Synthroid Side Effects

Generic Name: Levothyroxine

Please note - some side effects for Synthroid may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA at http://www.fda.gov/medwatch/ or 1-800-FDA-1088 (1-800-332-1088).

Side Effects of Synthroid - for the consumer

Synthroid

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Synthroid:

Anxiety; diarrhea; flushing; mood swings; muscle weakness; partial, temporary hair loss; sleeplessness; stomach cramps; tiredness; vomiting.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); changes in appetite; changes in menstrual periods; chest pain; difficulty breathing; excessive sweating; fast heartbeat; fever; headache; hives or skin rash; hyperactivity; inability to handle warm or hot room/weather conditions; irregular heartbeat; irritability; leg cramps; nervousness; pounding in the chest; seizures; shortness of breath; tremors; weight gain or weight loss.

For the professional

Synthroid

Adverse reactions associated with levothyroxine therapy are primarily those of hyperthyroidism due to therapeutic 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;

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.

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