Novothyral
 

Special warnings and special precautions for use

Before therapy the following diseases should be excluded or treated: coronary insufficiency, pituitary or adrenal cortical insufficiency, thyroid autonomy.
Even slight drug-induced hyperthyroidism must be avoided in patients with coronary failure, cardiac insufficiency or tachycardiac arrhythmias. Hence frequent checks of thyroid hormone parameters must be made in these cases.
In the case of secondary hypothyroidism the cause must be determined before replacement therapy is given and, if necessary, replacement treatment of a compensated adrenal insufficiency must be commenced.
Where thyroid autonomy is suspected a TRH test should be carried out or a suppression scintigram obtained before treatment.


Interactions with other medicaments and other forms of interaction

Antidiabetes:

Thyroid hormones may reduce the hypoglycemic action of antidiabetics. The blood sugar level of diabetic patients is therefore to be checked regularly particularly at the start of treatment. The dosage of the hypoglycemic drug is to be adjusted, if necessary.

Coumarin derivatives:

The effect of an anticoagulant treatment may be potentiated since thyroid hormones may displace anticoagulants from their plasma protein bonds. Therefore, regular checks of the coagulation are required during concomitant treatment. The dosage of the anticoagulant is to be adjusted, if necessary (dose reduction).

Cholestyramine:

Cholestyramine inhibits the absorption of thyroid hormones and should therefore be administered only 4 - 5 hours after intake of thyroid hormones.

Phenytoin:

Rapid i.v. administration of phenytoin may produce increased plasma levels of free levothyroxine as well as liothyronine and in isolated cases may enhance the development of cardiac arrhythmias.

Salicylate, dicumarol, furosemide, clofibrate:

Thyroid hormones may be displaced from the plasma protein bonds by salicylates, dicumarol, high doses of furosemide (250 mg), clofibrate and other substances.


Pregnancy and lactation

Treatment with thyroid hormones should be given consistently particularly during pregnancy. To date there have been no reports of risk to the fetus despite extensive use during pregnancy. Even in high-dosed therapy the thyroid hormone quantity secreted into mother's milk during lactation is not sufficient to cause development of hyperthyroidism or suppression of TSH secretion in the infant. The use of thyroid hormones as concomitant therapy in the treatment of hyperthyroidism with antithyroid drugs is contraindicated. Since the latter - in contrast to thyroid hormones - can pass the placental barrier in effective doses, the concomitant therapy with thyroid hormones necessitates a higher dosage of the antithyroid drug, which could induce hypothyroidism in the fetus. Consequently, in hyperthyroid pregnant women monotherapy with antithyroid drugs in a dose as low as possible should be given.


Effects on ability to drive to to use machines

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


Undesirable effects

Side-effects are not to be expected if the preparation is used as directed and if clinical and laboratory chemical parameters are monitored. If the dose is not tolerated by individual patients or in the case of overdosage the following clinical symptoms may occur which may also be present in the case of hyperthyroidism, especially if the dose is increased too rapidly at the start of treatment: tachycardia, cardiac arrhythmias, states of angina pectoris, tremor, restlessness, insomnia, hyperhidrosis, weight loss, diarrhea. In the event of such reactions the daily dose should be reduced or the medication be 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.


Overdose

After overdosage and intoxications the symptoms typical of a moderate to severe increase in the metabolic rate occur (s. 6. Side-effects). It is recommended to discontinue the medication and monitor the patient. Pronounced beta-sympathomimetic effects can be reduced by beta-receptor blockers. The use of antithyroid drugs is not appropriate since a normal function of the thyroid gland has already been attained. In extreme doses (suicidal attempts) plasmapheresis may be helpful.