Composition

• Each tablet Contains:
• Thyroxine Sodium IP
  50 mcg

Packing

• 1X100
  (Plastic Bottle)

MRP

• 103.04

Overview

Thyroxoine Sodium similar to the hormone produced by the thyroid gland. It is primarily used to treat Hypothyroidism, a condition where the thyroid gland does not produce sufficient quantities of hormones. It is also used to treat certain other disorders associated with the thyroid gland.

Thyroxine sodium is the sodium salt of levothyroxine, a synthetic levisomer of thyroxine (T4) that is similar to the endogenous hormone produced by the thyroid gland. In peripheral tissues, levothyroxine is deiodinated by 5'-deiodinase to form triiodothyronine (T3). T3 enters the cell and binds to nuclear thyroid hormone receptors; the activated hormone-receptor complex in turn triggers gene expression and produces proteins required in the regualtion of cellular respiration;thermogenesis;cellular growth and differentiaton; and the metabolism of proteins,carbohydrates and lipids. T3 also exhibits cardiostimulatory effects.

Indications

Hypothyroidism: As replacement or supplemental therapy in congenital or acquired hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Specific indications include: primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism and subclinical hypothyroidism. Primary hypothyroidism may result from functional deficiency, primary atrophy, partial or total congenital absence of the thyroid gland, or from the effects of surgery, radiation, or drugs, with or without the presence of goiter.

Mechanism of action

Thyroid hormone synthesis and secretion is regulated by the hypothalamic-pituitary-thyroid axis.
Thyrotropin-releasing hormone (TRH) released from the hypothalamus stimulates secretion of thyroid-stimulating hormone, TSH, from the anterior pituitary. The presenvce of TSH stimualtes synthesis and secretion of T4 and L-triidothyronine(T3) by the thyroid. The mechanisms by which thyroid hormones exert their physiologic actions are not completely understood, but it is thought that their principal effects are exerted through control of DNA transcription and protein synthesis. T 3 and 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.

Pharmacodynamics Properties

Pharmacokinetics Properties:

Absorption: Absorption of orally administered T 4 from the gastrointestinal (GI) tract ranges from 40% to 80%. The majority of the thyroxine dose is absorbed from the jejunum and upper ileum. T4 absorption is increased by fasting, and decreased in malabsorption syndromes and by certain foods such as soybean infant formula. Dietary fiber decreases bioavailability of T4 . Absorption may also decrease with age. In addition, many drugs and foods affect T 4 absorption (see PRECAUTIONS , Drug Interactions and Drug-Food Interactions ).
Distribution: Circulating thyroid hormones are greater than 99% bound to plasma proteins, including thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin (TBA), whose capacities and affinities vary for each hormone. The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half-life of T4 compared to T3 . Protein-bound thyroid hormones exist in reverse equilibrium with small amounts of free hormone. Only unbound hormone is metabolically active.
Metabolism: T4 is slowly eliminated. The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately eighty-percent of circulating T3 is derived from peripheral T4 by monodeiodination. The liver is the major site degradation for both T4 and T3, with T4 deiodination also occurring at a number of additional sites, including the kidney and other tissues.
Elimination: Thyroid hormones are primarily eliminated by the kidneys. A portion of the conjugated hormone reaches the colon unchanged and is eliminated in the feces. Approximately 20% of T4 is eliminated in the stool. Urinary excretion of T4 decreases with age.

Side Effects

• Headache
• Diarrhea
• Nervousness and irritability
• Excessive sweating
• Fever
• Nausea and Vomiting
• Abdominal cramps
• Sleeplessnes

Warning & Precaution

Pregnancy: This medicine is safe for use during pregnancy. Consult your doctor before taking this medicine.
Breast-feeding: This medicine is safe for use while breastfeeding. Consult your doctor before taking this medicine.