THERAPEUTIC INDICATIONS: CYNOMEL * is indicated for the treatment of hypothyroidism when there is diminished or absent thyroid function, caused by antithyroid agents, radiation therapy, primary atrophy, partial or total removal of the gland or functional alterations of the same.
CYNOMEL * is effective in the treatment of hypothyroidism of any etiology. CYNOMEL use * as replacement therapy in simple goiter (nontoxic) produces results in a rapid reduction in the size of the thyroid gland. CYNOMEL * has proved to be useful in some patients unresponsive to other thyroid preparations, probably because it presents an efficient absorption. It can be used in patients allergic to desiccated thyroid or other thyroid extracts pigs or cattle.
CYNOMEL * can be used in the T3 suppression test to differentiate between hyperthyroidism and euthyroidism.
Pharmacokinetics in Humans: CYNOMEL * (liothyronine) is the synthetic form of human thyroid hormone T3, with all the pharmacological activities of the natural substance.
Thyroid hormone has anabolic, promoting protein synthesis and increases metabolism. It has 4 times higher pharmacological potency of levothyroxine (T4).
After oral administration of CYNOMEL *, about 95% absorbed in the gastrointestinal tract and easily reaches the tissues. Intestinal absorption is better than that of levothyroxine.
The maximum activity of liothyronine sodium is rapid and occurs within hours of being ingested. Maximum pharmacologic response occurs within the first 3 days and provides almost immediate clinical response.
Its biological half-life is approximately 1 to 2 days and the effect lasts for more than 72 hours after stopping the drug. The action of the drug is discontinued quickly, allowing immediate adjustments to the dosage and facilitates control of overdose, if this were to occur.
CONTRAINDICATIONS: Thyrotoxicosis, unstable angina, acute myocardial infarction. CYNOMEL * is contraindicated in patients with adrenal insufficiency irreversible, increasing demand for adrenocortical hormones and may cause an acute adrenal crisis.
PRECAUTIONS: CYNOMEL * should be administered with caution in patients with cardiovascular diseases, including hypertension. Any cardiovascular event require a reduction in dose.
Care must be taken in patients with coronary artery disease, since the possibility of cardiac arrhythmias may be greater in patients treated with thyroid hormones.
In patients in whom hypothyroidism secondary to hypopituitarism, probably coexisting adrenal insufficiency.
When this happens, the latter should be corrected by corticosteroid prior to administration of thyroid hormones.
Use in Pregnancy and Lactation: Thyroid hormones do not readily cross the placental barrier. Clinical experience indicates that CYNOMEL * no adverse effects on the fetus when administered during pregnancy. Based on this knowledge, thyroid replacement therapy to hypothyroid women should not be discontinued during pregnancy.
Thyroid hormones are excreted in small amounts in breast milk and its use has not been associated with serious adverse reactions, however, caution should be exercised when thyroid hormones are administered to nursing women.
SIDE EFFECTS: Excessive doses of thyroid hormones can lead to signs and symptoms of hyper-excitability, weight loss, palpitations, arrhythmias, tachycardia, diarrhea, sweating, tremor, headache and heat intolerance. The effects do not occur immediately and the symptoms may appear 1 to 2 weeks after the initial dose.
The medication in these cases should be discontinued until the symptoms disappear, to restart one or two days later with a smaller dose.
DRUG INTERACTIONS AND OTHER GENDER: Administration of CYNOMEL * can produce drug interactions with various drugs. Increases the anticoagulant effects of warfarin and acenocoumarol. May cause increased requirements for insulin or oral hypoglycemic agents in diabetic patients. Cholestyramine hinders the absorption of thyroid hormones. The use of estrogen or estrogen oral contraceptives may decrease the free levothyroxine and thereby increase thyroid hormone requirements. The use of thyroid hormones with imipramine and other tricyclic antidepressants may increase the antidepressant activity, as well as the activity of thyroid hormones.
Thyroid hormones may potentiate the toxic effects of digitalis, also thyroid replacement therapy increases the metabolic rate, which may require increased doses of digitalis. It has been reported that concomitant administration of thyroid hormones and ketamine, can cause hypertension and tachycardia. Thyroid hormones increase the adrenergic effect of catecholamines such as epinephrine and norepinephrine.
CHANGES IN RESULTS OF LABORATORY TESTS: During thyroid replacement therapy, protein iodine levels generally remain low. As with all thyroid preparations, the operation of the thyroid gland, reflected by the I131 can be depressed by CYNOMEL *, particularly when the dose exceeds 75 mg daily; this effect disappears rapidly and can be obtained within I131 useful values in the weeks after cessation of drug administration.
PRECAUTIONS IN RELATION TO EFFECTS OF CARCINOGENESIS, MUTAGENESIS, Impairment of Fertility: No studies have been conducted in animals over time to evaluate the potential carcinogenic, mutagenic, teratogenic or effects on fertility.
DOSAGE AND ADMINISTRATION: Oral.
CYNOMEL * is generally administered as a single dose, preferably before breakfast.
In moderate hypothyroidism and reproductive disorders caused by hypothyroidism, the recommended starting dose is one tablet daily. The dosage should be adjusted according to response, with gradual increments of half to one tablet daily every 1 to 2 weeks. The usual maintenance dose is one to three tablets daily.
When therapy is discontinued based thyroid thyroid extract, L-thyroxine or thyroglobulin, and started treatment with CYNOMEL *, therapy can be started at low doses and gradually increased according to patient response. When selecting an initial dose, take note that CYNOMEL * acts almost immediately and that the residual effects of the other thyroid preparation may persist several weeks after being administered. Similarly, although CYNOMEL * can quickly suspended, its metabolic effects persist for 72 hours.
Special instructions for T3 suppression test: When the absorption of I131 pretty high levels, administer 3 to 4 tablets of CYNOMEL * daily for 7 days, repeat the test after ingestion of I131. In hyperthyroid patients, ingestion of 131 I for 24 hours, will not be affected significantly. In euthyroid, I131 absorption drops to less than 20%.
REPRESENTATIONS AND MANAGEMENT Overdosage: In case of overdose, symptoms may occur such as headache, irritability, nervousness, excessive sweating, tachycardia, increased bowel motility. It can aggravate the cases of angina pectoris or congestive heart failure and may develop a crash box.
Overdose symptoms may occur over that suggested a thyroid storm, and produce manifestations of hyperthyroidism. In either case should be discontinued for several days and start it again, but with a lower dose. If overdose is acute, avoid the absorption of the drug with the induction of vomiting and gastric lavage. The treatment in cases of shock is supportive care and treatment should be considered for unrecognized adrenal insufficiency. To address the increased sympathetic activity may be included antiadrenergic drugs such as propranolol.