Thyro-Tabs Side Effects Center

Last updated on RxList: 4/25/2022
Thyro-Tabs Side Effects Center

What Is Thyro-Tabs?

Thyro-Tabs (levothyroxine sodium) tablets are L-thyroxine (T4) indicated as replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) con genital or acquired hypothyroidism; and as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.

What Are Side Effects of Thyro-Tabs?

Common side effects of Thyro-Tabs are primarily those of hyperthyroidism due to therapeutic overdosage including:

Dosage for Thyro-Tabs

Administer a dose of Thyro-Tabs once daily, preferably on an empty stomach, one-half to one hour before breakfast. The starting dose of Thyro-Tabs depends on a variety of factors, including age, body weight, cardiovascular status, and concomitant medications. Peak therapeutic effect may not be attained for 4-6 weeks.

What Drugs, Substances, or Supplements Interact with Thyro-Tabs?

Thyro-Tabs may interact with calcium carbonate, ferrous sulfate, orlistat, 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, anabolic steroids, glucocorticoids, slow-release nicotinic acid, salicylates, carbamazepine, furosemide, heparin, hydantoins, nonsteroidal anti-inflammatory drugs (NSAIDs), phenobarbital, rifampin, beta-adrenergic antagonists, glucocorticoids, and amiodarone. Tell your doctor all medications and supplements you use.

Thyro-Tabs During Pregnancy or Breastfeeding

Tell your doctor if you are pregnant or plan to become pregnant before using Thyro-Tabs. There are risks to the mother and fetus associated with untreated hypothyroidism in pregnancy. Since TSH levels may increase during pregnancy, TSH should be monitored and Thyro-Tabs dosage adjusted during pregnancy. Thyro-Tabs pass into breast milk but its effects on nursing infants are unknown. Consult your doctor before breastfeeding.

Additional Information

Our Thyro-Tabs (levothyroxine sodium) Tablets 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.

QUESTION

Where is the thyroid gland located? See Answer
Thyro-Tabs Consumer Information

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.

SLIDESHOW

Hyperthyroidism Symptoms and Treatment See Slideshow
Thyro-Tabs Professional Information

SIDE EFFECTS

Adverse reactions associated with Levothyroxine Sodium Tablets therapy are primarily those of hyperthyroidism due to therapeutic overdosage [see WARNINGS AND PRECAUTIONS and 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, muscle weakness, muscle spasm
  • Cardiovascular: palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest
  • Respiratory: dyspnea
  • Gastrointestinal: diarrhea, vomiting, abdominal cramps, 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 the institution of levothyroxine therapy.

Adverse Reactions In Children

Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in children receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants and premature closure of the epiphyses in children 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 and metabolism (e.g., absorption, synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to Levothyroxine Sodium Tablets (see Tables 2-5 below).

Table 2. Drugs That May Decrease T4 Absorption (Hypothyroidism)

Potential impact: Concurrent use may reduce the efficacy of Levothyroxine Sodium Tablets by binding and delaying or preventing absorption, potentially resulting in hypothyroidism.
Drug or Drug Class Effect
Calcium Carbonate
Ferrous Sulfate
Calcium carbonate may form an insoluble chelate with levothyroxine, and ferrous sulfate likely forms a ferric-thyroxine complex. Administer Levothyroxine Sodium Tablets at least 4 hours apart from these agents.
Orlistat Monitor patients treated concomitantly with orlistat and Levothyroxine Sodium Tablets for changes in thyroid

Bile Acid Sequestrants

  • Colesevela
  • Cholestyramine
  • Colestipol

Ion Exchange Resins

  • Kayexalate
  • Sevelamer
Bile acid sequestrants and ion exchange resins are known to decrease levothyroxine absorption. Administer Levothyroxine Sodium Tablets at least 4 hours prior to these drugs or monitor TSH levels.
Other drugs:
Proton Pump Inhibitors
Sucralfate
Antacids
  • Aluminum & MagnesiumHydroxides
  • 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 Levothyroxine Sodium Tablets results in an initial transient increase in FT4. Continued administration results in a decrease in serum T4 and normal FT4 and TSH concentrations.
Salicylates (greater than 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 (greater than 80 mg IV)
Heparin
Hydantoins
Non-Steroidal Anti-inflammatory Drugs
-Fenamates
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 increase 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 Levothyroxine Sodium Tablets 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’-diphospho-glucuronosyltransferase (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 greater than 160 mg/day)
In patients treated with large doses of propranolol (greater than 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 a hypothyroid patient is converted to the
Glucocorticoids
(e.g., Dexamethasone greater than or equal to 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 (See above).
Other drugs:
Amiodarone
Amiodarone inhibits peripheral conversion of levothyroxine (T4) to triiodothyronine (T3) and may cause isolated biochemical changes (increase in serum free-T4, and decreased or normal free-T3) in clinically euthyroid patients.

Antidiabetic Therapy

Addition of Levothyroxine Sodium Tablets 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 thyroid therapy is started, changed, or discontinued [see WARNINGS AND PRECAUTIONS].

Oral Anticoagulants

Levothyroxine Sodium Tablets increase 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 Tablets dose is increased. Closely monitor coagulation tests to permit appropriate and timely dosage adjustments.

Digitalis Glycosides

Levothyroxine Sodium Tablets 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 Levothyroxine Sodium Tablets 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. Levothyroxine Sodium Tablets may accelerate the onset of action of tricyclics. Administration of sertraline in patients stabilized on Levothyroxine Sodium Tablets may result in increased Levothyroxine Sodium Tablets requirements.

Ketamine

Concurrent use of ketamine and Levothyroxine Sodium Tablets may produce marked hypertension and tachycardia. Closely monitor blood pressure and heart rate in these patients.

Sympathomimetics

Concurrent use of sympathomimetics and Levothyroxine Sodium Tablets 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 Levothyroxine Sodium Tablets absorption thereby necessitating adjustments in dosing [see DOSAGE AND ADMINISTRATION]. Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of Levothyroxine Sodium Tablets 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, estrogen-containing oral contraceptives, and acute intermittent porphyria increase TBG concentration. 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 Thyro-Tabs (Levothyroxine Sodium)

© Thyro-Tabs Patient Information is supplied by Cerner Multum, Inc. and Thyro-Tabs Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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