Synthroid

Synthroid treats hypothyroidism and is also used in the treatment of certain types of thyroid cancer. It is best taken on an empty stomach, 30 to 60 minutes before breakfast.

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Synthroid Overview

Reviewed: December 12, 2012
Updated: 

Synthroid is a prescription medication used to treat underactive thyroid gland function (hypothyroidism) as well as to supress pituitary gland function in the treatment of certain types of thyroid cancer.

Synthroid belongs to a group of drugs called synthetic thyroid hormones. These drugs work by raising reduced levels of natural thyroid hormone in the body.

This medication comes in tablet form and is usually taken once daily in the morning, on an empty stomach, 30 to 60 minutes before breakfast with a glass of water.

Common side effects include nervousness, change in appetite, and irregular heartbeats.

 

 

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Synthroid Cautionary Labels

precautionsprecautionsprecautionsprecautionsprecautionsprecautionsprecautions

Uses of Synthroid

Synthroid is a prescription medication used to treat underactive thyroid gland function (hypothyroidism) as well as to supress pituitary gland function in the treatment of certain types of thyroid cancer.

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Manufacturer

Synthroid Drug Class

Synthroid is part of the drug class:

Side Effects of Synthroid

Serious side effects have been reported with Synthroid. See the “Synthroid Precautions” section.

Common side effects of Synthroid include the following:

  • change in appetite
  • weight loss
  • vomiting
  • diarrhea
  • excessive sweating
  • heat intolerance
  • fever
  • changes in menstrual periods
  • rapid or irregular heartbeat or pulse
  • difficulty breathing
  • leg cramps
  • headache
  • nervousness
  • irritability
  • sleeplessness

This is not a complete list of Synthroid side effects. Ask your doctor or pharmacist for more information.

Tell your doctor if you have any side effect that bothers you or that does not go away.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Synthroid Interactions

Tell your doctor about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

  • Antacids
  • Antidepressants
  • Calcium
  • Certain medications to treat seizure disorders, such as:
    • Carbamazepine (Carbatrol, Epitol, Equetro, Tegretol)
    • Phenobarbital (Luminal)
    • Phenytoin (Dilantin, Phenytek) 
  • Cholestyramine (Prevalite, Questran, Questran Light)
  • Colestipol (Colestid)
  • Certain medications to treat diabetes
  • Digoxin (Digitek, Lanoxin)
  • Estrogens, such as birth control pills, patches, rings or hormone replacement therapy
  • Iron
  • Orlistat (Alli, Xenical)
  • Raloxifene (Evista)
  • Rifampin (Rifadin)
  • Sucralfate (Carafate)
  • Theophylline (Uniphyl, Theocron, TheoCap, Theo-24, Elixophyllin)
  • Warfarin (Coumadin, Jantoven)

This is not a complete list of Synthroid drug interactions. Ask your doctor or pharmacist for more information.

Synthroid Precautions

Serious side effects have been reported with Synthroid including the following:

Hair loss. Partial hair loss may occur during the first few months of Synthroid therapy, but this is usually temporary. Consult with your physician if hair loss persists longer than the first few months of treatment.

Reduced Synthroid absorption. Iron and calcium supplements and antacids can decrease the absorption of Synthroid. Synthroid should not be administered within 4 hrs of these products.

Osteoporosis. Synthroid may increase your risk of developing osteoporosis, especially if your dose is too high. Consult with your physician about your individual level of risk for developing osteoporosis while taking Synthroid.

Heart disease. If you have heart disease, your risk for complications of heart disease may increase if you take Synthroid. Consult with your physician about your risk for complications of heart disease before beginning treatment with Synthroid.

Reduced effectiveness of diabetic medications. If you have diabetes, the doses of your diabetic medications may need to be adjusted while you take Synthroid. Consult with your physician about your diabetic medications before beginning treatment with Synthroid.

Do not take Synthroid if you:

  • are allergic to Synthroid or to any of its ingredients
  • have hyperthyroidism (overactive thyroid)
  • have or suspect you have undiagnosed thyroid disease
  • have or suspect you have untreated adrenal insufficiency
  • are or suspect you might be having a heart attack

Synthroid should not be used as a weight loss medication in people without hypothyroidism.

Synthroid Food Interactions

Medicines can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of Synthroid there are no specific foods that you must exclude from your diet when receiving Synthroid.

Inform MD

Before taking Synthroid, tell your doctor about all of your medical conditions. Especially tell your doctor if you:

  • are allergic to Synthroid or to any of its ingredients
  • are pregnant or plan to become pregnant
  • are breastfeeding or plan to breastfeed
  • have heart disease
  • have diabetes
  • have any blood clotting disorders
  • have any adrenal gland problems
  • have any pituitary gland problems
  • have diabetes

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Synthroid and Pregnancy

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Synthroid falls into category A. When pregnant women used Synthroid, their babies did not show any problems related to this medication.

Pregnant women often require higher doses of Synthroid. Tell your doctor if you become pregnant while taking Synthroid. It is likely that your dose of Synthroid will need to be increased while you are pregnant.

Synthroid and Lactation

Tell your doctor if you are breastfeeding or plan to breastfeed.

Synthroid has been detected in human breast milk. Because of the possibility for adverse reactions in nursing infants from Synthroid, a choice should be made whether to stop nursing or to stop use of this medication. The importance of the drug to the mother should be considered.

Synthroid Usage

Take Synthroid exactly as prescribed.

  • Synthroid comes in tablet form and is usually taken by mouth, once daily, with a full glass of water. 
  • Take Synthroid in the morning on an empty stomach, at least one-half hour to one hour before eating any food.
  • Iron and calcium supplements and antacids can decrease the absorption of Synthroid tablets. Take these products at least 4 hours before or 4 hours after you take Synthroid.
  • If necessary, Synthroid tablets can be crushed and mixed in 1 to 2 teaspoons of plain water. This mixture must be taken right away.

It may take several weeks before you notice an improvement in your symptoms. Consult with your physician if you notice no change in your symptoms after four weeks of treatment with Synthroid.

If you forget a dose of Synthroid, take the missed dose as soon as you remember it. If it is almost time for your next dose, skip the missed dose. Do not take two doses of Synthroid at the same time.

Synthroid Dosage

Take this medication exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.

The dose your doctor recommends may be based on the following:

  • the condition being treated
  • other medical conditions you have
  • other medications you are taking
  • how you respond to this medication
  • your weight
  • your age
  • your gender

The recommended dose of Synthroid for the treatment of hypothyroidism is 1.7 mcg (micrograms) per kilogram of body weight taken by mouth once per day. Additional dosing is as follows:

Patients over 50 years of age or under 50 years of age with heart disease: 25 - 50 mcg per day

Patients over 50 years of age with heart disease: 12.5 - 25 mcg per day 

Synthroid Overdose

If you take too much Synthroid, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.

Other Requirements

  • Store at 25°C (77°F)
  • Keep away from heat, moisture, and light
  • Keep this and all medicines out of the reach of children

Synthroid FDA Warning

Thyroid hormones, including Synthroid, either taken alone or along with other therapeutic agents, should not be used for the treatment of obesity or weight loss.

In people with normal levels of thyroid hormone, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life threatening side effects, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects.