Thyroid hormones

Levothyroxine Sodium

Approved 24 Jun 2011IntravenousPowder

The FDA lists this product in 60 strengths and forms.

Indications

Levothyroxine Sodium for Injection is indicated for the treatment of myxedema coma. Important Limitations of Use: The relative bioavailability between Levothyroxine Sodium for Injection and oral levothyroxine products has not been established. Caution should be used when switching patients from oral levothyroxine products to Levothyroxine Sodium for Injection as accurate dosing conversion has not been studied. Levothyroxine Sodium is an L-thyroxine product.

Levothyroxine (T 4 ) Sodium for Injection is indicated for the treatment of myxedema coma. ( 1 ) Important Limitations of Use: The relative bioavailability of this drug has not been established. Use caution when converting patients from oral to intravenous levothyroxine. ( 1 )

Contraindications

None. None. ( 4 )

Warnings and precautions

NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS Thyroid hormones, including Levothyroxine Sodium for Injection , should not be used for the treatment of obesity or for weight loss. ( 5.3 ) Larger doses may produce serious or even life threatening manifestations of toxicity. ( 6 ) 5 WARNINGS AND PRECAUTIONS Excessive bolus doses of Levothyroxine Sodium for Injection (> 500 mcg) are associated with cardiac complications, particularly in the elderly and in patients with an underlying cardiac condition.

Initiate therapy with doses at the lower end of the recommended range. ( 5.1 ) Close observation of the patient following the administration of Levothyroxine Sodium for Injection is advised. ( 5.1 ) Levothyroxine Sodium for Injection therapy for patients with previously undiagnosed endocrine disorders, including adrenal insufficiency, hypopituitarism, and diabetes insipidus, may worsen symptoms of these endocrinopathies.

( 5.2 )

5.1Risk of Cardiac Complications in Elderly and in Patients with Cardiovascular Disease

Excessive bolus dosing of Levothyroxine Sodium for Injection (greater than 500 mcg) are associated with cardiac complications, particularly in the elderly and in patients with an underlying cardiac condition. Adverse events that can potentially be related to the administration of large doses of Levothyroxine Sodium for Injection include arrhythmias, tachycardia, myocardial ischemia and infarction, or worsening of congestive heart failure and death.

Indications

Warnings and precautions

( 5.2 )

5.1Risk of Cardiac Complications in Elderly and in Patients with Cardiovascular Disease

Interactions

Many drugs affect thyroid hormone pharmacokinetics and metabolism (e.g., synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to Levothyroxine Sodium for Injection. In addition, thyroid hormones and thyroid status have varied effects on the pharmacokinetics and actions of other drugs (see Section 12.3 ). Many drugs affect thyroid hormone pharmacokinetics and metabolism (e.g., absorption, synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to Levothyroxine Sodium for Injection.

( 7 , 12.3 )

7.1Antidiabetic Therapy Addition

of levothyroxine to antidiabetic or insulin therapy may result in increased antidiabetic agent or insulin requirements. Careful monitoring of diabetic control is recommended, especially when thyroid therapy is started, changed, or discontinued.

7.2Oral Anticoagulants

Levothyroxine increases the response to oral anticoagulant therapy. Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state or when the Levothyroxine Sodium for Injection dose is increased. Prothrombin time should be closely monitored to permit appropriate and timely dosage adjustments.

7.3Digitalis Glycosides

The therapeutic effects of digitalis glycosides may be reduced by levothyroxine. Serum digitalis glycoside levels may be decreased when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides.

7.4Antidepressant Therapy

Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. Toxic effects may include increased risk of cardiac arrhythmias and CNS stimulation; onset of action of tricyclics may be accelerated. Administration of sertraline in patients stabilized on levothyroxine may result in increased levothyroxine requirements.

7.5Ketamine

Concurrent use may produce marked hypertension and tachycardia; cautious administration to patients receiving thyroid hormone therapy is recommended.

7.6Sympathomimetics

Concurrent use may increase the effects of sympathomimetics or thyroid hormone. Thyroid hormones may increase the risk of coronary insufficiency when sympathomimetic agents are administered to patients with coronary artery disease.

7.7Drug-Laboratory Test Interactions Changes

in thyroxine binding globulin (TBG) concentration must be considered when interpreting levothyroxine and triiodothyronine values, which necessitates measurement and evaluation of unbound (free) hormone and/or determination of the free levothyroxine index. Pregnancy, infectious hepatitis, estrogens, estrogen containing oral contraceptives, and acute intermittent porphyria increase TBG concentrations. Decreases in TBG concentrations are observed in nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, and after androgen or corticosteroid therapy.

Familial hyper or hypo thyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9,000.

Levothyroxine Sodium

Indications

Contraindications

Warnings and precautions

5.1Risk of Cardiac Complications in Elderly and in Patients with Cardiovascular Disease

Two medicines in one question?

Levothyroxine Sodium

Indications

Contraindications

Warnings and precautions

5.1Risk of Cardiac Complications in Elderly and in Patients with Cardiovascular Disease

Two medicines in one question?

5.3Not Indicated for Treatment of Obesity

Interactions

7.1Antidiabetic Therapy Addition

7.2Oral Anticoagulants

7.3Digitalis Glycosides

7.4Antidepressant Therapy

7.5Ketamine

7.6Sympathomimetics

7.7Drug-Laboratory Test Interactions Changes

Pregnancy and breastfeeding

8.1Pregnancy Pregnancy Category

Adverse reactions

Composition

Strengths and forms

Official product information

At a glance