following symptoms continue:
Clumsiness; coldness; constipation; dry, puffy skin; listlessness; muscle aches; sleepiness; tiredness; weakness; weight gain
Other effects may occur ifthe dose of the medicine is not exactly right. These side effects will goaway when the dose is corrected. Check with your doctor if any of the followingsymptoms occur:
Changes in appetite; changes in menstrualperiods; diarrhea; fever; hand tremors; headache; increased sensitivity to heat; irritability; leg cramps; nervousness; sweating; trouble in sleeping; vomiting; weight loss
Other side effects not listedabove may also occur in some patients. If you notice any other effects, checkwith your doctor.
Revised: 06/21/2000
