Levothyroxine Side Effects

Brand Names: Tirosint, Synthroid, Levoxyl

Please note - some side effects for Levothyroxine 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 Levothyroxine - for the consumer

Levothyroxine

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 Levothyroxine:

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.

Levothyroxine Solution

All medicines may cause side effects, but many people have no, or minor, side effects. When used in small doses, no COMMON side effects have been reported with Levothyroxine Solution. Seek medical attention right away if any of these SEVERE side effects occur when using Levothyroxine Solution:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); change in appetite; chest pain; diarrhea; difficulty sleeping; headache; increased heart rate; increased sensitivity to heat; increased sweating; nervousness; shortness of breath; trembling or shaking hands; weight loss.

For the professional

Levothyroxine

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 epiphyses 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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