Article: Levothyroxine

Levothyroxine
Systematic (IUPAC) name
3,5,3',5'-tetraiodo-L-thyronine
Identifiers
CAS number	51-48-9
ATC code	H03AA01
PubChem	853
DrugBank	APRD00235
Chemical data
Formula	C15H10I4NNaO4 * H2O
Mol. weight	798.86 (anhydrous)
Pharmacokinetic data
Bioavailability	~100%
Metabolism	Mainly in liver, kidneys, brains and muscles
Half life	ca. 7 days (in hyperthyroidism 3-4 days, in hypothyroidism 9-10 days)
Excretion	Through faeces and urine
Therapeutic considerations
Pregnancy cat.	A (FDA)
Legal status	℞ Prescription only
Routes	Oral, Intravenous

Levothyroxine Sodium, also known as L-thyroxine, synthetic T4 or simply 3,5,3',5'-tetraiodo-L-thyronine, is a synthetic form of thyroxine (thyroid hormone). As the hormone is chemically in the L-form (instead of D, see chirality), it is metabolised much slower than physiological thyroid hormone, which has a shorter half-life.

The EU has recently standardised the use of the name "levothyroxine" for the drug. Common brand names include "Thyrax", "Euthyrox", "Levaxin" and "Eltroxin" in Europe, and "Levoxyl" and "Synthroid" in the US.

This medicine is usually given to patients with thyroid problems. These many problems can affect the patient's (if he/she is a child/teenager) growth and/or weight.

It is recommended that levothyroxine is taken an hour before meals to maximise its absorption.

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