Levoxyl Side Effects

Generic Name: levothyroxine

Please note - some side effects for Levoxyl 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 Levoxyl - for the Consumer

Levoxyl

All medicines may cause side effects, but many people have no, or minor, side effects. No COMMON side effects have been reported with the use of Levoxyl . Seek medical attention right away if any of these SEVERE side effects occur when using Levoxyl:

Severe allergic reactions (rash; hives; itching; difficulty breathing; flushing; tightness in the chest; swelling of the mouth, face, lips, or tongue; unusual hoarseness); changes in appetite; changes in menstrual periods; chest pain; diarrhea; excessive sweating; fast or irregular heartbeat; fever; heat intolerance; joint pain; leg cramps; mental or mood changes (eg, anxiety, irritability, nervousness); muscle weakness; seizures; severe or persistent headache or fatigue; shortness of breath; stomach cramps; tremors; trouble sleeping; unusual weight gain or weight loss; vomiting; wheezing.

Levoxyl Side Effects - for the Professional

Levoxyl

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;

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

Pulmonary: dyspnea;

GI: diarrhea, vomiting, abdominal cramps;

Dermatologic: hair loss, flushing;

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.

In addition to the above events, the following have been reported, predominately when Levoxyl® tablets were not taken with water: choking, gagging, tablet stuck in throat and dysphagia.

Side Effects by Body System

General

Levothyroxine is usually well tolerated. Side effects associated with levothyroxine therapy typically resulted from therapeutic overdosage and included the signs and symptoms of hyperthyroidism. Weight loss, increased appetite, insomnia, anxiety, heat intolerance, diarrhea or increase in bowel frequency, palpitations, hypertension, tachycardia, angina, and menstrual irregularities may be reported. Given the long half-life of levothyroxine, such effects may not be present for several weeks after therapy initiation or dosage increases.

Cardiovascular

Cardiac function was evaluated in twenty patients requiring TSH suppression for either thyroid goiter or following thyroidectomy and radioactive iodine therapy for thyroid cancer and in twenty age- and sex-matched controls. TSH suppression was associated with an increased incidence of premature ventricular beats, an increased left ventricular mass index, and enhanced left ventricular systolic function. The clinical significance of these changes remains to be determined.

A 38-year-old female experienced with severe hypothyroidism experienced myxedema coma and cardiac ischemia coincident with levothyroxine therapy. After 3 months of levothyroxine therapy (initial dose: 12.5 mcg/d; maintenance dose: 125 mcg/d), all abnormal laboratory values associated with hypothyroidism returned to normal. However, three weeks after initiating treatment, the patient reported intermittent chest pains during the course of treatment, and a coronary artery angiogram revealed diffuse stenosis of all 3 branches. She underwent coronary artery bypass grafting, with subsequent improvement in coronary perfusion.

Cardiovascular side effects have included symptoms of palpitations, hypertension, tachycardia, and angina which may be exacerbated in patients with underlying cardiovascular disorders. Ischemic heart disease and significant effects on cardiac function including an increased incidence of premature ventricular beats, an increased left ventricular mass index, and enhanced left ventricular systolic function have been reported in clinical trials.

Endocrine

Endocrine side effects have included changes in symptom presentation for diabetes and adrenal cortical insufficiency.

Nervous system

Nervous system side effects have rarely included seizures during initiation of therapy.

Dermatologic

Dermatologic side effects including transient dermatologic effect and hair loss have been reported during the initial months of therapy.

Musculoskeletal

Musculoskeletal side effects have included an increase risk of osteoporosis. However, data from long-term studies are conflicting.

A study evaluated the effect of long-term thyroid hormone therapy on bone mineral density in 196 women (mean age, 74.4 years) compared to a control group comprised of 795 women (mean age, 72.1 years). The mean daily thyroxine dose was 1.99 mcg/kg (range, 0.3 to 6.6 mcg/kg) with a mean duration of therapy of 20.4 years (range, less than 1 to 68 years). Women taking daily doses of 1.6 mcg/kg or more had significantly lower bone mineral density levels at the ultradistal radius, midshaft radius, hip, and lumbar spine compared to controls. However, estrogen use appeared to negate the adverse effects of thyroid hormone on bone mineral density.

Higher rates of femur fractures have been found in males (p=0.008) prescribed long-term thyroid hormone therapy as compared to controls in a case-control analysis of 23,183 patients, from the United Kingdom General Practice Research Database, prescribed thyroid hormone.

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