Euthyrox 0.150mg (150mcg) Tab
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.
Drug Class
Thyroid hormone
Pharmacologic Class
Thyroid hormone replacement
Pregnancy Category
A
FDA Approved
Jan 1955
DEA Schedule
Not Controlled
Overview
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) and helps your body's metabolism work properly. It's important to take it exactly as prescribed to feel your best.
How to Use This Medicine
Taking Your Medication
To take this medication correctly, follow your doctor's instructions and read all the information provided. Take your dose on an empty stomach, at least 30 to 60 minutes before breakfast.
Important Administration Instructions
Some brands of this medication may cause choking, gagging, or trouble swallowing. If you have one of these products, take it with a full glass of water. Check with your pharmacist to see if this applies to your specific medication.
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 later use.
Interactions with Other Substances
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. Consult your doctor or pharmacist for guidance on 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. Additionally, if you regularly consume grapefruit juice or eat grapefruit, talk to your doctor about potential interactions.
Using the Correct Form of the Medication
There are different brands and forms of this medication. Do not switch between them without consulting the doctor who prescribed it.
Continuing Your Medication
Continue taking this 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, and do not store the removed medication for future use.
Missing a Dose
If you miss a dose, take it as soon as you remember. If it is close to the time for your next dose, skip the missed dose and resume your regular schedule. Do not take two doses at the same time or take extra doses.
To take this medication correctly, follow your doctor's instructions and read all the information provided. Take your dose on an empty stomach, at least 30 to 60 minutes before breakfast.
Important Administration Instructions
Some brands of this medication may cause choking, gagging, or trouble swallowing. If you have one of these products, take it with a full glass of water. Check with your pharmacist to see if this applies to your specific medication.
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 later use.
Interactions with Other Substances
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. Consult your doctor or pharmacist for guidance on 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. Additionally, if you regularly consume grapefruit juice or eat grapefruit, talk to your doctor about potential interactions.
Using the Correct Form of the Medication
There are different brands and forms of this medication. Do not switch between them without consulting the doctor who prescribed it.
Continuing Your Medication
Continue taking this 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, and do not store the removed medication for future use.
Missing a Dose
If you miss a dose, take it as soon as you remember. If it is close to the time for your next dose, skip the missed dose and resume your regular schedule. Do not take two doses at the same time or take extra doses.
Lifestyle & Tips
- Take on an empty stomach, typically 30-60 minutes before breakfast, with a full glass of water.
- Take at the same time each day for consistent absorption.
- Avoid taking with calcium, iron, antacids, or fiber supplements within 4 hours of your levothyroxine dose.
- Inform your doctor about all other medications, supplements, and herbal products you are taking, as many can interact with levothyroxine.
- Do not stop taking this medication without consulting your doctor, even if you feel better.
- Regular blood tests (TSH) are necessary to ensure you are on the correct dose.
Available Forms & Alternatives
Available Strengths:
- Euthyrox 100mcg Tablets
- Euthyrox 0.125mg (125mcg) Tablets
- Euthyrox 88mcg Tablets
- Euthyrox 0.05mg (50mcg) Tablets
- Euthyrox 0.075mg (75mcg) Tablets
- Euthyrox 0.137mg (137mcg) Tab
- Euthyrox 0.175mg (175mcg) Tabs
- Euthyrox 0.150mg (150mcg) Tab
- Euthyrox 0.025mg (25mcg) Tab
- Euthyrox 0.112mg (112mcg) Tablets
- Euthyrox 0.2mg (200mcg) Tab
- Euthyrox 0.075mg (75mcg) Tablets
- Euthyrox 0.088mg (88mcg) Tablets
- Euthyrox 0.100mg (100mcg) Tablets
Dosing & Administration
Adult Dosing
Standard Dose:
Initial dose typically 25-50 mcg orally once daily, adjusted by 12.5-25 mcg increments every 4-6 weeks based on TSH levels. Maintenance dose is highly individualized.
Dose Range:
50 - 200 mg
Condition-Specific Dosing:
hypothyroidism:
Initial: 1.6 mcg/kg/day orally once daily. Adjust dose by 12.5-25 mcg increments every 4-6 weeks based on TSH levels. Average full replacement dose is approximately 125 mcg/day.
myxedemaComa:
Initial: 300-500 mcg IV bolus, followed by 50-100 mcg IV daily until patient can take oral therapy.
Pediatric Dosing
Neonatal:
0-3 months: 10-15 mcg/kg/day orally once daily. Adjust based on TSH and T4.
Infant:
3-6 months: 8-10 mcg/kg/day orally once daily. Adjust based on TSH and T4.
Child:
6-12 months: 6-8 mcg/kg/day; 1-5 years: 5-6 mcg/kg/day; 6-12 years: 4-5 mcg/kg/day. All orally once daily, adjusted based on TSH and T4.
Adolescent:
12-17 years: 2-3 mcg/kg/day orally once daily, or 1.6 mcg/kg/day (full adult replacement dose) if puberty is complete. Adjust based on TSH and T4.
Dose Adjustments
Renal Impairment:
Mild:
No specific dose adjustment generally required.
Moderate:
No specific dose adjustment generally required.
Severe:
No specific dose adjustment generally required.
Dialysis:
Levothyroxine is highly protein-bound and not significantly removed by dialysis. No dose adjustment needed.
Hepatic Impairment:
Mild:
No specific dose adjustment generally required.
Moderate:
No specific dose adjustment generally required.
Severe:
No specific dose adjustment generally required.
Pharmacology
Mechanism of Action
Levothyroxine (T4) is a synthetic form of the natural thyroid hormone, thyroxine. It is converted to its active metabolite, liothyronine (T3), in peripheral tissues. T3 then enters the cell nucleus and binds to thyroid hormone receptors, regulating gene expression and controlling numerous metabolic processes, including protein synthesis, carbohydrate metabolism, lipid metabolism, and vitamin metabolism. It is essential for normal growth, development, and metabolism.
Pharmacokinetics
Absorption:
Bioavailability:
48-80% (average 60-80%)
Tmax:
2-4 hours
FoodEffect:
Decreased absorption when taken with food, certain medications (e.g., calcium, iron, antacids, soy products, fiber). Should be taken on an empty stomach, at least 30-60 minutes before breakfast.
Distribution:
Vd:
Approximately 10-13 L
ProteinBinding:
>99% (primarily to thyroxine-binding globulin [TBG], transthyretin [TTR], and albumin)
CnssPenetration:
Limited
Elimination:
HalfLife:
Approximately 6-7 days (euthyroid individuals); 9-10 days (hypothyroid individuals); 3-4 days (hyperthyroid individuals)
Clearance:
Approximately 0.05 L/hour
ExcretionRoute:
Primarily renal (approximately 80% as metabolites), with some fecal excretion (approximately 20%)
Unchanged:
<1%
Pharmacodynamics
OnsetOfAction:
Gradual, typically 3-5 days for initial effects, full therapeutic effect may take 4-6 weeks due to long half-life and need for TSH stabilization.
PeakEffect:
4-6 weeks (based on TSH normalization)
DurationOfAction:
Long, due to long half-life (effects persist for several days after discontinuation).
Safety & Warnings
Side Effects
Serious Side Effects: Seek Medical Help Right Away
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 immediately or seek emergency medical attention:
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 feeling irritable, nervous, excitable, anxious, or restless
Shakiness
Trouble sleeping
Sensitivity to heat
Excessive sweating
Fever
Muscle cramps
Muscle weakness
Flushing
Bone pain
Changes in menstrual periods
Additional Side Effects in Children and Infants
Children: Hip or knee pain, or a limp
Infants: Changes in the shape of the head and face
Other Possible Side Effects
Not everyone will experience side effects, and many people may only have mild symptoms. However, 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 within the first few months of treatment)
Reporting Side Effects
If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
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 immediately or seek emergency medical attention:
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 feeling irritable, nervous, excitable, anxious, or restless
Shakiness
Trouble sleeping
Sensitivity to heat
Excessive sweating
Fever
Muscle cramps
Muscle weakness
Flushing
Bone pain
Changes in menstrual periods
Additional Side Effects in Children and Infants
Children: Hip or knee pain, or a limp
Infants: Changes in the shape of the head and face
Other Possible Side Effects
Not everyone will experience side effects, and many people may only have mild symptoms. However, 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 within the first few months of treatment)
Reporting Side Effects
If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Chest pain
- Palpitations or rapid heart rate
- Excessive sweating
- Nervousness or anxiety
- Tremor
- Unexplained weight loss
- Diarrhea
- Insomnia
- Heat intolerance
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 that occurred.
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 (OTC) medications you are taking
Any natural products or vitamins you are using
* Your health problems
Carefully review your medications and health conditions with your doctor to confirm that it is safe to take this medication. Never start, stop, or change the dose of any medication without first consulting 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 that occurred.
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 (OTC) medications you are taking
Any natural products or vitamins you are using
* Your health problems
Carefully review your medications and health conditions with your doctor to confirm that it is safe to take this medication. Never start, stop, or change the dose of any medication without first consulting your doctor.
Precautions & Cautions
Important Information for All 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. Please note that it may take several weeks to experience the full effects of this medication.
Special Considerations
If you have diabetes (high blood sugar), consult your doctor, as this medication may affect 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 osteoporosis (weak bones), particularly after menopause. Discuss your individual risk factors with your doctor, who can help you determine if you are at higher risk.
This medication may also affect fertility, potentially leading to difficulties in getting pregnant or fathering a child. If you plan to conceive, consult your doctor before starting treatment.
Age-Related Considerations
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 with you, considering both your health and the baby's well-being.
Pediatric Patients
If you are giving this medication to a child and their weight changes, consult your doctor, as the dosage may need to be adjusted. Never give your child more of this medication than prescribed, as this may 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, so be sure to discuss this with your doctor.
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. Please note that it may take several weeks to experience the full effects of this medication.
Special Considerations
If you have diabetes (high blood sugar), consult your doctor, as this medication may affect 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 osteoporosis (weak bones), particularly after menopause. Discuss your individual risk factors with your doctor, who can help you determine if you are at higher risk.
This medication may also affect fertility, potentially leading to difficulties in getting pregnant or fathering a child. If you plan to conceive, consult your doctor before starting treatment.
Age-Related Considerations
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 with you, considering both your health and the baby's well-being.
Pediatric Patients
If you are giving this medication to a child and their weight changes, consult your doctor, as the dosage may need to be adjusted. Never give your child more of this medication than prescribed, as this may 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, so be sure to discuss this with your doctor.
Overdose Information
Overdose Symptoms:
- Headache
- Irritability
- Nervousness
- Sweating
- Diarrhea
- Tachycardia
- Arrhythmias
- Chest pain
- Tremor
- Insomnia
- Fever
- Heat intolerance
- Weight loss
What to Do:
Seek immediate medical attention or call 1-800-222-1222 (Poison Control Center). Treatment is symptomatic and supportive, often involving beta-blockers for cardiac symptoms.
Drug Interactions
Major Interactions
- Amiodarone (can cause hypo- or hyperthyroidism, alter T4 to T3 conversion)
- Warfarin (levothyroxine can increase anticoagulant effect, requiring dose reduction of warfarin)
- Tyrosine kinase inhibitors (e.g., imatinib, sunitinib, sorafenib - can decrease levothyroxine absorption or increase metabolism)
- Orlistat (can decrease levothyroxine absorption)
Moderate Interactions
- Antacids (aluminum, magnesium, calcium carbonate - decrease absorption; separate by 4 hours)
- Iron supplements (decrease absorption; separate by 4 hours)
- Calcium supplements (decrease absorption; separate by 4 hours)
- Proton pump inhibitors (e.g., omeprazole - may increase gastric pH, reducing absorption; monitor TSH)
- Sucralfate (decreases absorption; separate by 4 hours)
- Cholestyramine, colestipol (bile acid sequestrants - decrease absorption; separate by 4-6 hours)
- Soy products (can decrease absorption; monitor TSH)
- Dietary fiber (can decrease absorption; monitor TSH)
- Estrogens (increase TBG, potentially increasing levothyroxine requirement)
- Androgens (decrease TBG, potentially decreasing levothyroxine requirement)
- Carbamazepine, phenytoin, rifampin (induce hepatic metabolism of levothyroxine, increasing requirement)
- Beta-blockers (may reduce peripheral conversion of T4 to T3)
- Digoxin (levothyroxine may decrease digoxin levels)
Minor Interactions
- Grapefruit juice (may slightly decrease absorption, but generally not clinically significant if consistent intake)
Monitoring
Baseline Monitoring
Thyroid Stimulating Hormone (TSH)
Rationale: Primary diagnostic marker for hypothyroidism and key parameter for dose titration.
Timing: Before initiating therapy.
Free Thyroxine (FT4)
Rationale: Assesses circulating active thyroid hormone levels, especially useful in central hypothyroidism or when TSH is unreliable.
Timing: Before initiating therapy.
Clinical symptoms of hypothyroidism
Rationale: To establish baseline and track improvement.
Timing: Before initiating therapy.
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 based on patient age, comorbidities, and specific clinical situation, e.g., post-thyroidectomy for cancer may target lower TSH).
Action Threshold: TSH outside target range indicates need for dose adjustment.
Free Thyroxine (FT4)
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: FT4 outside target range, especially if TSH is also abnormal, indicates need for dose adjustment.
Clinical symptoms (e.g., fatigue, weight changes, cold intolerance, mood, hair/skin changes)
Frequency: At each visit, especially during dose titration.
Target: Resolution or improvement of hypothyroid symptoms.
Action Threshold: Persistent or worsening symptoms despite normal TSH may indicate need for further evaluation or dose adjustment.
Bone mineral density (BMD)
Frequency: Periodically, especially in postmenopausal women or patients on suppressive therapy, due to risk of osteoporosis with overtreatment.
Target: Maintain normal BMD.
Action Threshold: Evidence of bone loss may necessitate TSH target re-evaluation.
Symptom Monitoring
- Fatigue
- Weight gain
- Cold intolerance
- Constipation
- Dry skin
- Hair loss
- Bradycardia
- Depression
- Muscle aches
- Memory impairment
- Nervousness
- Irritability
- Heat intolerance
- Palpitations
- Tremor
- Weight loss
- Diarrhea
- Insomnia
- Tachycardia
Special Patient Groups
Pregnancy
Levothyroxine is safe and essential during pregnancy. Thyroid hormone requirements often increase during pregnancy (by 25-50% or more) due to increased TBG levels and fetal demand. Dose adjustments are frequently needed to maintain euthyroid state. Inadequate treatment of maternal hypothyroidism can lead to adverse fetal outcomes (e.g., impaired neurocognitive development, preterm birth, low birth weight).
Trimester-Specific Risks:
First Trimester:
Crucial for fetal brain development. Untreated maternal hypothyroidism poses significant risk.
Second Trimester:
Continued monitoring and dose adjustment as needed.
Third Trimester:
Continued monitoring and dose adjustment as needed.
Lactation
Levothyroxine is considered safe during breastfeeding. Only small amounts are excreted into breast milk, and it does not adversely affect the nursing infant. Maternal thyroid hormone requirements typically return to pre-pregnancy levels postpartum, requiring dose adjustment.
Infant Risk:
Minimal to none (L1 - Safest)
Pediatric Use
Essential for normal growth and development, including brain maturation. Dosing is weight-based and requires careful monitoring of TSH and FT4 to ensure adequate replacement and prevent over- or under-treatment. Lifelong therapy is usually required for congenital hypothyroidism.
Geriatric Use
Older adults may require lower starting doses and smaller dose increments due to increased sensitivity to thyroid hormones and higher prevalence of underlying cardiovascular disease. Careful titration and monitoring are crucial to avoid cardiac adverse effects. TSH target ranges may be slightly higher in very elderly patients.
Clinical Information
Clinical Pearls
- Levothyroxine is a narrow therapeutic index drug; consistency in brand, timing, and administration (empty stomach) is crucial.
- Many medications and foods can interfere with absorption; advise patients to take levothyroxine at least 30-60 minutes before breakfast and at least 4 hours apart from interacting agents.
- TSH is the primary monitoring parameter for dose adjustment in primary hypothyroidism. Allow at least 4-6 weeks after a dose change before re-checking TSH.
- Patients with central (secondary/tertiary) hypothyroidism should be monitored with Free T4, as TSH may not be a reliable indicator.
- Symptoms of over- or under-treatment often precede changes in TSH levels; educate patients on these symptoms.
- Patients with pre-existing cardiovascular disease should start with lower doses and titrate slowly to avoid exacerbation of angina or arrhythmias.
Alternative Therapies
- None (Levothyroxine is replacement therapy for a deficient hormone; there are no true 'alternatives' for treating hypothyroidism other than other forms of thyroid hormone replacement).
Cost & Coverage
Average Cost:
$10 - $50 per 30 tablets
Generic Available:
Yes
Insurance Coverage:
Tier 1 (preferred generic) or Tier 2 (preferred brand)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, 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 your 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.