Levothyroxine 0.112mg (112mcg) Tabs
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 replacement
Pharmacologic Class
Thyroid hormones
Pregnancy Category
Category A
FDA Approved
Jan 1949
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 when your thyroid gland doesn't make enough of this hormone, a condition called hypothyroidism. Taking this medicine helps your body work properly, regulating your energy, metabolism, and other important functions.
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 cause choking, gagging, or trouble swallowing. If you're taking one of these brands, be sure to take it with a full glass of water. Check with your pharmacist to see if this applies to your medication.
If you need to, you can crush your 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 your medication.
If you're taking other medications, they may need to be taken at a different time than your current 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 your 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 of Your 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're feeling well.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, away from the bathroom.
Protect your medication from heat and light.
If your medication comes in a blister pack, do not remove it until you're 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's 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.
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 cause choking, gagging, or trouble swallowing. If you're taking one of these brands, be sure to take it with a full glass of water. Check with your pharmacist to see if this applies to your medication.
If you need to, you can crush your 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 your medication.
If you're taking other medications, they may need to be taken at a different time than your current 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 your 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 of Your 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're feeling well.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, away from the bathroom.
Protect your medication from heat and light.
If your medication comes in a blister pack, do not remove it until you're 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's 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.
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 supplements, iron supplements, antacids, or other medications that can interfere with absorption. Separate by at least 4 hours.
- Do not switch between different brands or generic versions without consulting your doctor, as formulations can vary slightly and affect absorption.
- Inform your doctor about all other medications, supplements, and herbal products you are taking.
- Do not use for weight loss in individuals with normal thyroid function, as it can cause serious side effects.
Available Forms & Alternatives
Available Strengths:
- Levothyroxine 0.100mg(100mcg) Tab
- Levothyroxine 0.075mg (75mcg) Tabs
- Levothyroxine 0.125mg (125mcg) Tab
- Levothyroxine 0.05mg (50mcg) Tab
- Levothyroxine 0.025mg (25mcg) Tab
- Levothyroxine 0.112mg (112mcg) Tabs
- Levothyroxine 0.137mg (137mcg) Tab
- Levothyroxine 0.175mg (175mcg) Tabs
- Levothyroxine 500mcg Inj, 1 Vial
- Levothyroxine Sod 100mcg Inj, 1vial
- Levothyroxine 200mcg Inj, 1 Vial
- Levothyroxine 0.088mg (88mcg) Tab
- Levothyroxine 0.100mg (100mcg) Tab
- Levothyroxine 0.150mg (150mcg) Tab
- Levothyroxine 0.2mg (200mcg) Tab
- Levothyroxine 0.3mg (300mcg) Tab
- Levothyroxine 0.013mg (13mcg) Caps
- Levothyroxine 0.025mg (25mcg) Caps
- Levothyroxine 0.05mg (50mcg) Caps
- Levothyroxine 0.075mg (75mcg) Caps
- Levothyroxine 0.088mg (88mcg) Caps
- Levothyroxine 0.100mg (100mcg) Caps
- Levothyroxine 0.112mg (112mcg) Caps
- Levothyroxine 0.125mg (125mcg) Caps
- Levothyroxine 0.137mg (137mcg) Caps
- Levothyroxine 0.150mg (150mcg) Caps
- Levothyroxine 0.175mg (175mcg) Caps
- Levothyroxine 0.2mg (200mcg) Caps
- Levothyroxine 0.125mg (125mcg) Tabs
- Levothyroxine 100mcg/5ml Inj, 5ml
- Levothyroxine 100mcg/ml Inj, 1ml
- Levothyroxine 500mg/5ml Inj, 5ml
- Levothyroxine 200mcg/5ml Inj, 5ml
Dosing & Administration
Adult Dosing
Standard Dose:
Highly individualized, typically 1.6 mcg/kg/day for primary hypothyroidism. Initial doses often lower (e.g., 25-50 mcg/day) and titrated.
Dose Range:
25 - 300 mg
Condition-Specific Dosing:
primaryHypothyroidism:
1.6 mcg/kg/day (based on ideal body weight). Initial dose may be 50-100 mcg/day, adjusted by 12.5-25 mcg increments every 4-6 weeks.
subclinicalHypothyroidism:
25-75 mcg/day, titrated to normalize TSH.
myxedemaComa:
300-500 mcg IV loading dose, then 50-100 mcg IV daily.
cardiacDisease:
Initial dose 12.5-25 mcg/day, titrated slowly with caution.
Pediatric Dosing
Neonatal:
10-15 mcg/kg/day (0-3 months), adjusted based on TSH and T4.
Infant:
6-8 mcg/kg/day (3-6 months), 5-6 mcg/kg/day (6-12 months), adjusted based on TSH and T4.
Child:
4-5 mcg/kg/day (1-5 years), 3-4 mcg/kg/day (6-12 years), adjusted based on TSH and T4.
Adolescent:
2-3 mcg/kg/day (12-17 years), adjusted based on TSH and T4.
Dose Adjustments
Renal Impairment:
Mild:
No specific dose adjustment required.
Moderate:
No specific dose adjustment required.
Severe:
No specific dose adjustment required.
Dialysis:
No specific dose adjustment required; levothyroxine is highly protein-bound and not significantly removed by dialysis.
Hepatic Impairment:
Mild:
No specific dose adjustment required.
Moderate:
No specific dose adjustment required.
Severe:
No specific dose adjustment required; however, conversion of T4 to T3 may be impaired in severe liver disease, requiring careful monitoring.
Pharmacology
Mechanism of Action
Levothyroxine (L-thyroxine) is a synthetic form of thyroxine (T4), a naturally occurring thyroid hormone. It is converted to its active metabolite, liothyronine (T3), in peripheral tissues. T3 then enters the cell nucleus and binds to thyroid hormone receptors, which regulate gene expression and control various metabolic processes, including protein, carbohydrate, and lipid metabolism, and influence growth and development.
Pharmacokinetics
Absorption:
Bioavailability:
40-80% (highly variable, affected by food, gastric pH, and other medications)
Tmax:
2-4 hours
FoodEffect:
Decreased and delayed absorption when taken with food. Should be taken on an empty stomach, 30-60 minutes before breakfast.
Distribution:
Vd:
10-13 L
ProteinBinding:
>99% (primarily to thyroxine-binding globulin (TBG), transthyretin, and albumin)
CnssPenetration:
Limited (T3 crosses BBB more readily than T4)
Elimination:
HalfLife:
Approximately 7 days (range 6-10 days); shorter in hyperthyroidism, longer in hypothyroidism.
Clearance:
Approximately 0.05 L/hr/kg
ExcretionRoute:
Primarily renal (conjugated metabolites), some fecal (unabsorbed drug and biliary excretion of conjugated metabolites).
Unchanged:
<1% (renal)
Pharmacodynamics
OnsetOfAction:
Gradual, clinical effects typically seen within 3-5 days, but full therapeutic effect may take 4-6 weeks due to long half-life and need for TSH suppression.
PeakEffect:
Peak TSH suppression typically occurs after 4-6 weeks of consistent dosing.
DurationOfAction:
Long, due to long half-life; effects persist for several weeks after discontinuation.
Safety & Warnings
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.
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 or seek immediate 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 (in women)
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. 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 symptoms that bother you or do not go away, contact your doctor:
* Hair loss (usually temporary and resolves on its own within the first few months of treatment)
Reporting Side Effects
This is not an exhaustive list of possible side effects. 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.
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 immediate 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 (in women)
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. 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 symptoms that bother you or do not go away, contact your doctor:
* Hair loss (usually temporary and resolves on its own within the first few months of treatment)
Reporting Side Effects
This is not an exhaustive list of possible side effects. 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.
Seek Immediate Medical Attention If You Experience:
- Symptoms of too much thyroid hormone (hyperthyroidism): rapid heart rate, palpitations, chest pain, nervousness, irritability, insomnia, tremor, excessive sweating, heat intolerance, unexplained weight loss, diarrhea.
- Symptoms of too little thyroid hormone (hypothyroidism) despite treatment: persistent fatigue, weight gain, cold intolerance, constipation, dry skin, hair loss, depression, memory problems.
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 with your doctor.
Additionally, provide your doctor and pharmacist with a comprehensive list of all the medications you are taking, including:
Prescription medications
Over-the-counter (OTC) medications
Natural products
* Vitamins
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 change the dosage 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 with your doctor.
Additionally, provide your doctor and pharmacist with a comprehensive list of all the medications you are taking, including:
Prescription medications
Over-the-counter (OTC) medications
Natural products
* Vitamins
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 change the dosage of any medication without first consulting your doctor.
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. Please note that it may take several weeks to experience the full effects of this drug.
Special Considerations
If you have diabetes (high blood sugar), consult with 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 advised.
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 or answer any questions you may have.
This medication may also affect fertility, potentially leading to difficulties in getting pregnant or fathering a child. If you plan to conceive, consult with 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 for both you and your baby.
Pediatric Patients
If your child is taking this medication and experiences any weight changes, consult with 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, so be sure to discuss this with your doctor.
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. Please note that it may take several weeks to experience the full effects of this drug.
Special Considerations
If you have diabetes (high blood sugar), consult with 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 advised.
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 or answer any questions you may have.
This medication may also affect fertility, potentially leading to difficulties in getting pregnant or fathering a child. If you plan to conceive, consult with 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 for both you and your baby.
Pediatric Patients
If your child is taking this medication and experiences any weight changes, consult with 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, so be sure to discuss this with your doctor.
Overdose Information
Overdose Symptoms:
- Palpitations
- Tachycardia
- Arrhythmias (e.g., atrial fibrillation)
- Chest pain (angina)
- Tremor
- Nervousness
- Insomnia
- Diarrhea
- Weight loss
- Heat intolerance
- Fever
- Seizures (rare)
- Coma (rare)
What to Do:
Seek immediate medical attention. Call 911 or Poison Control at 1-800-222-1222. Management is supportive and symptomatic, often involving beta-blockers for cardiac symptoms and measures to reduce absorption if recent ingestion.
Drug Interactions
Major Interactions
- Amiodarone (can cause hypo- or hyperthyroidism, requires careful monitoring)
- Oral anticoagulants (e.g., warfarin - levothyroxine may increase anticoagulant effect, requiring dose reduction of anticoagulant)
- Sympathomimetics (e.g., pseudoephedrine, epinephrine - increased risk of cardiac adverse effects)
- Tyrosine kinase inhibitors (e.g., imatinib, sunitinib - may increase levothyroxine requirements)
- Ion exchange resins (e.g., cholestyramine, colestipol - significantly decrease levothyroxine absorption, separate by 4-6 hours)
- Sucralfate (decreases levothyroxine absorption, separate by 4-6 hours)
Moderate Interactions
- Antacids (aluminum, magnesium, calcium carbonate - decrease levothyroxine absorption, separate by 4 hours)
- Iron supplements (ferrous sulfate - decrease levothyroxine absorption, separate by 4 hours)
- Calcium supplements (calcium carbonate, calcium citrate - decrease levothyroxine absorption, separate by 4 hours)
- Proton pump inhibitors (e.g., omeprazole - may increase gastric pH, reducing levothyroxine absorption)
- H2 receptor blockers (e.g., ranitidine - may increase gastric pH, reducing levothyroxine absorption)
- Soy products (may decrease levothyroxine absorption)
- Dietary fiber (may decrease levothyroxine absorption)
- Phenytoin, Carbamazepine, Rifampin, Phenobarbital (induce hepatic metabolism of thyroid hormones, increasing levothyroxine requirements)
- Sertraline (may increase levothyroxine requirements)
- Estrogens (e.g., oral contraceptives, HRT - increase TBG, increasing levothyroxine requirements)
- Androgens (decrease TBG, decreasing levothyroxine requirements)
- Beta-blockers (may inhibit peripheral conversion of T4 to T3)
- Corticosteroids (may inhibit peripheral conversion of T4 to T3)
- Insulin/Oral Hypoglycemics (levothyroxine may increase blood glucose, requiring adjustment of antidiabetic agents)
Minor Interactions
- Grapefruit juice (minor effect on absorption, generally not clinically significant if consistent intake)
- Coffee (may impair absorption, separate by 30-60 minutes)
Monitoring
Baseline Monitoring
Thyroid Stimulating Hormone (TSH)
Rationale: Primary diagnostic test for hypothyroidism and key parameter for monitoring treatment efficacy.
Timing: Before initiating therapy.
Free Thyroxine (FT4)
Rationale: Assesses circulating unbound T4 levels, useful in certain conditions (e.g., central hypothyroidism, pregnancy, or when TSH is unreliable).
Timing: Before initiating therapy.
Clinical Symptoms of Hypothyroidism
Rationale: To establish baseline symptom severity 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 target may be lower for certain patients, e.g., post-thyroidectomy for cancer).
Action Threshold: TSH outside target range; adjust dose by 12.5-25 mcg/day.
Clinical Symptoms of Hypothyroidism/Hyperthyroidism
Frequency: At each visit.
Target: Resolution of hypothyroid symptoms without development of hyperthyroid symptoms.
Action Threshold: Persistent hypothyroid symptoms or emergence of hyperthyroid symptoms (e.g., palpitations, anxiety, weight loss, heat intolerance).
Free Thyroxine (FT4)
Frequency: Consider if TSH is suppressed or elevated despite dose adjustments, or in central hypothyroidism.
Target: 0.8-1.8 ng/dL (or laboratory reference range).
Action Threshold: FT4 outside target range, especially if TSH is also abnormal.
Symptom Monitoring
- Fatigue
- Weight gain
- Cold intolerance
- Constipation
- Dry skin
- Hair loss
- Bradycardia
- Depression
- Memory impairment
- Muscle aches
- Palpitations
- Anxiety
- Nervousness
- Irritability
- Weight loss (unexplained)
- Heat intolerance
- Diarrhea
- Tremor
- Tachycardia
- Insomnia
Special Patient Groups
Pregnancy
Levothyroxine is safe and essential during pregnancy. Thyroid hormone requirements typically increase during pregnancy (by 25-50% or more) due to increased TBG, placental deiodination, and fetal thyroid hormone needs. Dose adjustments are often necessary to maintain TSH within the trimester-specific target range (e.g., 0.1-2.5 mIU/L in 1st trimester).
Trimester-Specific Risks:
First Trimester:
Untreated maternal hypothyroidism in the first trimester is associated with increased risk of miscarriage, preterm birth, preeclampsia, and impaired neurocognitive development in the offspring. Levothyroxine is Category A and crucial.
Second Trimester:
Continued need for dose adjustment to maintain euthyroidism. Fetal thyroid gland begins to function, but maternal thyroid hormone remains important.
Third Trimester:
Dose requirements typically peak. Adequate maternal thyroid hormone is vital for fetal brain development.
Lactation
Levothyroxine is considered safe during breastfeeding. It is a natural hormone and is excreted into breast milk in minimal amounts that are not clinically significant to the infant.
Infant Risk:
L1 (Safest) - No adverse effects expected in breastfed infants. May even be beneficial if the infant has congenital hypothyroidism.
Pediatric Use
Essential for normal growth and development, especially brain development in infants and young children. Dosing is weight-based and higher per kg than in adults. Close monitoring of TSH and FT4 is crucial to prevent developmental delays and growth impairment. Tablets can be crushed and mixed with a small amount of water or breast milk/formula and given by spoon or dropper; do not mix with soy formula.
Geriatric Use
Older adults may require lower starting doses (e.g., 12.5-25 mcg/day) and slower titration due to increased risk of cardiac adverse effects (e.g., atrial fibrillation, angina) and potential for underlying cardiovascular disease. TSH target range may be slightly higher (e.g., up to 7.0 mIU/L) in very elderly or frail patients without specific symptoms.
Clinical Information
Clinical Pearls
- Consistency is key: Take levothyroxine at the same time every day, preferably in the morning on an empty stomach, 30-60 minutes before food or other medications.
- Separate from interacting substances: Advise patients to separate levothyroxine from calcium, iron, antacids, and other interacting medications by at least 4 hours.
- TSH is the primary monitoring parameter: TSH levels are the most sensitive indicator of thyroid status and guide dose adjustments.
- Full effect takes time: Due to its long half-life, it takes 4-6 weeks for TSH levels to stabilize after a dose change.
- Do not switch brands without consultation: Different formulations (even generics) can have slight differences in bioavailability, potentially affecting TSH levels. If a switch is made, re-check TSH in 4-6 weeks.
- Educate on symptoms: Patients should be aware of both hypothyroid and hyperthyroid symptoms to report any changes.
Alternative Therapies
- Liothyronine (Cytomel, Triostat - synthetic T3, shorter half-life, more potent, used for rapid effect or in specific conditions)
- Desiccated Thyroid Extract (e.g., Armour Thyroid, Nature-Throid - natural product from porcine thyroid glands, contains T4 and T3, variable potency)
Cost & Coverage
Average Cost:
$10 - $50 per 30 tablets
Generic Available:
Yes
Insurance Coverage:
Tier 1 (Generic), Tier 2-3 (Brand)
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 seeking help, be prepared to provide detailed information about the overdose, including the medication taken, the amount, and the time it occurred.