Interactions

The lipid-lowering agents colestyramine and colestipol reduce the absorption of levothyroxine and for this reason they should not be used until 4 – 5 hours after taking Euthyrox®. Similarly, aluminum-containing antacids and calcium carbonate, as well as iron-containing drugs reduce the absorption of levothyroxine and should therefore not be taken until two hours after taking Euthyrox® at the earliest. Since levothyroxine is partially converted into liothyronine (T3) in the body, this process should not be restricted by taking propylthiouracil, glucocorticoids, beta-blockers and iodine-containing contrast media.

Amiodarone, which is used to treat cardiac arrhythmia, can cause both hyperthyroidism and hypothyroidism due to its high iodine content. If a rapid injection of phenytoin (for epilepsy) is used, this can increase the blood levels of free levothyroxine and liothyronine and thus in rare cases lead to cardiac arrhythmia (symptom of hyperthyroidism).The following active ingredients can also cause the levothyroxine level in the blood to rise: However, the effect of levothyroxine (Euthyrox®) is reduced by the following drugs: Interactions with drugs must also be taken into account in diabetics, as the blood sugar-lowering effect of antidiabetics can be reduced by levothyroxine (Euthyrox®). For this reason, the blood sugar level must be checked very regularly at the beginning of treatment for hypothyroidism in diabetics and the dosage adjusted accordingly.

Levothyroxine can also influence the effect of anticoagulant drugs such as coumarin derivatives, which can lead to increased anticoagulation. Here, blood clotting under Euthyrox® administration must be carefully controlled.

Salicylates (anti-inflammatory, antipyretic)
Dicumarol (anticoagulant)
Clofibrate (lipid-lowering agent, against increased blood lipid levels)
High doses of Furosemid/Lasix®(dehydrating agent)
Among other things
Sertraline (antidepressant)
Chloroquine/proguanil (malaria treatment)
Babiturate (sleeping pill)
Oestrogen-containing contraceptives/hormone replacement therapy
Soy products

No interactions between Euthyrox® and the pill are known to date. However, due to the wide variety of contraceptive preparations, the gynaecologist should be informed about the use of Euthyrox® before taking the pill for the first time. An overdose of Euthyrox® can lead to cycle irregularities.