Levotiroksin sodium enhances the effect of indirect anticoagulants (coumarin derivatives), displacing them from the binding sites with plasma proteins. With simultaneous application, regular monitoring of blood coagulation parameters is necessary.
If necessary, the dose of anticoagulant should be adjusted.
Absorption of levothyroxine sodium may decrease in the case of simultaneous use with aluminum-containing antacid drugs, iron-containing drugs, calcium carbonate. Therefore, taking levothyroxine sodium is recommended at least 2 hours before use.
Sevelamer and lanthanum carbonate can reduce the bioavailability of levothyroxine sodium, in connection with this levothyroxine sodium should be taken at least two hours before their application. It has been reported that very rare cases of hypothyroidism develop with their simultaneous use with levothyroxine sodium.In case of the need for simultaneous use, it is recommended to carefully monitor the concentration of TSH.
The simultaneous use of tricyclic antidepressants with levothyroxine sodium can lead to an increase in the effect of antidepressants.
Thyroid hormones can increase the need for insulin and oral hypoglycemic drugs. More frequent monitoring of the concentration of glucose in the blood plasma is recommended to be performed during the start of the use of levothyroxine sodium, as well as with a change in the daily dose of the drug.
Levotiroksin sodium reduces the action of cardiac glycosides.
Simultaneous application with ion-exchange resins (colestramine, colestipol), as well as calcium and sodium salts of polystyrene-sulfonic acid reduces the concentration of sodium levothyroxine in the blood plasma due to inhibition of its absorption in the intestine. Concerning levothyroxine sodium should be taken 4-5 hours before taking these drugs.
Inhibitors of tyrosine kinase (eg, imatinib, sunitinib) may decrease the efficacy of levothyroxine sodium.Therefore, at the beginning or at the end of the course of simultaneous application, it is recommended to monitor the function of the thyroid gland. If necessary, the dose of levothyroxine sodium is adjusted.
When used simultaneously with anabolic steroids, asparaginase, tamoxifen, pharmacokinetic interaction at the level of binding to plasma proteins is possible.
Salicylates, dicoumarol, furosemide in high doses (250 mg), clofibrate, phenytoin and other drugs are able to displace levothyroxine sodium from the connection with blood plasma proteins, which can lead to an increase in the concentration of the free T4 fraction.
Somatropin, when used concomitantly with levothyroxine sodium, can accelerate the closure of epiphyseal growth zones.
The simultaneous use of barbiturates and other drugs capable of inducing the activity of "hepatic" enzymes (carbamazepine and rifampicin), can lead to an increase in the clearance of levothyroxine sodium, which may require an increase in the daily dose of the drug.
In women who simultaneously use estrogen-containing contraceptives; in postmenopausal women undergoing hormone replacement therapy, the need for levothyroxine sodium may increase.
Propylthiouracil, glucocorticosteroids, beta-adrenoblockers with simultaneous application with levothyroxine sodium inhibit the conversion of T4 to T3.
Simultaneous use of amiodarone and iodine-containing contrast agents, due to high iodine content, may be accompanied by the development of both hyperthyroidism and hypothyroidism.
Particular attention should be paid to patients with nodular goiter with possible development of unrecognized functional autonomy of the thyroid gland. It may be necessary to adjust the dose of levothyroxine sodium.
Sertralin, chloroquine / proguanil reduce the effectiveness of levothyroxine sodium and increase the concentration of TSH in the blood plasma.
Protease inhibitors (eg, ritonavir, lopinavir) can lead to a decrease in the efficacy of levothyroxine sodium. With the simultaneous use of regular monitoring of the concentration of thyroid hormones in the blood plasma is recommended.
With the use of levothyroxine sodium in children with congenital hypothyroidism and the simultaneous consumption of foods containing soy, there was an increase in the concentration of TSH in the blood plasma. In this case, higher doses of levothyroxine sodium may be required to achieve normal concentrations of TSH and T4.Therefore, when eating foods containing soy, and after stopping their use, regular monitoring of the concentration of TSH and T4 in the blood plasma is necessary for possible correction of the daily dose of the drug.