Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2019 Publisher: Mercury Pharmaceuticals Ltd, Capital House, 85 King William Street, London EC4N 7BL, UK
Pharmacotherapeutic group: Thyroid hormones
ATC Code: H03AA01
Eltroxin is a tablet containing Levothyroxine sodium used for the treatment of hypothyroidism. The thyroid gland is dependent upon 2 active principles for it’s main hormone activity these are Levothyroxine (tetraiodothyronine) and Tri-iodothyronine (see Goodman and Gilman, 1985). These closely related iodine containing amino acids are incorporated into the glycoprotein thyroglobulin. The chief action of Levothyroxine is to increase the rate of cell metabolism. Levothyroxine is deiodinated in peripheral tissues to form triiodothyronine which is thought to be the active tissue form of thyroid hormone. Triiodothyronine has a rapid action but a shorter duration of activity than Levothyroxine.
The chief action of Levothyroxine is to increase the rate of cell metabolism.
Levothyroxine sodium is incompletely and variably absorbed from the gastrointestinal tract. It is almost completely bound to plasma proteins and has a half-life in the circulation of about a week in healthy subjects, but longer in patients with myxoedema.
A large portion of the Levothyroxine leaving the circulation is taken up by the liver. Part of a dose of Levothyroxine is metabolised to triiodothyronine. Levothyroxine is excreted in the urine as free drug, deiodinated metabolites and conjugates. Some Levothyroxine is excreted in the faeces. There is limited placental transfer of Levothyroxine.
No further data of relevance.
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