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Information |
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Drug Groups
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approved |
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Description
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Liotrix is a synthetically derived thyroid hormone replacement preparation. It consists of levothyroxine sodium (thyroxine, T4) and liothyronine sodium (triiodothyronine, T3) in a 4 to 1 ratio by weight. Liotrix was developed when it was believed that serum levels of both T4 and T3 were maintained by direct thyroidal secretion. It is now known that the thyroid gland secretes approximately ten times more T4 than T3 and that 80% of serum T3 is derived from deiodination of T4 in peripheral tissues. Administration of levothyroxine alone is sufficient for maintaining serum T4 and T3 levels in most patients and combination hormone replacement therapy generally offers no therapeutic advantage. In fact, administration of T3 may result in supratherapeutic levels of T3. |
| Indication |
May be used to treat primary, secondary or tertiary hypothyroidism. May also be used to suppress thyroid stimulating hormone (TSH) secretion in patients with simple (nontoxic) goiter, subacute or chronic lymphocytic thyroiditis multinodular goiter, and in the management of thyroid cancer. May be used in conjunction with other antithyroid agents to treat thyrotoxicosis to prevent goitrogenesis and hypothyroidism. May also be used for differential diagnosis of suspected mild hyperthyroidism or thyroid gland autonomy. |
| Pharmacology |
Thyroid hormone drugs are natural or synthetic preparations containing T4 or T3 or both. T4 and T3 are produced in the human thyroid gland by the iodination and coupling of the amino acid tyrosine. Liotrix is a synthetic preparation of T4 and T3 in a 4:1 weight-based ratio. These hormones enhance oxygen consumption by most tissues of the body and increase the basal metabolic rate and the metabolism of carbohydrates, lipids and proteins. Thus, they exert a profound influence on every organ system in the body and are of particular importance in the development of the central nervous system. |
| Toxicity |
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. |
| Affected Organisms |
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Humans and other mammals |
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| Elimination |
Thyroid hormones are primarily eliminated by the kidneys. |
| References |
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Cobb WE, Jackson IM: Drug therapy reviews: management of hypothyroidism. Am J Hosp Pharm. 1978 Jan;35(1):51-8.
[Pubmed]
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