Thyrolar® Tablets (Liotrix Tablets, USP)

Rx only

Thyrolar Tablets (Liotrix Tablets, USP) contain triiodothyronine (T3 liothyronine) sodium and tetraiodothyronine (T4 levothyroxine) sodium in the amounts uled in the “How Supplied” section. (T3 liothyronine sodium is approximately four times as potent as T4 thyroxine on a microgram for microgram basis.)

The inactive ingredients are calcium phosphate, colloidal silicon dioxide, corn starch, lactose, and magnesium stearate. The tablets also contain the following dyes: Thyrolar 1/4 - FD&C Blue #1 and FD&C Red #40; Thyrolar 1/2 - FD&C Red #40 and D&C Yellow #10; Thyrolar 1 - FD&C Red #40; Thyrolar 2 - FD&C Blue #1, FD&C Red #40, and D&C Yellow #10; Thyrolar 3 - FD&C Red #40 and D&C Yellow #10.

STRUCTURAL FORMULAS

The steps in the synthesis of the thyroid hormones are controlled by thyrotropin (Thyroid Stimulating Hormone, TSH) secreted by the anterior pituitary. This hormone's secretion is in turn controlled by a feedback mechanism effected by the thyroid hormones themselves and by thyrotropin releasing hormone (TRH), a tripeptide of hypothalamic origin. Endogenous thyroid hormone secretion is suppressed when exogenous thyroid hormones are administered to euthyroid individuals in excess of the normal gland's secretion.

The mechanisms by which thyroid hormones exert their physiologic action are not well understood. These hormones enhance oxygen consumption by most tissues of the body, 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.

The normal thyroid gland contains approximately 200 mcg of levothyroxine (T4) per gram of gland, and 15 mcg of triiodothyronine (T3) per gram. The ratio of these two hormones in the circulation does not represent the ratio in the thyroid gland, since about 80 percent of peripheral triiodothyronine comes from monodeiodination of levothyroxine. Peripheral monodeiodination of levothyroxine at the 5 position (inner ring) also results in the formation of reverse triiodothyronine (T3), which is calorigenically inactive.

Triiodothyronine (T3) levels are low in the fetus and newborn, in old age, in chronic caloric deprivation, hepatic cirrhosis, renal failure, surgical stress, and chronic illnesses representing what has been called the “low triiodothyronine syndrome.”

• 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 (children, 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 (See WARNINGS).
• As pituitary TSH suppressants, in the treatment or prevention of various types of euthyroid goiters, including thyroid nodules, sub-acute or chronic Iymphocytic thyroiditis (Hashimoto's), multinodular goiter, and in the management of thyroid cancer.
• As diagnostic agents in suppression tests to differentiate suspected mild hyperthyroidism or thyroid gland autonomy.

Thyroid hormone preparations are generally contraindicated in patients with diagnosed but as yet uncorrected adrenal cortical insufficiency, untreated thyrotoxicosis, and apparent hypersensitivity to any of their active or extraneous constituents. There is no well documented evidence from the literature, however, of true allergic or idiosyncratic reactions to thyroid hormone.

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 use of thyroid hormones in the therapy of obesity, alone or combined with other drugs, is unjustified and has been shown to be ineffective. Neither is their use justified for the treatment of male or female infertility unless this condition is accompanied by hypothyroidism.

During postmarketing surveillance, the following events have been observed to have occured in patients administered Thyrolar: fatigue, sluggishness, increase in weight, alopecia, palpitations, drug skin, urticaria, headache, hyperhidrosis, pruritus, asthenia, increased blood pressure, arthralgia, myalgia, tremor, hypothyroidism, increase in TSH, decrease in TSH, nausea, chest pain, hypersensitivity, keratoconjunctivitis sicca, increased heart rate, irregular heart rate, anxiety, depression, and insomnia.

Adverse reactions other than those indicative of hyperthyroidism because of therapeutic overdosage, either initially or during the maintenance period, are rare (See OVERDOSAGE).

The dosage of Thyrolar Tablets (Liotrix Tablets, USP) is determined by the indication and must in every case be individualized according to patient response and laboratory findings.

Thyroid hormones are given orally. In acute, emergency conditions, injectable sodium levothyroxine may be given intravenously when oral administration is not feasible or desirable, as in the treatment of myxedema coma, or during total parenteral nutrition. Intramuscular administration is not advisable because of reported poor absorption.

Thyrolar Tablets (Liotrix Tablets, USP) are available in five potencies coded as follows:

Supplied in bottles of 100, two-layered compressed tablets.

Tablets should be stored at cold temperature, between 36˚F and 46˚F (2˚C and 8˚C) in a tight, light-resistant container.

Note: (T3 liothyronine sodium is approximately four times as potent as T4 thyroxine on a microgram for microgram basis.)

FOREST PHARMACEUTICALS, INC.
A Subsidiary of Forest Laboratories, Inc.
St. Louis, MO 63045

Rev. 07/04
RMC #1436

„ 2004 Forest Laboratories, Inc.