Liothyronine is a synthetic form of triiodothyronine (T3), a thyroid hormone used to treat hypothyroidism and myxedema coma. T3 is the metabolically active thyroid hormone, which causes feedback inhibition, and lowers elevated TSH levels. It increases metabolism in peripheral tissues and is indicated when there is an impaired conversion of T4 to T3 in peripheral tissues. It is also used as an augmentation strategy in treating major depressive disorder when used in combination with antidepressants.It is marketed as the sodium salt under the brand name Cytomel (or Tertroxin in Australia).
Liothyronine is a thyroid hormone. Thyroid hormone drugs are natural or synthetic preparations containing tetraiodothyronine (T4, levothyroxine) sodium or triiodothyronine (T3, liothyronine) sodium or both. T4 and T3 are produced in the human thyroid gland by the iodination and coupling of the amino acid tyrosine. T4 contains four iodine atoms and is formed by the coupling of two molecules of diiodotyrosine (DIT). T3 contains three atoms of iodine and is formed by the coupling of one molecule of DIT with one molecule of monoiodotyrosine (MIT). Both hormones are stored in the thyroid colloid as thyroglobulin. This medicine can improve symptoms of thyroid deficiency such as slow speech, lack of energy, weight gain, hair loss, dry skin, and feeling cold. It also helps to treat goiter (an enlarged thyroid gland).
Thyroid hormone drugs are natural or synthetic preparations containing tetraiodothyronine (T4, levothyroxine) sodium or triiodothyronine (T3, liothyronine) sodium or both. T4 and T3 are produced in the human thyroid gland by the iodination and coupling of the amino acid tyrosine. T4 contains four iodine atoms and is formed by the coupling of two molecules of diiodotyrosine (DIT). T3 contains three atoms of iodine and is formed by the coupling of one molecule of DIT with one molecule of monoiodotyrosine (MIT). Both hormones are stored in the thyroid colloid as tyroglobulin.
Thyroid hormone preparations belong to two categories: (1) natural hormonal preparations derived from animal thyroid, and (2) synthetic preparations. Natural preparations include desiccated thyroid and thyroglobulin. Desiccated thyroid is derived from domesticated animals that are used for food by man (either beef or hog thyroid), and thyroglobulin is derived from thyroid glands of the hog. The United States Pharmacopeia (USP) has standardized the total iodine content of natural preparations. Thyroid USP contains not less than (NLT) 0.17 percent and not more than (NMT) 0.23 percent iodine, and thyroglobulin contains not less than (NLT) 0.7 percent of organically bound iodine. Iodine content is only an indirect indicator of true hormonal biologic activity.
Liothyronine is used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. It is also used to help decrease the size of enlarged thyroid glands (known as goiter) .Liothyronine is also used in some medical tests to help diagnose problems with the thyroid gland .This medicine is available only with your doctor's prescription .
Physicians may use liothyronine instead of or in addition to levothyroxine (T4) for patients undergoing thyroid hormone withdrawal. When a patient has thyroid cancer or Graves' disease, ablation therapy with radioactive iodine (131I) can be used to remove trace thyroid tissue that may remain after thyroidectomy (surgical excision of the gland). For 131I therapy to be effective, the trace thyroid tissue must be avid to iodine, which is achieved by elevating the patient's TSH levels. For patients taking levothyroxine, TSH may be boosted by discontinuing levothyroxine for 3–6 weeks.This long period of hormone withdrawal is required because of levothyroxine's relatively long biological half-life, and may result in symptoms of hypothyroidism in the patient. The shorter half-life of liothyronine permits a withdrawal period of two weeks, which may minimize hypothyroidism symptoms. One protocol is to discontinue levothyroxine, then prescribe liothyronine while the T4 levels are falling, and finally stop the liothyronine two weeks before the radioactive iodine treatment.
Liothyronine may also be preferred for patients with myxedema coma because of its quicker onset of action when compared to levothyroxine. Low-dose liothyronine has been shown to improve depression symptoms in patients with normal thyroid function who do not have adequate relief from their depression after trying several different antidepressants. When added to existing medications, liothyronine helped achieve remission in 24% of patients participating in a subset of the large STAR*D depression trial.According to a 2001 meta-analysis that analyzed the effectiveness of adding Liothyronine to tricyclic antidepressants, women in particular may benefit from Liothyronine.
The average effective dose for depression was 45 mcg of Liothyronine daily, which is lower than the doses used for treating hypothyroidism. About 9% of patients stopped taking liothyronine due to side effects. The difference in gender response may be due to differences in metabolism of thyroid precursors.
An algorithm developed from the STAR*D trial recommends liothyronine as an option when patients have failed two antidepressant medications.
The dosage of thyroid hormones is determined by the indication and must in every case be individualized according to patient response and laboratory findings.
Cytomel (liothyronine sodium) Tablets are intended for oral administration; once-a-day dosage is recommended. Although liothyronine sodium has a rapid cutoff, its metabolic effects persist for a few days following discontinuance.
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:
-Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Pregnancy Per the U.S. FDA, liothyronine is categorized as Pregnancy Category A.Thyroid hormone is minimally transferred to the fetus or placenta, however as of October 2014, studies have not shown any adverse effects to the fetus. Hypothyroid mothers should continue to take thyroid hormone replacement therapy throughout pregnancy to avoid adverse events.
Nursing Breastmilk contains a low amount of thyroid hormone, so it is important to exercise caution when breastfeeding while taking liothyronine.
Elderly Elderly patients should be started on lower doses of liothyronine. Plasma (T3) concentrations in this population are decreased by 25% to 40%.TSH must be routinely monitored since there is a risk of coronary artery disease, hyperthyroidism and excessive bone loss from inadequate or abnormal thyroid replacement.
The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
Liothyronine is the most potent form of thyroid hormone. As a salt of triiodothyronine (T3), it is chemically similar and pharmacologically equivalent to T3. As such, it acts on the body to increase the basal metabolic rate, affect protein synthesis and increase the body's sensitivity to catecholamines (such as adrenaline) by permissiveness. As monotherapy or in combination therapy with SSRIs, liothyronine may also enhance generation of new neurons in the central nervous system.The thyroid hormones are essential to proper development and differentiation of all cells of the human body. These hormones also regulate protein, fat, and carbohydrate metabolism, affecting how human cells use energetic compounds.
In comparison to levothyroxine (T4), liothyronine has a faster onset of action as well as a shorter biological half-life, which may be due to less plasma protein binding to thyroxine-binding globulin and transthyretin.
For the treatment of mild hypothyroidism:
Adults—At first, 25 micrograms (mcg) once a day. Doses may be increased by up to 25 mcg every 1 or 2 weeks. However, the dose usually is not more than 75 mcg once a day.
Children—Use and dose must be determined by your doctor .
Adults—At first, 5 mcg once a day. Doses may be increased by 5 to 10 mcg daily every 1 or 2 weeks. When the daily dose of 25 mcg is reached, dosage may be increased by 5 to 25 mcg every 1 or 2 weeks as needed. However, the dose usually is not more than 100 mcg once a day.
Children—Use and dose must be determined by your doctor .
Adults and children over 3 years of age—Use and dose must be determined by your doctor.
Children—At first, 5 mcg once a day. Dosage may be increased by 5 mcg every 3 or 4 days as needed.
Children 0 to 1 year of age—20 mcg once a day for maintenance.
Children 1 to 3 years of age—50 mcg once a day .
Adults—At first, 5 mcg once a day. Doses may be increased by 5 to 10 mcg daily every 1 or 2 weeks. When the daily dose of 25 mcg is reached, dosage may be increased by 12.5 to 25 mcg every 1 or 2 weeks as needed. However, the dose usually is not more than 75 mcg once a day.
Children—Use and dose must be determined by your doctor .
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Drugs with thyroid hormone activity, alone or together with other therapeutic agents, have been used for the treatment of obesity. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects.
The following drugs or moieties are known to interfere with laboratory tests performed in patients on thyroid hormone therapy: androgens, corticosteroids, estrogens, oral contraceptives containing estrogens, iodine-containing preparations and the numerous preparations containing salicylates.
Liothyronine may cause a number of side effects, mostly similar to symptoms of hyperthyroidism, which include:
changes in menstrual cycle
sensitivity to heat
It is very important that your doctor check your progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it. Blood and urine tests will be needed to check for unwanted effects .
Liothyronine should not be used for the treatment of obesity or for the purpose of losing weight. This medicine is ineffective for weight reduction and when taken in larger amount, it may cause more serious medical conditions .
Hypothyroidism can sometimes cause infertility in men and women. Liothyronine should not be used for the treatment of infertility unless it is caused by hypothyroidism .
Call your doctor right away if you start to have chest pain, fast or irregular heartbeat, excessive sweating, heat intolerance, nervousness, or any other unusual medical condition .
For patients with diabetes, it is very important that you keep track of your blood or urine sugar levels as instructed by your doctor. Check with your doctor immediately if you notice any changes in your sugar levels .
A temporary loss of hair may occur during the first few months of liothyronine therapy. Ask your doctor about this if you have any concerns
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|White to pale powder|
|4 M NH4OH in methanol: 125 g/5mL, clear, yellow-brown, Partly miscible in water. Soluble in dimethyl sulfoxide, methanol, sodium hydroxide. Practically insoluble in most other organic solvents.|
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