The signs and symptoms of overdosage are those of hyperthyroidism [see Warnings and Precautions (5.4) and Adverse Reactions (6)]. In addition, confusion and disorientation may occur. Cerebral embolism, seizure, shock, coma, and death have been reported. Symptoms may not necessarily be evident or may not appear until several days after ingestion.
Reduce the liothyronine sodium dose or temporarily discontinued if signs or symptoms of overdosage occur. Initiate appropriate supportive treatment as dictated by the patient’s medical status.
For current information on the management of poisoning or overdosage, contact the National Poison Control Center at 1-800-222-1222 or www.poison.org.
Liothyronine sodium tablets contain the active ingredient, liothyronine (L-triiodothyronine or LT3 ), a synthetic form of a thyroid hormone liothyronine in sodium salt form. It is chemically designated as L-Tyrosine, O -(4-hydroxy-3-iodophenyl)-3,5-diiodo-, monosodium salt. The molecular formula, molecular weight and structural formula of liothyronine sodium are given below.
C15 H11 I3 NNaO4 M.W.672.96
Liothyronine sodium tablets contain liothyronine sodium equivalent to liothyronine in 5 mcg, 25 mcg, and 50 mcg. Inactive ingredients consist of calcium sulfate, corn starch, gelatin, stearic acid, sucrose and talc.
Thyroid hormones exert their physiologic actions through control of DNA transcription and protein synthesis. Triiodothyronine (T3) and L-thyroxine (T4) diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. This hormone nuclear receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins.
The physiological actions of thyroid hormones are produced predominantly by T3, the majority of which (approximately 80%) is derived from T4 by deiodination in peripheral tissues.
The onset of activity of liothyronine sodium occurs within a few hours. Maximum pharmacologic response occurs within 2 or 3 days.
T3 is almost totally absorbed, 95 percent in 4 hours. The hormones contained in the natural preparations are absorbed in a manner similar to the synthetic hormones.
Liothyronine sodium (T3) is not firmly bound to serum protein. The higher affinity of levothyroxine (T4) for both thyroid-binding globulin and thyroid-binding prealbumin as compared to triiodothyronine (T3) partially explains the higher serum levels and longer half-life of the former hormone. Both protein-bound hormones exist in reverse equilibrium with minute amounts of free hormone, the latter accounting for the metabolic activity.
The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately 80% of circulating T3 is derived from peripheral T4 by monodeiodination. The liver is the major site of degradation for both T4 and T3. T3 is further deiodinated to diiodothyronine. Thyroid hormones are also metabolized via conjugation with glucuronides and sulfates and excreted directly into the bile and gut where they undergo enterohepatic recirculation.
Thyroid hormones are primarily eliminated by the kidneys. A portion of the conjugated hormone reaches the colon unchanged and is eliminated in the feces. The biological half-life is about 2-1/2 days.
Animal studies have not been performed to evaluate the carcinogenic potential, mutagenic potential or effects on fertility of liothyronine sodium.
Liothyronine sodium tablets (round, white to off-white) are supplied as follows:
|Strength||Tablet Markings||NDC – bottles of 100|
|5 mcg||Debossed with KPI on one side and 115 on the other side||59762-1206-1|
|25 mcg||Scored on one side and debossed with KPI and 116 on the other side||59762-1207-1|
|50 mcg||Scored on one side and debossed with KPI and 117 on the other side||59762-1208-1|
Store between 15°C and 30°C (59°F and 86°F).
Dosing and Administration
- Instruct patients that liothyronine sodium should only be taken as directed by their healthcare provider.
- Instruct patients to notify their healthcare provider should they become pregnant or breastfeeding or are thinking of becoming pregnant, while taking liothyronine sodium.
- Inform patients that the liothyronine in liothyronine sodium tablets is intended to replace a hormone that is normally produced by the thyroid gland. Generally replacement therapy is to be taken for life.
- Inform patients that liothyronine sodium should not be used as a primary or adjunctive therapy in a weight control program.
- Instruct patients to notify their healthcare provider if they are taking any other medications, including prescription and over-the-counter preparations.
- Instruct patients to notify their healthcare provider of any other medical conditions, particularly heart disease, diabetes, clotting disorders, and adrenal or pituitary gland problems, as the dose of medications used to control these other conditions may need to be adjusted while taking liothyronine sodium. If patents are taking anticoagulants (blood thinners), their clotting status should be checked frequently.
- Instruct patients to notify their physician or dentist if they are taking liothyronine sodium prior to any surgery.
- Instruct patients to notify their healthcare provider if they experience any of the following symptoms: rapid or irregular heartbeat, chest pain, shortness of breath, leg cramps, headache, nervousness, irritability, sleeplessness, tremors, change in appetite, weight gain or loss, vomiting, diarrhea, excessive sweating, heat intolerance, fever, changes in menstrual periods, hives or skin rash, or any other unusual medical event [see Adverse Reactions (6)].
- Inform patients that partial hair loss may occur rarely during the first few months of liothyronine sodium therapy; this is usually temporary [see Adverse Reactions (6)].
This product’s label may have been updated. For current full prescribing information, please visit www.greenstonellc.com
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