Levothyroxine 0.100mg (100mcg) Tab

Levothyroxine (L-thyroxine) is a synthetic form of tetraiodothyronine (T4), a naturally occurring thyroid hormone. It is converted to its active metabolite, triiodothyronine (T3), in peripheral tissues. T3 and T4 exert their metabolic effects by controlling DNA transcription and protein synthesis. They bind to thyroid hormone receptors in the cell nucleus, regulating gene expression and influencing the rate of metabolism, growth, and development of all body systems.

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 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 change
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 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 are bothered by any of the following side effects or if they do not go away, contact your doctor:

* Hair loss (usually temporary and resolves on its own within the first few months of treatment)

This is not a comprehensive list of all 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.

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.

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 run out of this medication, as it may take several weeks to experience its full effects.

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 take biotin or products 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 risk factors with your doctor, who can help determine if you are at higher risk.

This medication may also affect fertility, potentially leading to difficulty getting pregnant or fathering a child. If you plan to become pregnant or father a child, consult your doctor before taking this medication.

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 you and your baby.

Pediatric Patients

If your child is taking this medication and experiences 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 discuss this with your doctor.

• Warfarin (increased anticoagulant effect, monitor INR)
• Sympathomimetic agents (increased risk of cardiac toxicity, especially in euthyroid patients)
• Amiodarone (can cause hypo- or hyperthyroidism, monitor thyroid function)
• Tyrosine kinase inhibitors (e.g., imatinib, sunitinib, sorafenib, pazopanib - may increase levothyroxine requirements)
• Orlistat (may reduce levothyroxine absorption, separate dosing)

• Calcium carbonate/supplements (decreased levothyroxine absorption, separate by ≥4 hours)
• Iron supplements (decreased levothyroxine absorption, separate by ≥4 hours)
• Antacids (aluminum, magnesium, simethicone - decreased levothyroxine absorption, separate by ≥4 hours)
• Sucralfate (decreased levothyroxine absorption, separate by ≥4 hours)
• Cholestyramine, Colestipol (decreased levothyroxine absorption, separate by ≥4 hours)
• Proton pump inhibitors (e.g., omeprazole, lansoprazole - may decrease levothyroxine absorption due to increased gastric pH)
• H2-receptor blockers (e.g., ranitidine, cimetidine - may decrease levothyroxine absorption)
• Soy products/soy formula (decreased levothyroxine absorption, may require higher dose)
• Dietary fiber (decreased levothyroxine absorption)
• Coffee (decreased levothyroxine absorption, separate by ≥60 minutes)
• Grapefruit juice (may decrease levothyroxine absorption)
• Rifampin, Carbamazepine, Phenytoin, Phenobarbital (increased levothyroxine metabolism, may require higher dose)
• Sertraline (may increase levothyroxine requirements)
• Estrogens (oral) / Oral Contraceptives (increase TBG, may increase levothyroxine requirements)
• Androgens / Anabolic steroids (decrease TBG, may decrease levothyroxine requirements)
• Beta-blockers (may decrease conversion of T4 to T3)
• Digoxin (levothyroxine may decrease digoxin levels, monitor digoxin levels)
• Antidiabetic agents (levothyroxine may increase blood glucose, monitor glucose and adjust antidiabetic dose)

• Certain foods (e.g., walnuts, cottonseed meal - may impair absorption, take consistently)

• Symptoms of hypothyroidism (e.g., fatigue, weight gain, constipation, cold intolerance, dry skin, hair loss, depression, bradycardia)
• Symptoms of hyperthyroidism (e.g., palpitations, tachycardia, nervousness, irritability, weight loss, heat intolerance, tremor, diarrhea, insomnia)

Levothyroxine is the drug of choice for hypothyroidism during pregnancy. Thyroid hormone requirements typically increase during pregnancy (often by 25-50% or more) due to increased TBG, placental deiodination, and fetal thyroid hormone needs. Close monitoring of TSH (every 4-6 weeks) and dose adjustment are essential to ensure adequate thyroid hormone levels for both mother and fetal neurodevelopment.

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

Essential for normal growth and development, especially neurocognitive development in infants and young children. Dosing is weight-based and generally higher per kilogram than in adults. Regular monitoring of TSH and T4 is critical to ensure proper development and prevent intellectual disability.

Lower starting doses (12.5-25 mcg/day) and slower titration increments (every 6-8 weeks) are recommended due to increased risk of cardiac adverse effects (e.g., atrial fibrillation, angina) in older patients, especially those with underlying cardiovascular disease. Monitor for cardiac symptoms.

• 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.
• Avoid brand switching: Due to potential differences in bioavailability, it is generally recommended to stick to the same brand of levothyroxine once stable, unless directed by a physician.
• Separate from interacting agents: Advise patients to separate levothyroxine administration from calcium, iron, antacids, and other interacting medications by at least 4 hours.
• Full effect takes time: Patients should be counseled that it takes several weeks (typically 4-6 weeks) for TSH levels to stabilize and for them to feel the full therapeutic effect.
• Symptoms are important: While TSH is the primary monitoring tool, always assess patient symptoms of hypo- or hyperthyroidism, as these guide clinical management.

• Liothyronine (synthetic T3, used in specific cases like myxedema coma or for short-term TSH suppression)
• Desiccated thyroid extract (natural thyroid hormone from porcine glands, containing T4 and T3)

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.