Letter

• Antithyroid Agents
• Anticoagulants
• ATC:H03AA01

• (-)-Thyroxine
• 3,3',5,5'-Tetraiodo-L-thyronine
• D-Thyroxine
• Eltroxin
• Euthyrox
• L-Thryoxin
• L-Thyroxine
• Laevothyroxinum
• Laevoxin
• Letter
• Levaxin
• Levo-t
• Levolet
• Levothroid
• Levothyrox
• Levothyroxin
• Levothyroxine Sodium
• Levothyroxine sodium anhydrous
• Levoxine
• Levoxyl
• Novothyrox
• Oroxine
• Synthroid
• Synthroid Sodium
• THX
• Tetraiodothyronine
• Thyratabs
• Thyrax
• Thyreoideum
• Thyro-tabs
• Thyroxevan
• Thyroxin
• Thyroxinal
• Thyroxine iodine
• Unithroid

• No information avaliable

C₁₅H₁₁I₄NO₄

http://www.rxlist.com/cgi/generic/levothy.htm

Letter FDA

Letter MSDS

Chalmers et al., J. Chem. Soc. 1949, 3424

776.87 g/mol

235.5 ^oC

0.105 mg/mL

Solid

4.099

Liquid; Powder for intravenous injection (6 and 10 mL vials containing 0.2 mg or 0.5mg of levothyroxine per vial); Tablet (0.025, 0.05, 0.075, 0.088, 0.1, 0.112, 0.125, 0.137, 0.15, 0.175, 0.2, and 0.3 mg)

For use alone or in combination with antithyroid agents to treat hypothyroidism, goiter, chronic lymphocytic thyroiditis, myxedema coma, and stupor.

Levothyroxine (T4) is a synthetically prepared levo isomer of thyroxine, the major hormone secreted from the thyroid gland. Thyroxine is released from thyroglobulin by proteolysis and secreted into the blood. Thyroxine is peripherally deiodinated to form triiodothyronine which exerts a broad spectrum of stimulatory effects on cell metabolism. Thyroid hormone increases the metabolic rate of cells of all tissues in the body. In the fetus and newborn, thyroid hormone is important for the growth and development of all tissues including bones and the brain. In adults, thyroid hormone helps to maintain brain function, food metabolism, and body temperature, among other effects. The symptoms of thyroid deficiency relieved by levothyroxine include slow speech, lack of energy, weight gain, hair loss, dry thick skin and unusual sensitivity to cold.

Bioavailability varies from 48% to 80%. Human studies have confirmed the importance of an intact jejunum and ileum for levothyroxine absorption and have shown some absorption from the duodenum.

LD₅₀=20 mg/kg (orally in rat). Hypermetabolic state indistinguishable from thyrotoxicosis of endogenous origin. Symptoms of thyrotoxicosis include weight loss, increased appetite, palpitations, nervousness, diarrhea, abdominal cramps, sweating, tachycardia, increased pulse and blood pressure, cardiac arrhythmias, tremors, insomnia, heat intolerance, fever, and menstrual irregularities.

Levothyroxine is a synthetic thyroid hormone used for the treatment of hypothyroidism (low thyroid hormone secretion). Inform your physician if you are pregnant or nursing. Take this medication on an empty stomach at approximately the same time each morning. Do not stop taking levothyroxine without talking with your physician. Do not change from one brand of this medication to another without talking with your pharmacist or physician. Notify your physician if headache, nervousness, diarrhea, excessive sweating, chest pain, increased pulse rate, or palpitations occur.

Humans and other mammals