Synthroid

What Is Synthroid?

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.

What Are Side Effects of Synthroid?

Common side effects of Synthroid include:

• fever,
• hot flashes,
• sensitivity to heat,
• sweating,
• headache,
• nervousness,
• irritability,
• nausea,
• sleep problems (insomnia),
• changes in appetite or changes in weight,
• changes in menstrual perdiods,
• and temporary hair loss.

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

Dosage for Synthroid

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.

What Drugs, Substances, or Supplements Interact with Synthroid?

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.

Synthroid During Pregnancy and Breastfeeding

Pregnant and lactating females need to discuss the dose and use of this medication with their caregivers.

Additional Information

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

 

Synthroid Consumer Information

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

Call your doctor at once if you have:

• fast or irregular heartbeats;
• chest pain, pain spreading to your jaw or shoulder;
• shortness of breath;
• fever, hot flashes, sweating;
• tremors, or if you feel unusually cold;
• weakness, tiredness, sleep problems (insomnia);
• memory problems, feeling depressed or irritable;
• headache, leg cramps, muscle aches;
• feeling nervous or irritable;
• dryness of your skin or hair, hair loss;
• irregular menstrual periods; or
• vomiting, diarrhea, appetite changes, weight changes.

Certain side effects may be more likely in older adults.

Common side effects may include:

• chest pain, irregular heartbeats;
• shortness of breath;
• headache, leg cramps, muscle pain or weakness;
• tremors, feeling nervous or irritable, trouble sleeping;
• increased appetite;
• feeling hot;
• weight loss;
• changes in your menstrual periods;
• diarrhea; or
• skin rash, partial 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 SYNTHROID therapy are primarily those of hyperthyroidism due to therapeutic overdosage [see WARNINGS AND PRECAUTIONS, OVERDOSAGE]. 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, muscle spasm
• Cardiovascular: palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest
• Respiratory: dyspnea
• Gastrointestinal: diarrhea, vomiting, abdominal cramps, elevations in liver function tests
• Dermatologic: hair loss, flushing, rash
• Endocrine: decreased bone mineral density
• Reproductive: menstrual irregularities, impaired fertility

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

Adverse Reactions In Children

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.

Hypersensitivity Reactions

Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various gastrointestinal 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)