Special warnings and special precautions for use

Coronary failure must be treated prior to thyroid hormone therapy. Jodthyrox therapy should be started with a low dose which is then gradually increased at large time intervals.
Even mild factitial hyperthyroidism must be avoided in patients with coronary failure, cardiac insufficiency or tachycardiac arrhythmias. Frequent checks of thyroid hormone parameters must be made in these cases.

Diabetes mellitus:

Since thyroid hormones influence glucose absorption and insulin secretion and sensitivity the blood glucose level must be checked regularly in the initial phase of treatment with Jodthyrox and if any alteration is seen the dosage of the hypoglycemic drug must be adjusted accordingly.

Pituarity and adrenocortical insufficiency:

In hypothyroidism caused by pituitary disease it is necessary to establish whether adrenocortical insufficiency is also present. The latter would then need to be treated before thyroid hormone treatment is commenced.

Autonomy of the thyroid:

Autonomy of the thyroid must be excluded by specific methods of diagnosis before commencement of therapy with Jodthyrox.


Interactions

Cholestyramine:

Ingestion of cholestyramine inhibits the absorption of levothyroxine sodium. Jodthyrox should therefore be taken 4 - 5 hours before cholestyramine administration.

Phenytoin, salicylates, furosemide, clofibrate:

Phenytoin, salicylates, furosemide in high doses (250 mg), clofibrate and other substances may potentiate the effect of levothyroxine.
Intravenous administration of phenytoin may produce increased concentrations of the free thyroid hormones and in isolated cases may enhance the development of cardiac arrhythmias.

Coumarin derivatives:

The effect of drugs which suppress the coagulation of the blood may be potentiated by Jodthyrox. Hence at the start of treatment with Jodthyrox coagulation parameters must be checked regularly and it may be necessary to reduce the dose of the anticoagulant.

Antidiabetics:

Levothyroxine may alter the daily insulin requirement in diabetics. The blood sugar level in these patients should be checked frequently at the start of treatment with Jodthyrox and after alterations in dose. The dose of the hypoglycemic agent should be adjusted accordingly.


Use in pregnancy and lactation

Treatment with thyroid hormones should be given consistently during pregnancy and breast-feeding in particular. So far there have been no reports of risk to the fetus despite extensive use during pregnancy. Even in high-dosed levothyroxine therapy the thyroid hormone quantity secreted into breast milk during lactation is not sufficient to cause development of hyperthyroidism or suppression of TSH secretion in the infant.


Effects on ability to drive to to use machines

There are no indications that levothyroxine interferes with driving a vehicle, operating machinery, or working without a firm hold..


Side effects

In patients hypersensitive to iodine ingestion of Jodthyrox can cause fever, skin rash and reddening, pruritus and burning in the eyes, dry cough, diarrhea or headache, in which case treatment with the preparation must be stopped.
As a result of the increased metabolic rate due to levothyroxine tachycardia, cardiac arrhythmias and tremor, restlessness, insomnia, excessive perspiration, weight loss or diarrhea may occasionally occur, in particular at the start of treatment. In the event of such reactions the daily dose should be reduced or the drug discontinued for several days. As soon as the side effect has disappeared treatment may be resumed with a low dose which is then cautiously increased.


Symptoms and treatment of overdosage

After overdosage the symptoms typical of a pronounced increase in the metabolic rate occur.
Depending on the extent of the overdose it is recommended that treatment with the tablets is interrupted and tests carried out. Symptoms consisting of intense beta-sympathomimetic effects such as tachycardia, anxiety, agitation, hyperkinesia, can be reduced by beta-blockers. After extreme doses plasmapheresis may be of help.