Levothyroxine 0.150mg (150mcg) 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
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Pharmacologic Class
Thyroid replacement hormone; Synthetic L-thyroxine
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Pregnancy Category
Category A
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FDA Approved
Aug 1955
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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 when your thyroid gland doesn't make enough of this hormone (a condition called hypothyroidism). Taking this medicine helps your body work properly, improving symptoms like tiredness, weight gain, and feeling cold.
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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 your medicine exactly as prescribed by your doctor, usually once a day in the morning.
  • Take it on an empty stomach, at least 30-60 minutes before breakfast or any other food, beverages (other than water), or medications.
  • Consistency is key: try to take it at the same time each day.
  • Do not take calcium, iron, antacids, or fiber supplements within 4 hours of taking levothyroxine, as they can interfere with absorption.
  • Inform your doctor about all other medications, supplements, and herbal products you are taking.
  • Do not stop taking this medication without consulting your doctor, even if you feel better, as it is usually a lifelong treatment.

Dosing & Administration

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Adult Dosing

Standard Dose: Highly individualized, typically 1.6 mcg/kg/day for full replacement in primary hypothyroidism. 150 mcg is a common maintenance dose.
Dose Range: 25 - 300 mg

Condition-Specific Dosing:

initialHypothyroidism: Start with 25-50 mcg/day, titrate every 4-6 weeks based on TSH.
cardiacDisease: Start with 12.5-25 mcg/day, titrate slowly.
subclinicalHypothyroidism: 25-75 mcg/day, individualized based on TSH and symptoms.
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Pediatric Dosing

Neonatal: 10-15 mcg/kg/day (0-3 months)
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 (12-18 years, or >1.6 mcg/kg/day if growth complete)
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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, but monitor thyroid function closely.
Moderate: No specific adjustment needed, but monitor thyroid function closely.
Severe: No specific adjustment needed, but monitor thyroid function closely.

Pharmacology

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Mechanism of Action

Levothyroxine (T4) is a synthetic form of the natural thyroid hormone, L-thyroxine. It is converted to its active metabolite, L-triiodothyronine (T3), in peripheral tissues. T3 then enters the cell nucleus and binds to thyroid hormone receptors, which regulate gene expression, affecting protein synthesis and metabolism across various organ systems. This action restores normal metabolic rate, growth, and development in hypothyroid states.
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Pharmacokinetics

Absorption:

Bioavailability: 40-80% (variable, influenced by food and other medications)
Tmax: 2-4 hours
FoodEffect: Decreased absorption when taken with food, certain medications (e.g., calcium, iron, antacids, soy formula). Should be taken on an empty stomach.

Distribution:

Vd: 10-13 L
ProteinBinding: >99% (primarily to thyroxine-binding globulin [TBG], also to transthyretin and albumin)
CnssPenetration: Limited

Elimination:

HalfLife: 6-7 days (euthyroid); 9-10 days (hypothyroid); 3-4 days (hyperthyroid)
Clearance: Approximately 0.05 L/hr/kg
ExcretionRoute: Primarily renal (metabolites); approximately 20% excreted in feces (unchanged and metabolites)
Unchanged: Approximately 20% (fecal)
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Pharmacodynamics

OnsetOfAction: Gradual, clinical effects typically seen within 3-5 days, full therapeutic effect may take 4-6 weeks.
PeakEffect: Thyroid hormone levels stabilize after 4-6 weeks of consistent dosing.
DurationOfAction: Long, due to long half-life; effects persist for several days after discontinuation.

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

Serious Side Effects: Seek Medical Attention Immediately

Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical help right away:

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
Vomiting
Mood changes, such as:
+ Irritability
+ Nervousness
+ Excitability
+ 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
+ Limping
In infants:
+ Changes in the shape of the head and face

Other Possible Side Effects

Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience 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 within the first few months of treatment)

Reporting Side Effects

This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, consult 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, nervousness, tremors, excessive sweating, heat intolerance, unexplained weight loss, diarrhea, insomnia.
  • Symptoms of too little thyroid hormone (hypothyroidism) if dose is too low or missed: extreme fatigue, weight gain, constipation, dry skin, hair loss, feeling cold, depression.
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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 allergic reaction you experienced, including any symptoms.
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 with your doctor.

Additionally, provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter (OTC) medications you are taking
Any natural products or vitamins you are using
Your overall health status

It is vital to verify that it is safe to take this medication with all your other medications and health conditions. Never start, stop, or adjust the dosage of any medication without first consulting your doctor.
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Precautions & Cautions

Important Information for Patients Taking This Medication

It is essential to 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 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.

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

This medication may affect fertility, potentially making it difficult to become pregnant or father a child. If you plan to conceive, consult 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 and Breastfeeding

Inform your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. Your doctor will discuss the benefits and risks of this medication for you and your baby.

Special Considerations for Children

If your child is taking this medication and experiences a change in weight, consult your doctor, 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 teenagers. Regular growth checks may be necessary. Consult your doctor to discuss any concerns.
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Overdose Information

Overdose Symptoms:

  • Palpitations
  • Tachycardia (rapid heart rate)
  • Arrhythmias (irregular heartbeat)
  • Chest pain (angina)
  • Tremor
  • Nervousness
  • Insomnia
  • Diarrhea
  • Weight loss
  • Fever
  • Heat intolerance
  • Sweating

What to Do:

Seek immediate medical attention. Call 911 or your local emergency number. For poison control, call 1-800-222-1222.

Drug Interactions

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Contraindicated Interactions

  • Acute myocardial infarction
  • Uncorrected adrenal insufficiency
  • Untreated thyrotoxicosis
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Major Interactions

  • Amiodarone (can alter thyroid function)
  • Antacids (aluminum, magnesium, calcium) - decrease absorption
  • Bile acid sequestrants (cholestyramine, colestipol) - decrease absorption
  • Calcium carbonate/supplements - decrease absorption
  • Iron supplements - decrease absorption
  • Orlistat - decrease absorption
  • Proton pump inhibitors (e.g., omeprazole) - decrease absorption
  • Sucralfate - decrease absorption
  • Soy products/formula - decrease absorption
  • Warfarin (increased anticoagulant effect, monitor INR)
  • Insulin/oral hypoglycemics (increased requirements, monitor glucose)
  • Enzyme-inducing anticonvulsants (phenytoin, carbamazepine, phenobarbital) - increase levothyroxine metabolism
  • Rifampin - increases levothyroxine metabolism
  • Sertraline - may decrease levothyroxine efficacy
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Moderate Interactions

  • Beta-blockers (may decrease T4 to T3 conversion)
  • Estrogens (oral) - increase TBG, may increase levothyroxine requirement
  • Androgens - decrease TBG, may decrease levothyroxine requirement
  • Corticosteroids - may decrease T4 to T3 conversion
  • Digoxin (may decrease digoxin levels)
  • Theophylline (may decrease theophylline clearance)
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Minor Interactions

  • Not available

Monitoring

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Baseline Monitoring

Thyroid Stimulating Hormone (TSH)

Rationale: Primary diagnostic and monitoring tool for hypothyroidism.

Timing: Before initiating therapy.

Free Thyroxine (Free T4)

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

Timing: Before initiating therapy.

Clinical Symptoms of Hypothyroidism

Rationale: To establish baseline symptom severity and track improvement.

Timing: Before initiating therapy.

Cardiac Status (ECG, history)

Rationale: To assess for underlying cardiac disease, especially in elderly or those with known heart conditions, as thyroid hormone replacement can exacerbate cardiac symptoms.

Timing: Before initiating therapy, particularly in older adults or those with cardiac risk factors.

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Routine Monitoring

Thyroid Stimulating Hormone (TSH)

Frequency: Every 4-6 weeks until stable, then every 6-12 months once stable.

Target: 0.4-4.0 mIU/L (individualized based on age, comorbidities, and specific clinical situation).

Action Threshold: Adjust dose if TSH is outside target range; higher TSH indicates under-replacement, lower TSH indicates over-replacement.

Free Thyroxine (Free T4)

Frequency: May be monitored if TSH is suppressed (e.g., central hypothyroidism) or if there are concerns about TSH reliability. Less frequently than TSH.

Target: Reference range (e.g., 0.8-1.8 ng/dL), individualized.

Action Threshold: Adjust dose if Free T4 is outside target range, especially if TSH is not reliable.

Clinical Symptoms (e.g., fatigue, weight, mood, cold intolerance)

Frequency: At each visit.

Target: Resolution or improvement of hypothyroid symptoms.

Action Threshold: Persistent or worsening symptoms despite normal TSH may warrant further investigation or dose adjustment.

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Symptom Monitoring

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

Special Patient Groups

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Pregnancy

Levothyroxine is essential for normal fetal development and is safe to use during pregnancy. Thyroid hormone requirements often increase during pregnancy, requiring dose adjustments.

Trimester-Specific Risks:

First Trimester: Crucial for fetal neurological development. Untreated maternal hypothyroidism can lead to adverse outcomes (e.g., miscarriage, preterm birth, impaired neurocognitive development). Dose often needs to be increased.
Second Trimester: Continued need for adequate thyroid hormone. Monitor TSH regularly.
Third Trimester: Continued need for adequate thyroid hormone. Monitor TSH regularly.
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Lactation

Levothyroxine is considered safe during breastfeeding. Only small amounts are excreted into breast milk, and it does not adversely affect the infant.

Infant Risk: Low risk; compatible with breastfeeding.
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Pediatric Use

Essential for normal growth and development. Dosing is weight-based and generally higher per kilogram in younger children due to higher metabolic rates. Close monitoring of TSH and clinical status is crucial to ensure proper development.

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Geriatric Use

Lower starting doses are recommended due to increased sensitivity to thyroid hormones and a higher prevalence of underlying cardiac disease. Titrate dose slowly and monitor for cardiac symptoms. TSH target range may be slightly higher in very elderly patients.

Clinical Information

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Clinical Pearls

  • Take levothyroxine consistently at the same time each day, preferably 30-60 minutes before breakfast with water, to ensure optimal and consistent absorption.
  • Separate administration from calcium, iron, antacids, and other interacting medications by at least 4 hours.
  • Do not switch between different brands or generic formulations without consulting your doctor, as bioavailability can vary, potentially requiring dose adjustments.
  • Thyroid function tests (TSH, Free T4) should be monitored regularly, especially after dose changes, to ensure therapeutic levels.
  • Patients should be educated on symptoms of both under- and over-treatment to report to their healthcare provider.
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Alternative Therapies

  • Liothyronine (T3, synthetic)
  • Liotrix (T4/T3 combination, synthetic)
  • Desiccated Thyroid Extract (natural, animal-derived T4/T3 combination)
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Cost & Coverage

Average Cost: $10 - $50 per 30 tablets (generic)
Generic Available: Yes
Insurance Coverage: Tier 1 (Generic), 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 for more information. If you have any questions or concerns about this medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.