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50 mcg: Each uncoated tablet contains: Levothyroxine sodium, BP Equivalent to anhydrous levothyroxine sodium 50 mcg.
100 mcg: Each uncoated tablet contains: Levothyroxine sodium, BP Equivalent to anhydrous levothyroxine sodium 100 mcg.

Pharmacology: Pharmacodynamics: Thyroxine (T4) is a naturally occurring hormone produced by the thyroid gland and converted to the more active hormone triiodothyronine (T3) in peripheral tissues. The precise signals controlling the conversion of T4 to T3 within the cell are not known. The thyroid hormones are required for normal growth and development, particularly of the nervous system. They increase the resting or basal metabolic rate of the whole organism and have stimulatory effects on the heart, skeletal muscle, liver and kidney. Thyroid hormones enhance lipolysis and the utilization of carbohydrate.
100 microgram thyroxine is equivalent in activity to 20 to 30 microgram liothyronine/triiodothyronine or 60 mg Thyroid, BP and/or local pharmacopeia specification.
Pharmacokinetics: Absorption: Following oral administration, the absorption of thyroxine is incomplete and variable, especially when taken with food. The amount absorbed increases during fasting conditions.
Distribution: Thyroxine is nearly totally bound to serum protein.
Metabolism: The main pathway for the metabolism of thyroxine (T4) is its conversion, by de-iodination, to the active metabolite triiodothyronine (T3). Further de-iodination of T4 and T3 leads to production of inactive products.
Elimination: Thyroxine is eliminated slowly from the body with a half-life of approximately seven days in a normal person. This may be reduced in hyperthyroid states or increased in hypothyroid patients. In man, approximately 20 to 40% of thyroxine is eliminated in the feces and approximately 30 to 55% of a dose of thyroxine is excreted in the urine.

Levothyroxine is used to treat an under active thyroid (hypothyroidism). It replaces the hormone that is normally produced by the thyroid gland. Low thyroid levels can occur naturally or when the thyroid gland is injured by radiation/medications or removed by surgery. It is important to have adequate levels of thyroid hormone in the bloodstream to maintain normal mental and physical activity. In children, adequate levels of thyroid hormone are important for normal mental and physical growth and development. This medication is used to treat other types of thyroid disorders as well (e.g., certain types of goiters, thyroid nodules, thyroiditis, and thyroid cancer).

Adults: Initially 50-100 mcg increased by 25-50 mcg at 3-4 week intervals to maintain maximum 150-300 mcg daily.
Children: Initially 25-150 mcg with 25 mcg increments every 2-4 weeks. Juvenile myxedema starting dose of children over 1 year may be 2.5 to 5 mcg/kg per day.
It is best to take levothyroxine on an empty stomach, 30 to 60 minutes before breakfast.
If necessary (such as for young children), a levothyroxine tablet may be crushed and mixed with one or two teaspoons of water. This mixture must be taken immediately (it should not be stored).
Try to take levothyroxine at the same time each day to keep an even level of the medication in the blood.

Taking even a little too much levothyroxine can cause an overdose on the medication. A levothyroxine overdose can cause dangerous symptoms, such as confusion, seizures, or strokes. The effects from a levothyroxine overdose will vary depending on how much of the medication was taken and whether it was taken with other substances.

Hypersensitivity to any component of the preparation; Thyrotoxicosis.

This medication should not be used either alone or in combination with diet pills to treat obesity or for weight loss because serious, even life-threatening, effects could occur. Large doses of this medication, especially with diet pills, may cause symptoms of toxicity.

Coronary heart disease, ECG changes of myocardial infarction. In patients with adrenal insufficiency, first corticosteroid therapy should be given followed by thyroxine.

Pregnancy: Thyroid hormone therapy during pregnancy is usually safe but should be supervised by a physician.
Nursing Mothers: Thyroid hormone therapy in nursing mothers is usually safe but should be supervised by a physician.

Palpitation, osteoporosis, angina, tremors, thyrotoxicosis, allergic reaction, headache, tachycardia, diarrhea, restlessness, sweating, loss of weight and muscle weakness.

Levothyroxine sodium increases the effect of anticoagulants and it may be necessary to reduce the dose of anticoagulant if excessive hypoprothrombinemia and bleeding are to be avoided. Phenytoin levels may be increased by levothyroxine sodium.
Anticonvulsants such as carbamazepine and phenytoin enhance the metabolism of thyroid hormones and may displace them from plasma proteins. Initiation or discontinuation of anticonvulsant therapy may alter levothyroxine sodium dose requirements.
If co-administered with cardiac glycosides, adjustment of dosage of cardiac glycoside may be necessary.
The effects of sympathomimetic agents are also enhanced: Levothyroxine sodium increases receptor sensitivity to catecholamines thus accelerating the response to tricyclic antidepressants.
Cholestyramine given concurrently reduces the gastrointestinal absorption of thyroxine. A number of other drugs may decrease absorption of levothyroxine sodium, and hydroxide, bile acid sequestrants (e.g., colestipol), anion/cation exchange resins (e.g., kayexalate, sevelamer), sucralfate, calcium carbonate, and ferrous sulfate.
Co-administration of oral contraceptives, as well as a number of other drugs, including estrogen, tamoxifen, clofibrate, methadone, and 5-fluorouracil may increase serum concentration of thyroxine-binding globulin, and therefore increase levothyroxine sodium dosage requirements.
Reports indicate that some HMG-CoA reductase inhibitors (statins) may increase thyroid hormone requirements in patients receiving thyroxine therapy. It is unknown if this occurs with all statins. Close monitoring of thyroid function and appropriate thyroxine dose adjustments may be necessary when thyroxine and statins are co-prescribed.
A number of drugs may decrease serum concentration of thyroxine-binding globulin, and therefore decrease levothyroxine sodium dosage requirements, including androgens and anabolic steroids.
Treatment with some tyrosine kinase inhibitors (e.g., imatinib and sunitinib) was associated with increased levothyroxine sodium dosage requirements in hypothyroid patients. Treatments with amiodarone has been associated with multiple effects on thyroid function including increased levothyroxine sodium dosage requirements in hypothyroid patients. A number of drugs may affect thyroid function tests and this should be borne in mind when monitoring a patient on levothyroxine sodium therapy.

Store at temperatures not exceeding 30°C.
Protect from light.

Thyroid Hormones

H03AA01 - levothyroxine sodium ; Belongs to the class of thyroid hormones.

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