Levothyroxine 0.125mg (125mcg) Tab

Manufacturer MYLAN Active Ingredient Levothyroxine Tablets(lee voe thye ROKS een) Pronunciation lee voe thye ROKS een
WARNING: Do not use this drug for weight loss. Severe and sometimes deadly side effects may happen with this drug if it is taken in large doses or with other drugs for weight loss. If you have questions, talk with the doctor. @ COMMON USES: It is used to add thyroid hormone to the body.It is used to manage thyroid cancer.It may be given to you for other reasons. Talk with the doctor.
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Drug Class
Thyroid hormone replacement
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Pharmacologic Class
Thyroid preparation; Synthetic L-thyroxine (T4)
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Pregnancy Category
Category A
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FDA Approved
Jan 1965
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DEA Schedule
Not Controlled

Overview

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What is this medicine?

Levothyroxine is a medicine that replaces a hormone normally made by your thyroid gland. It's used to treat an underactive thyroid (hypothyroidism). Taking this medicine helps your body work properly by regulating your metabolism, energy levels, and other body functions.
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How to Use This Medicine

Taking Your Medication Correctly

To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely.

Take your medication on an empty stomach, at least 30 to 60 minutes before breakfast.
Some brands of this medication may be more likely to cause choking, gagging, or trouble swallowing. If this is the case, you must take it with a full glass of water. Check with your pharmacist to see if this applies to your specific product.
If you need to, you can crush the tablet and mix it with 1 or 2 teaspoons (5 or 10 mL) of water. Take the dose immediately after mixing, and do not store it for future use.

Important Interactions to Consider

Do not take iron products, antacids containing aluminum or magnesium, or calcium carbonate within 4 hours before or 4 hours after taking this medication.
If you take other medications, they may need to be taken at a different time than this medication. Consult with your doctor or pharmacist to determine the best schedule.
Certain foods, such as soybean flour (found in infant formula), may affect how this medication works in your body. Discuss this with your doctor.
If you regularly drink grapefruit juice or eat grapefruit, talk to your doctor about potential interactions.

Using the Correct Form and Brand of Medication

There are different brands and forms of this medication. Do not switch between them without consulting your doctor.
Continue taking your medication as directed by your doctor or healthcare provider, even if you feel well.

Storing and Disposing of Your Medication

Store your medication at room temperature in a dry place, away from the bathroom.
Protect it from heat and light.
If your medication comes in a blister pack, do not remove it until you are ready to take it. Do not store the removed medication for future use.

What to Do If You Miss a Dose

Take a missed dose as soon as you remember.
If it is close to the time for your next dose, skip the missed dose and return to your regular schedule.
* Do not take two doses at the same time or take extra doses.
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Lifestyle & Tips

  • Take on an empty stomach, typically 30-60 minutes before breakfast, with a full glass of water. Do not take with food or other medications.
  • Wait at least 4 hours after taking levothyroxine before taking antacids, iron supplements, calcium supplements, or bile acid sequestrants.
  • Take consistently at the same time each day.
  • Do not stop taking this medication without consulting your doctor, even if you feel better.
  • Inform your doctor about all other medications, supplements, and herbal products you are taking.
  • Regular blood tests (TSH) are necessary to ensure the correct dose.

Dosing & Administration

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Adult Dosing

Standard Dose: Highly individualized, typically 1.6 mcg/kg/day orally once daily. 0.125mg (125mcg) is a common maintenance dose.
Dose Range: 25 - 300 mg

Condition-Specific Dosing:

hypothyroidism_initial: Initial dose typically 25-50 mcg/day, adjusted by 12.5-25 mcg increments every 4-6 weeks based on TSH levels.
cardiac_disease: Initial dose 12.5-25 mcg/day, adjusted slowly.
myxedema_coma: IV administration, typically 200-500 mcg loading dose, then 100-300 mcg daily.
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Pediatric Dosing

Neonatal: 10-15 mcg/kg/day (0-3 months) for congenital hypothyroidism.
Infant: 6-8 mcg/kg/day (3-6 months), 5-6 mcg/kg/day (6-12 months).
Child: 4-5 mcg/kg/day (1-5 years), 3-4 mcg/kg/day (6-12 years).
Adolescent: 2-3 mcg/kg/day (12-17 years), or 1.6 mcg/kg/day (full growth and puberty).
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Dose Adjustments

Renal Impairment:

Mild: No specific adjustment needed.
Moderate: No specific adjustment needed.
Severe: No specific adjustment needed.
Dialysis: No specific adjustment needed; not significantly dialyzable.

Hepatic Impairment:

Mild: No specific adjustment needed.
Moderate: No specific adjustment needed.
Severe: No specific adjustment needed, but monitor thyroid function closely.

Pharmacology

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Mechanism of Action

Levothyroxine sodium is a synthetic L-isomer of thyroxine (T4), which is converted to its active metabolite, L-triiodothyronine (T3), in peripheral tissues. T3 and T4 bind to thyroid hormone receptors in the cell nucleus, regulating gene expression and controlling numerous metabolic processes, including protein, fat, and carbohydrate metabolism, and influencing growth and development.
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Pharmacokinetics

Absorption:

Bioavailability: 48-79% (variable, influenced by food and other medications)
Tmax: 2-4 hours
FoodEffect: Decreased absorption when taken with food, especially fiber, calcium, iron, and soy products. Should be taken on an empty stomach.

Distribution:

Vd: 10-13 L
ProteinBinding: >99% (primarily to thyroxine-binding globulin (TBG), transthyretin, and albumin)
CnssPenetration: Limited (T4 crosses BBB, but T3 is more active in CNS)

Elimination:

HalfLife: 6-7 days (euthyroid), 9-10 days (hypothyroid), 3-4 days (hyperthyroid)
Clearance: Approximately 0.05 L/hour
ExcretionRoute: Primarily renal (approximately 80% as metabolites), some fecal excretion (approximately 20%)
Unchanged: <1% (renal)
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Pharmacodynamics

OnsetOfAction: Gradual, clinical effects may take several days to weeks.
PeakEffect: Peak therapeutic effect typically seen 3-5 weeks after initiation or dose change.
DurationOfAction: Effects persist for several days after discontinuation due to long half-life.

Safety & Warnings

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BLACK BOX WARNING

Thyroid hormones, including Levothyroxine, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects.
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Side Effects

Urgent Side Effects: Seek Medical Help Right Away

While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention immediately:

Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of high blood pressure, including:
+ Severe headache or dizziness
+ Passing out
+ Changes in eyesight
Chest pain or pressure
Fast or abnormal heartbeat
Shortness of breath
Sudden weight gain or swelling in the arms or legs
Headache
Feeling tired or weak
Changes in appetite
Unintentional weight changes
Diarrhea, stomach cramps, or vomiting
Mood changes, such as irritability, nervousness, excitability, or anxiety
Shakiness
Trouble sleeping
Sensitivity to heat
Excessive sweating
Fever
Muscle cramps
Muscle weakness
Flushing
Bone pain
Changes in menstrual periods
In children: hip or knee pain, or a limp
In infants: changes in the shape of the head and face

Other Possible Side Effects

Like all medications, this drug can cause side effects. Many people may not experience any side effects or may only have mild ones. If you notice any of the following side effects or any other unusual symptoms, contact your doctor for advice:

Hair loss (usually temporary and resolves on its own)
Other side effects not listed here

If you have questions or concerns about side effects, talk to your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
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Seek Immediate Medical Attention If You Experience:

  • Symptoms of too much thyroid hormone (hyperthyroidism): rapid heart rate, palpitations, chest pain, excessive sweating, heat intolerance, nervousness, tremor, insomnia, weight loss, diarrhea.
  • Symptoms of too little thyroid hormone (hypothyroidism): extreme fatigue, weight gain, cold intolerance, constipation, dry skin, hair loss, depression, slow heart rate.
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Before Using This Medicine

Before Taking This Medication: Important Information to Share with Your Doctor

It is essential to inform your doctor about the following:

Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
Certain health conditions, including:
+ An overactive thyroid gland
+ A weak adrenal gland
+ Difficulty swallowing

This list is not exhaustive, and it is crucial to discuss all your health problems and medications with your doctor.

To ensure your safety, provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter medications you are taking
Any natural products or vitamins you are using
* Your health problems

Before making any changes to your medication regimen, including starting, stopping, or adjusting the dose of any drug, consult with your doctor to confirm it is safe to do so.
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Precautions & Cautions

Important Information for All Patients Taking This Medication

It is crucial that you inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. To ensure uninterrupted treatment, do not allow your supply of this medication to run out. You may not experience the full effects of this medication for several weeks.

If you have diabetes (high blood sugar), consult with your doctor, as this medication may affect your blood sugar control. Your doctor may need to adjust your diabetes medications. Be sure to monitor your blood sugar levels as directed by your doctor and undergo regular blood tests as recommended.

If you are taking biotin or a product containing biotin, stop taking it at least 2 days before having your thyroid levels checked to ensure accurate test results.

Potential Risks and Side Effects

High doses of this medication may increase the risk of developing weak bones (osteoporosis), particularly after menopause. Discuss your risk factors with your doctor, who can help determine if you are at higher risk.

This medication may also affect fertility, potentially making it difficult to become pregnant or father a child. If you plan to conceive, consult with your doctor before starting treatment.

If you are 65 or older, use this medication with caution, as you may be more susceptible to side effects.

Pregnancy, Breastfeeding, and Pediatric Use

If you are pregnant, plan to become pregnant, or are breastfeeding, discuss the benefits and risks of this medication with your doctor to ensure the best possible outcome for you and your baby.

When giving this medication to a child, monitor their weight closely and consult with your doctor if it changes, as the dosage may need to be adjusted. Never give your child more of this medication than prescribed, as this can increase the risk of severe side effects. In some cases, this medication may affect growth in children and teens, so regular growth checks may be necessary. Consult with your doctor to discuss any concerns.
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Overdose Information

Overdose Symptoms:

  • Palpitations
  • Tachycardia (rapid heart rate)
  • Arrhythmias
  • Chest pain (angina)
  • Tremor
  • Nervousness
  • Insomnia
  • Diarrhea
  • Weight loss
  • Heat intolerance
  • Fever
  • Seizures (rare)
  • Heart failure (in susceptible patients)

What to Do:

Seek immediate medical attention or call a poison control center (1-800-222-1222). Treatment is symptomatic and supportive, including beta-blockers for cardiac effects and measures to reduce absorption if recent ingestion.

Drug Interactions

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Major Interactions

  • Amiodarone (can cause hypo- or hyperthyroidism, monitor thyroid function)
  • Antacids (aluminum, magnesium, calcium) - decrease absorption of levothyroxine
  • Bile acid sequestrants (cholestyramine, colestipol) - decrease absorption of levothyroxine
  • Calcium carbonate/supplements - decrease absorption of levothyroxine
  • Cation exchange resins (sodium polystyrene sulfonate) - decrease absorption of levothyroxine
  • Iron supplements - decrease absorption of levothyroxine
  • Orlistat - may decrease absorption of levothyroxine
  • Proton pump inhibitors (PPIs) - may decrease absorption of levothyroxine due to increased gastric pH
  • Sucralfate - decreases absorption of levothyroxine
  • Tyrosine kinase inhibitors (e.g., imatinib, sunitinib) - may alter thyroid function, requiring dose adjustment of levothyroxine
  • Warfarin - levothyroxine may increase anticoagulant effect (monitor INR)
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Moderate Interactions

  • Anticonvulsants (carbamazepine, phenytoin, phenobarbital) - increase levothyroxine metabolism
  • Antidepressants (tricyclics, SSRIs) - may increase cardiac effects of levothyroxine
  • Beta-blockers - may decrease conversion of T4 to T3
  • Corticosteroids - may decrease TSH secretion and T4 to T3 conversion
  • Estrogens (oral) - increase TBG, potentially increasing levothyroxine requirement
  • Furosemide (>80 mg IV) - may displace T4 from protein binding
  • Lovastatin - isolated reports of thyroid dysfunction
  • Propylthiouracil (PTU) / Methimazole - inhibit thyroid hormone synthesis and T4 to T3 conversion
  • Rifampin - increases levothyroxine metabolism
  • Soy products - may decrease absorption of levothyroxine
  • Theophylline - clearance may be altered by thyroid status
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Minor Interactions

  • Dietary fiber - may decrease absorption of levothyroxine

Monitoring

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Baseline Monitoring

Thyroid Stimulating Hormone (TSH)

Rationale: Primary indicator of thyroid function and adequacy of levothyroxine replacement.

Timing: Before initiating therapy.

Free Thyroxine (Free T4)

Rationale: Assesses circulating unbound T4 levels, useful in certain conditions (e.g., central hypothyroidism, pregnancy).

Timing: Before initiating therapy.

Clinical symptoms of hypothyroidism

Rationale: To establish baseline and track improvement.

Timing: Before initiating therapy.

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Routine Monitoring

Thyroid Stimulating Hormone (TSH)

Frequency: Every 4-6 weeks after initiation or dose change, then every 6-12 months once stable.

Target: 0.4-4.0 mIU/L (individualized for patient age, comorbidities, and specific conditions like pregnancy or thyroid cancer).

Action Threshold: TSH outside target range indicates need for dose adjustment.

Free Thyroxine (Free T4)

Frequency: May be checked with TSH, especially if TSH is suppressed or in central hypothyroidism.

Target: 0.8-1.8 ng/dL (or laboratory specific reference range).

Action Threshold: Abnormal levels may indicate over- or under-treatment.

Clinical symptoms (e.g., fatigue, weight, mood, heart rate)

Frequency: At each visit.

Target: Resolution of hypothyroid symptoms, absence of hyperthyroid symptoms.

Action Threshold: Persistent or new symptoms warrant further investigation and potential dose adjustment.

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Symptom Monitoring

  • Fatigue
  • Weight changes (gain or loss)
  • Cold intolerance
  • Constipation
  • Dry skin
  • Hair loss
  • Bradycardia (slow heart rate)
  • Depression
  • Memory impairment
  • Muscle aches
  • Nervousness
  • Palpitations
  • Heat intolerance
  • Diarrhea
  • Tremor
  • Insomnia

Special Patient Groups

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Pregnancy

Levothyroxine is essential for normal fetal development and is safe and often required during pregnancy. Thyroid hormone requirements typically increase during pregnancy.

Trimester-Specific Risks:

First Trimester: Untreated maternal hypothyroidism can lead to adverse fetal outcomes (e.g., impaired neurocognitive development, preterm birth, low birth weight). Dose often needs to be increased.
Second Trimester: Continued monitoring and dose adjustment are crucial to maintain euthyroid state.
Third Trimester: Dose may need further adjustment. Continue monitoring TSH every 4-6 weeks.
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Lactation

Levothyroxine is compatible with breastfeeding. Minimal amounts are excreted into breast milk and do not adversely affect the infant.

Infant Risk: L1 (Safest) - No known risk to the infant.
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Pediatric Use

Dosing is weight-based and higher per kg in younger children due to higher metabolic rates. Regular monitoring of TSH and Free T4 is crucial for proper growth and neurocognitive development. Lifelong treatment is usually required for congenital hypothyroidism.

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Geriatric Use

Lower initial doses are often recommended due to increased sensitivity to thyroid hormones and higher prevalence of underlying cardiac disease. Dose adjustments should be made slowly and cautiously, monitoring for cardiac symptoms.

Clinical Information

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Clinical Pearls

  • Levothyroxine is a narrow therapeutic index drug; small dose changes can have significant effects.
  • Consistency is key: advise patients to take it at the same time every day, preferably in the morning on an empty stomach.
  • Educate patients about potential interactions with food, supplements (calcium, iron), and other medications (antacids, PPIs). Separate administration by at least 4 hours.
  • TSH is the primary monitoring parameter; Free T4 may be used in specific cases (e.g., central hypothyroidism, pregnancy, TSH suppression).
  • Symptoms of over- or under-treatment can mimic other conditions; always consider thyroid status.
  • Patients with cardiac disease should start at lower doses and titrate slowly to avoid exacerbating cardiac symptoms.
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Alternative Therapies

  • No direct therapeutic alternatives for thyroid hormone replacement in hypothyroidism; it is a replacement therapy.
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Cost & Coverage

Average Cost: $10 - $50 per 30 tablets (for generic 125mcg)
Generic Available: Yes
Insurance Coverage: Tier 1 (Generic) or Tier 2/3 (Brand)
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General Drug Facts

If your symptoms or health issues persist or worsen, it is essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it's a good idea to check with your pharmacist. If you have any questions or concerns about this medication, don't hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When reporting the incident, be prepared to provide details about the medication taken, the amount, and the time it occurred.