Medical Editor: John P. Cunha, DO, FACOEP
What Is Euthyrox?
Euthyrox (levothyroxine sodium) is L-thyroxine (T 4) indicated in pediatric and adult patients as replacement in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism; and as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer. Euthyrox is available in generic form.
What Are Side Effects of Euthyrox?
Common side effects of Euthyrox are primarily those of hyperthyroidism due to therapeutic overdosage and include:
- hives,
- difficulty breathing,
- swelling of your face, lips, tongue, or throat,
- chest pain or pressure,
- little or no urination,
- difficulty swallowing,
- dilated neck veins,
- extreme fatigue,
- fainting,
- fast, slow, irregular, pounding, or racing heartbeat or pulse,
- fever,
- heat intolerance,
- irregular breathing,
- irritability,
- menstrual changes,
- nausea,
- pain or discomfort in the arms, jaw, back, or neck,
- sweating,
- tremors,
- blurred or double vision,
- dizziness,
- eye pain,
- slowed growth in children,
- limp,
- pain in the hip or knee,
- seizures,
- severe headache,
- change in consciousness,
- cold, clammy skin,
- confusion,
- disorientation,
- fast or weak pulse,
- lightheadedness,
- loss of consciousness,
- loss of coordination, and
- slurring of speech
Get medical help right away, if you have any of the symptoms listed above.
Common side effects of Euthyrox are primarily those of hyperthyroidism due to therapeutic overdosage and include:
- irregular heartbeats,
- heart attack,
- shortness of breath,
- muscle spasm,
- headache,
- nervousness,
- irritability,
- insomnia,
- tremors,
- muscle weakness,
- increased appetite,
- weight loss,
- diarrhea,
- heat intolerance,
- menstrual irregularities, and
- skin rash
Seek medical care or call 911 at once if you have the following serious side effects:
- Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
- Serious heart symptoms such as fast, irregular, or pounding heartbeats; fluttering in your chest; shortness of breath; and sudden dizziness, lightheadedness, or passing out;
- Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors.
This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.
Dosage for Euthyrox
Administer a dose of Euthyrox once daily, on an empty stomach, one-half to one hour before breakfast. Administer Euthyrox at least 4 hours before or after drugs that are known to interfere with absorption.
What Drugs, Substances, or Supplements Interact with Euthyrox?
Euthyrox may interact with calcium carbonate, ferrous sulfate, bile acid sequestrants, ion exchange resins, proton pump inhibitors (PPIs), sucralfate, antacids, clofibrate, estrogen-containing oral contraceptives, estrogens (oral), heroin/methadone, 5-fluorouracil, mitotane, tamoxifen, androgens, steroids, asparaginase, glucocorticoids, slow-release nicotinic acid, salicylates, carbamazepine, furosemide, heparin, hydantoins, nonsteroidal anti-inflammatory drugs (NSAIDs), phenobarbital, rifampin, beta blockers, amiodarone, antidiabetic drugs or insulin, anticoagulants, digitalis glycosides, antidepressants, ketamine, sympathomimetics, and tyrosine-kinase inhibitors. Tell your doctor all medications and supplements you use.
Euthyrox During Pregnancy and Breastfeeding
Tell your doctor if you are pregnant or plan to become pregnant before using Euthyrox; Euthyrox dose requirements may increase during pregnancy. Euthyrox passes into breast milk. Consult your doctor before breastfeeding.
Additional Information
Our Euthyrox (levothyroxine sodium) Tablets, for Oral Use Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
SLIDESHOW
Hyperthyroidism Symptoms and Treatment See Slideshow3 pharmacies near 23917 have coupons for euthyrox (Brand Names:Euthyrox for 137MCG)
Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
- fast or irregular heartbeats;
- chest pain, pain spreading to your jaw or shoulder;
- shortness of breath;
- fever, hot flashes, sweating;
- tremors, or if you feel unusually cold;
- weakness, tiredness, sleep problems (insomnia);
- memory problems, feeling depressed or irritable;
- headache, leg cramps, muscle aches;
- feeling nervous or irritable;
- dryness of your skin or hair, hair loss;
- irregular menstrual periods; or
- vomiting, diarrhea, appetite changes, weight changes.
Certain side effects may be more likely in older adults.
Common side effects may include:
- chest pain, irregular heartbeats;
- shortness of breath;
- headache, leg cramps, muscle pain or weakness;
- tremors, feeling nervous or irritable, trouble sleeping;
- increased appetite;
- feeling hot;
- weight loss;
- changes in your menstrual periods;
- diarrhea; or
- skin rash, partial hair loss.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
QUESTION
Where is the thyroid gland located? See AnswerSIDE EFFECTS
Adverse reactions associated with EUTHYROX therapy are primarily those of hyperthyroidism due to therapeutic overdosage [see WARNINGS AND PRECAUTIONS, OVERDOSE]. They include the following:
- General: fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating
- Central Nervous System: headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia
- Musculoskeletal: tremors, muscular weakness and cramps
- Cardiovascular: palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest
- Respiratory: dyspnea
- Gastrointestinal: diarrhea, vomiting, abdominal cramps and elevations in liver function tests
- Dermatologic: hair loss, flushing, rash
- Endocrine: decreased bone mineral density
- Reproductive: menstrual irregularities, impaired fertility
Seizures have been reported rarely with levothyroxine therapy. Adverse Reactions in Pediatric Patients
Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in pediatric patients receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants and premature closure of the epiphyses in pediatric patients with resultant compromised adult height.
Hypersensitivity Reactions
Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various gastrointestinal symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness and wheezing. Hypersensitivity to levothyroxine itself is not known to occur.
DRUG INTERACTIONS
Drugs Known To Affect Thyroid Hormone Pharmacokinetics
Many drugs can exert effects on thyroid hormone pharmacokinetics (e.g. absorption, synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to EUTHYROX (see Tables 2 – 5).
Table 2: Drugs That May Decrease T4 Absorption (Hypothyroidism)
| Potential impact: Concurrent use may reduce the efficacy of EUTHYROX by binding and delaying orpreventing absorption, potentially resulting in hypothyroidism | |
| Drug or Drug Class | Effect |
| Calcium Carbonate | Calcium carbonate may form an insoluble chelate with levothyroxine, and ferrous sulfate likely forms a ferric-thyroxine complex. Administer EUTHYROX at least 4 hours apart from these agents. |
| Ferrous Sulfate | |
| Orlistat | Monitor patients treated concomitantly with orlistat and EUTHYROX for changes in thyroid function. |
| Bile Acid Sequestrants Bile Acid Sequestrants
|
Bile acid sequestrants and ion exchange resins are known to decrease levothyroxine absorption. Administer EUTHYROX at least 4 hours prior to these drugs or monitor thyrotropin (TSH) levels. |
| Other drugs: Proton Pump Inhibitors Sucralfate Antacids Aluminum & Magnesium Hydroxides Simethicone |
Gastric acidity is an essential requirement for adequate absorption of levothyroxine. Sucralfate, antacids and proton pump inhibitors may cause hypochlorhydria, affect intragastric pH, and reduce levothyroxine absorption. Monitor patients appropriately. |
Table 3: Drugs That May Alter T4 and Triiodothyronine (T3) Serum Transport Without Affecting Free-Thyroxine (FT4) Concentration (Euthyroidism)
| Drug or Drug Class | Effect |
| Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin / Methadone 5-Fluorouracil Mitotane Tamoxifen |
These drugs may increase serum thyroxine-binding globulin (TBG) concentration. |
| Androgens / Anabolic Steroids Asparaginase Glucocorticoids Slow-Release Nicotinic Acid |
These drugs may decrease serum TBG concentration. |
| Potential impact (below): Administration of these agents with EUTHYROX results in an initial transient increase in FT4. Continued administration results in a decrease in serum T4 and normal FT4 and TSH concentrations. | |
| Salicylates (> 2 g/day) | Salicylates inhibit binding of T4 and T3 to TBG and transthyretin. An initial increase in serum FT4 is followed by return of FT4 to normal levels with sustained therapeutic serum salicylate concentrations, although total T4 levels may decrease by as much as 30%. |
| Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-inflammatory Drugs
|
These drugs may cause protein-binding site displacement. Furosemide has been shown to inhibit the protein binding of T4 to TBG and albumin, causing an increased free-T4 fraction in serum. Furosemide competes for T4-binding sites on TBG, prealbumin, and albumin, so that a single high dose can acutely lower the total T4 level. Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total and free-T4 may be reduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. Closely monitor thyroid hormone parameters. |
Table 4: Drugs That May Alter Hepatic Metabolism of T4 (Hypothyroidism)
| Potential impact: Stimulation of hepatic microsomal drug-metabolizing enzyme activity may cause increased hepatic degradation of levothyroxine, resulting in increased EUTHYROX requirements. | |
| Drug or Drug Class | Effect |
| Phenobarbital Rifampin | Phenobarbital has been shown to reduce the response to thyroxine. Phenobarbital increases L-thyroxine metabolism by inducing uridine 5’-diphosphoglucuronosyltransferase (UGT) and leads to a lower T4 serum levels. Changes in thyroid status may occur if barbiturates are added or withdrawn from patients being treated for hypothyroidism. Rifampin has been shown to accelerate the metabolism of levothyroxine. |
Table 5: Drugs That May Decrease Conversion of T4 to T3
| Potential impact: Administration of these enzyme inhibitors decreases the peripheral conversion of T4 to T3, leading to decreased T3 levels. However, serum T4 levels are usually normal but may occasionally be slightly increased. | |
| Drug or Drug Class | Effect |
| Beta-adrenergic antagonists (e.g., Propranolol > 160 mg/day) |
In patients treated with large doses of propranolol (>160 mg/day), T3 and T4 levels change, TSH levels remain normal, and patients are clinically euthyroid. Actions of particular beta-adrenergic antagonists may be impaired when the hypothyroid patient is converted to the euthyroid state. |
| Glucocorticoids (e.g., Dexamethasone ≥ 4 mg/day) |
Short-term administration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels. However, long-term glucocorticoid therapy may result in slightly decreased T3 and T4 levels due to decreased TBG production (ee Table 3 above). |
| Other: Amiodarone |
Amiodarone inhibits peripheral conversion of levothyroxine (T4) to triiodothyronine (T3) and may cause isolated biochemical changes (increase in serumfree-T4, and decrease or normal free-T3) in clinically euthyroid patients. |
Antidiabetic Therapy
Addition of EUTHYROX therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements. Carefully monitor glycemic control, especially when EUTHYROX is started, changed, or discontinued [see WARNINGS AND PRECAUTIONS].
Oral Anticoagulants
EUTHYROX 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 EUTHYROX dose is increased. Closely monitor coagulation tests to permit appropriate and timely dosage adjustments.
Digitalis Glycosides
EUTHYROX may reduce the therapeutic effects of digitalis glycosides. Serum digitalis glycoside levels may decrease when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides.
Antidepressant Therapy
Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and EUTHYROX 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 central nervous system stimulation. EUTHYROX may accelerate the onset of action of tricyclics. Administration of sertraline in patients stabilized on EUTHYROX may result in increased EUTHYROX requirements.
Ketamine
Concurrent use of ketamine and EUTHYROX may produce marked hypertension and tachycardia. Closely monitor blood pressure and heart rate in these patients.
Sympathomimetics
Concurrent use of sympathomimetics and EUTHYROX 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.
Tyrosine-Kinase Inhibitors
Concurrent use of tyrosine-kinase inhibitors such as imatinib may cause hypothyroidism. Closely monitor TSH levels in such patients.
Drug-Food Interactions
Consumption of certain foods may affect EUTHYROX absorption thereby necessitating adjustments in dosing [see DOSAGE AND ADMINISTRATION]. Soybean flour (infant formula), cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of EUTHYROX from the gastrointestinal tract. Grapefruit juice may delay the absorption of levothyroxine and reduce its bioavailability.
Drug–Laboratory Test Interactions
Consider changes in TBG concentration when interpreting T4 and T3 values. Measure and evaluate unbound (free) hormone and/or determine the free-T4 index (FT4I) in this circumstance. Pregnancy, infectious hepatitis, estrogens, estrogencontaining oral contraceptives, and acute intermittent porphyria increase TBG concentrations. Nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, androgens and corticosteroids decrease TBG concentration. Familial hyper- or hypo-thyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9000.
Read the entire FDA prescribing information for Euthyrox (Levothyroxine Sodium Tablets)
© Euthyrox Patient Information is supplied by Cerner Multum, Inc. and Euthyrox Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.
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