What is Cytomel and how is it used?
Cytomel is a prescription medicine used to treat the symptoms of low thyroid hormone (Hypothyroidism), and enlarged thyroid gland (nontoxic goiter), Myxedema and Myxedema Coma. Cytomel may be used alone or with other medications.
Cytomel belongs to a class of drugs called Thyroid Products.
What are the possible side effects of Cytomel?
Cytomel may cause serious side effects including:
- headache,
- irritability,
- trouble sleeping,
- nervousness,
- increased sweating,
- heat intolerance,
- diarrhea, and
- menstrual changes
Get medical help right away, if you have any of the symptoms listed above.
The most common side effects of Cytomel include:
- nausea
Tell the doctor if you have any side effect that bothers you or that does not go away.
These are not all the possible side effects of Cytomel. For more information, ask your doctor or pharmacist.
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
DESCRIPTION
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.
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.
Cytomel (liothyronine sodium) Tablets contain liothyronine (L-triiodothyronine or LT3), a synthetic form of a natural thyroid hormone, and is available as the sodium salt.
The structural and empirical formulas and molecular weight of liothyronine sodium are given below.
Liothyronine Sodium
L-Tyrosine, O-(4-hydroxy-3-iodophenyl)-3,5-diiodo-, monosodium salt
Twenty-five mcg of liothyronine is equivalent to approximately 1 grain of desiccated thyroid or thyroglobulin and 0.1 mg of L-thyroxine.
Each round, white to off-white Cytomel (liothyronine sodium) tablet contains liothyronine sodium equivalent to liothyronine as follows: 5 mcg debossed KPI and 115; 25 mcg scored and debossed KPI and 116; 50 mcg scored and debossed KPI and 117. Inactive ingredients consist of calcium sulfate, gelatin, corn starch, stearic acid, sucrose and talc.
INDICATIONS
Thyroid hormone drugs are indicated:
As replacement or supplemental therapy in patients with hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. This category includes cretinism, myxedema and ordinary hypothyroidism in patients of any age (pediatric patients, adults, the elderly), or state (including pregnancy); primary hypothyroidism resulting from functional deficiency, primary atrophy, partial or total absence of thyroid gland, or the effects of surgery, radiation, or drugs, with or without the presence of goiter; and secondary (pituitary) or tertiary (hypothalamic) hypothyroidism.
As pituitary thyroid-stimulating hormone (TSH) suppressants, in the treatment or prevention of various types of euthyroid goiters, including thyroid nodules, subacute or chronic lymphocytic thyroiditis (Hashimoto’s) and multinodular goiter.
As diagnostic agents in suppression tests to differentiate suspected mild hyperthyroidism or thyroid gland autonomy.
Cytomel (liothyronine sodium) Tablets can be used in patients allergic to desiccated thyroid or thyroid extract derived from pork or beef.
DOSAGE AND ADMINISTRATION
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.
Mild Hypothyroidism
Recommended starting dosage is 25 mcg daily. Daily dosage then may be increased by up to 25 mcg every 1 or 2 weeks. Usual maintenance dose is 25 to75 mcg daily.
The rapid onset and dissipation of action of liothyronine sodium (T3), as compared with levothyroxine sodium (T4), has led some clinicians to prefer its use in patients who might be more susceptible to the untoward effects of thyroid medication. However, the wide swings in serum T levels that follow its administration and the possibility of more pronounced cardiovascular side effects tend to counterbalance the stated advantages.
Cytomel (liothyronine sodium) Tablets may be used in preference to levothyroxine (T4) during radioisotope scanning procedures, since induction of hypothyroidism in those cases is more abrupt and can be of shorter duration. It may also be preferred when impairment of peripheral conversion of T4 to T3 is suspected.
Myxedema
Recommended starting dosage is 5 mcg daily. This may be increased by 5 to 10 mcg daily every 1 or 2 weeks. When 25 mcg daily is reached, dosage may be increased by 5 to 25 mcg every 1 or 2 weeks until a satisfactory therapeutic response is attained. Usual maintenance dose is 50 to 100 mcg daily.
Myxedema Coma
Myxedema coma is usually precipitated in the hypothyroid patient of long standing by intercurrent illness or drugs such as sedatives and anesthetics and should be considered a medical emergency.
An intravenous preparation of liothyronine sodium is recommended for use in myxedema coma/precoma.
Congenital Hypothyroidism
Recommended starting dosage is 5 mcg daily, with a 5 mcg increment every 3 to 4 days until the desired response is achieved. Infants a few months old may require only 20 mcg daily for maintenance. At 1 year, 50 mcg daily may be required. Above 3 years, full adult dosage may be necessary.
Simple (non-toxic) Goiter
Recommended starting dosage is 5 mcg daily. This dosage may be increased by 5 to 10 mcg daily every 1 or 2 weeks. When 25 mcg daily is reached, dosage may be increased every week or two by 12.5 or 25 mcg. Usual maintenance dosage is 75 mcg daily.
In the elderly or in pediatric patients, therapy should be started with 5 mcg daily and increased only by 5 mcg increments at the recommended intervals.
When switching a patient to Cytomel (liothyronine sodium) Tablets from thyroid, L-thyroxine or thyroglobulin, discontinue the other medication, initiate Cytomel at a low dosage, and increase gradually according to the patient’s response. When selecting a starting dosage, bear in mind that this drug has a rapid onset of action, and that residual effects of the other thyroid preparation may persist for the first several weeks of therapy.
Thyroid Supression Therapy
Administration of thyroid hormone in doses higher than those produced physiologically by the gland results in suppression of the production of endogenous hormone. This is the basis for the thyroid suppression test and is used as an aid in the diagnosis of patients with signs of mild hyperthyroidism in whom baseline laboratory tests appear normal or to demonstrate thyroid gland autonomy in patients with Graves’ ophthalmopathy. I uptake is determined before and after the administration of the exogenous hormone. A 50% or greater suppression of uptake indicates a normal thyroid-pituitary axis and thus rules out thyroid gland autonomy.
Cytomel (liothyronine sodium) Tablets are given in doses of 75 to 100 mcg/day for 7 days, and radioactive iodine uptake is determined before and after administration of the hormone. If thyroid function is under normal control, the radioiodine uptake will drop significantly after treatment. Cytomel (liothyronine sodium) Tablets should be administered cautiously to patients in whom there is a strong suspicion of thyroid gland autonomy, in view of the fact that the exogenous hormone effects will be additive to the endogenous source.
HOW SUPPLIED
Cytomel (liothyronine sodium) Tablets: 5 mcg in bottles of 100; 25 mcg in bottles of 100; and 50 mcg in bottles of 100.
5 mcg 100’s: NDC 60793-115-01
25 mcg 100’s: NDC 60793-116-01
50 mcg 100’s: NDC 60793-117-01
Store between 15° and 30°C (59° and 86°F).