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THYROXINE

How does it work?
How do I take it?
What side effects can be expected?
Other medicines or substances which might interfere with your treatment
Storing your medicine
Further information

Available as Thyroxine Tablets in 25 microgram, 50 microgram and 100 microgram strengths. May also supplied under the trade name Eltroxin .

How does it work?

Thyroxine is the main hormone produced by the thyroid gland. It plays an important role in regulating many of the body’s metabolic functions. Hypothyroidism is the condition that results from under-production of thyroxine by the thyroid gland either because the gland is naturally underactive or because radioiodine therapy or surgery for an overactive gland has resulted in underactivity. Thyroxine is taken to replace the deficiency which exists in such situations and therefore to restore normal metabolic activity.

How do I take it?

Thyroxine has a very long action in the body and is taken as a single daily dose, usually in the morning preferably before breakfast. The actual dose may vary from patient to patient since it is requires to be tailored to the individual’s requirement. This is determined by a simple blood test which will allow the Doctor to adjust the dose from time to time as necessary. For most patients, the dose lies in the range from 50 microgram to 200 microgram daily. Note that thyroxine treatment is started at low dosage (as low as 25 microgram daily in older patients and in those with heart conditions such as angina) then increased gradually as required in order to limit the risk of heart rhythm disturbances and chest pain (see below).

What side effects can be expected?

Since thyroxine is a replacement therapy, few side effects should be anticipated providing the dosage is suitably tailored to need. When daily doses exceed what is actually required there is a tendency for increased metabolic activity which may result in palpitations and chest pain (especially in those with heart disease), muscle cramps, sweating, tremors, diarrhoea, restlessness, insomnia and headaches. However such problems, should they occur, will readily respond to a reduction in dosage.

Very occasionally allergic reactions (usually skin rashes) have been reported with tablets from different suppliers. This suggests that something in the tablet, other than thyroxine, may be implicated and a change of brand will generally overcome such problems.

Other medicines or substances which might interfere with your treatment

If thyroxine is started (or if the dose becomes excessive) in a diabetic patient there is likely to be a requirement for increased dosage of insulin or oral anti-diabetic therapy. Similarly the dose of warfarin may require to be reduced in patients who are anticoagulated.

Some anticonvulsants (anti-epileptic medicines) including phenytoin and carbamazepine (Tegretol) may alter the metabolism of thyroxine by the liver. Because of this, the dose of thyroxine may require to be altered if these are started or stopped in a patient controlled on thyroxine. This also applies when carbamazepine (Tegretol) is used in the treatment of some types of nerve pain.

It may be necessary to adjust the dose of thyroxine upwards if the oral contraceptive pill is commenced.

Storing your medicine

Thyroxine tablets should be stored in the container in which they have been dispensed and kept in a cool dry place.

Further information

Further information on Thyroxine in the treatment of thyoid disorders can be obtained from

British Thyroid Foundation

PO Box HP22

Leeds LS6 3RT

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NHS Tayside; 2006; version 1.0

Disclaimer; no liability whatsoever is accepted for information given and all such information, especially with regard to drug usage (UK version provided), must be checked with a person’s health provider.