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Synthroid

Last reviewed on RxList: 8/31/2016
Synthroid Side Effects Center

Last reviewed on RxList 8/31/2016

Synthroid (levothyroxine sodium) is a synthetic compound identical to T4 (levothyroxine) produced by the human thyroid gland used to treat hypothyroidism due to many causes (for example:

  • thyroid removal,
  • thyroid atrophy,
  • functional T4 deficiency,
  • radiation treatment of the thyroid,
  • and other causes).

Synthroid is also used for pituitary TSH suppression. Synthroid is available in generic form. Common side effects of Synthroid include:

Notify your doctor if you experience serious side effects of Synthroid including rapid heartbeat, fluttering in your chest, or chest pain.

Synthroid is prescribed in tablets that range from 25 to 300 mcg in strength and is usually taken once a day with a full glass of water (about 8 ounces) 30 to 60 minutes before breakfast for best adsorption into the body. Children can take the medicine if the tablet is crushed and put into about 1 to 2 teaspoons of water; do not store or delay giving this crushed pill suspension. Doctors often may have to slowly increase the dose; patients should not increase or decrease this medication themselves. Because some preparations of the drug may contain iodine or lactose, patients should tell their doctors about such allergies or reactions to these components. Many drugs can inhibit Synthroid's adsorption by the body; other medications may increase or decrease its effectiveness once it is adsorbed. Providing a complete list of medications to the doctor will help with getting the correct dose established for each individual patient. Pregnant and lactating females need to discuss the dose and use of this medication with their caregivers.

Our Synthroid Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Synthroid Consumer Information

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have a serious side effect such as:

  • headache;
  • sleep problems (insomnia);
  • feeling nervous or irritable;
  • fever, hot flashes, sweating;
  • pounding heartbeats or fluttering in your chest;
  • changes in your menstrual periods; or
  • appetite changes, weight changes.

Less serious side effects may include mild hair loss.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Synthroid (Levothyroxine Sodium)

Synthroid Professional Information

SIDE EFFECTS

Adverse reactions associated with levothyroxine therapy are primarily those of hyperthyroidism due to therapeutic overdosage (see PRECAUTIONS and OVERDOSE). They include the following:

General

fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating;

Central Nervous System

headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia;

Musculoskeletal

tremors, muscle weakness;

Cardiovascular

palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest;

Respiratory

dyspnea;

Gastrointestinal

diarrhea, vomiting, abdominal cramps and elevations in liver function tests;

Dermatologic

hair loss, flushing;

Endocrine

decreased bone mineral density;

Reproductive

menstrual irregularities, impaired fertility.

Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in children receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants and premature closure of the epiphyses in children with resultant compromised adult height.

Seizures have been reported rarely with the institution of levothyroxine therapy.

Inadequate levothyroxine dosage will produce or fail to ameliorate the signs and symptoms of hypothyroidism.

Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various GI symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness and wheezing. Hypersensitivity to levothyroxine itself is not known to occur.

Read the entire FDA prescribing information for Synthroid (Levothyroxine Sodium)

Related Resources for Synthroid

Read the Synthroid User Reviews »

© Synthroid Patient Information is supplied by Cerner Multum, Inc. and Synthroid Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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