Levothyroxine 0.100mg (100mcg) Caps

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, which regulate gene expression and control various metabolic processes, including protein synthesis, carbohydrate metabolism, lipid metabolism, and cellular respiration. It is essential for normal growth, development, and metabolism.

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. 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 within the first few months of treatment)

Reporting Side Effects

This is not a comprehensive list of all possible side effects. 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.

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, tell your doctor and pharmacist about:
All prescription and over-the-counter (OTC) medications you are taking
Any natural products or vitamins you are using
* All your health problems

Before starting, stopping, or changing the dose of any medication, including this one, consult with your doctor to confirm it is safe for you to do so.

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 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

If you are pregnant, plan to become pregnant, or are breastfeeding, inform your doctor, who will discuss the benefits and risks of this medication to you and your baby.

Pediatric Patients

If your child is taking this medication and experiences any changes in weight, 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.

• Amiodarone (alters thyroid hormone metabolism)
• Warfarin (may increase anticoagulant effect)
• Antacids (aluminum, magnesium, calcium), Iron, Sucralfate, Bile Acid Sequestrants (cholestyramine, colestipol), Sodium Polystyrene Sulfonate (decreased levothyroxine absorption)
• Proton Pump Inhibitors (may decrease levothyroxine absorption)
• Orlistat (may decrease levothyroxine absorption)
• Tyrosine Kinase Inhibitors (e.g., imatinib, sunitinib, sorafenib) (may increase levothyroxine requirements)
• Estrogens (oral) / Selective Estrogen Receptor Modulators (SERMs) (e.g., tamoxifen, raloxifene) (increase TBG, increasing levothyroxine requirements)
• Androgens / Anabolic Steroids (decrease TBG, decreasing levothyroxine requirements)
• Glucocorticoids (large doses) (inhibit TSH secretion, alter T4 to T3 conversion)
• Beta-blockers (e.g., propranolol) (may inhibit T4 to T3 conversion)
• Iodine-containing products (e.g., radiographic contrast agents, povidone-iodine) (may induce hypo- or hyperthyroidism)

• Antidiabetic agents (may increase blood glucose, requiring dose adjustment of antidiabetic agent)
• Digoxin (may decrease digoxin levels)
• Antidepressants (tricyclics, SSRIs) (may increase cardiac effects of both drugs)
• Ketamine (may cause hypertension and tachycardia)
• Sympathomimetics (increased risk of cardiac effects)
• Rifampin, Carbamazepine, Phenytoin, Phenobarbital (increase levothyroxine metabolism, increasing requirements)
• Soy products, dietary fiber (may decrease absorption)

• Caffeine (minimal effect on absorption)
• Grapefruit juice (minimal effect on absorption)

• Hypothyroidism: Fatigue, weight gain, constipation, cold intolerance, dry skin, hair loss, depression, bradycardia, muscle aches, menstrual irregularities.
• Hyperthyroidism (overdose/over-replacement): Palpitations, tachycardia, anxiety, insomnia, tremors, weight loss, heat intolerance, diarrhea, sweating, chest pain, shortness of breath.

Levothyroxine is Category A and is essential for fetal neurological development. Thyroid hormone requirements often increase during pregnancy (by 25-50% or more). Dose adjustments are typically needed to maintain TSH within the trimester-specific target range.

Levothyroxine is considered safe during breastfeeding. Only small amounts are excreted into breast milk, which are not expected to cause adverse effects in the infant. Maternal thyroid hormone levels should be monitored and maintained within the normal range.

Essential for normal growth and development, including brain maturation. Dosing is weight-based and higher per kg than in adults, especially in infants. Regular monitoring of TSH and FT4 is crucial to ensure adequate replacement and prevent developmental delays.

Lower starting doses (e.g., 12.5-25 mcg/day) are recommended, especially in patients with underlying cardiac disease, due to increased sensitivity to thyroid hormones and potential for exacerbating cardiac conditions. Dose titration should be gradual (6-8 week intervals).

• Always take levothyroxine on an empty stomach, 30-60 minutes before breakfast, with water, and separate from other medications and supplements by at least 4 hours.
• Consistency is key: take at the same time every day.
• Capsule formulation (Tirosint) may have more consistent absorption and be less affected by food or gastric pH compared to tablets, which can be beneficial for patients with absorption issues or on PPIs.
• TSH is the primary lab test for monitoring, but clinical symptoms are also vital. Treat the patient, not just the lab value.
• Patients may require higher doses during pregnancy, with certain medications (e.g., estrogens, enzyme inducers), or with malabsorption syndromes.
• Patients may require lower doses with aging, after starting androgens, or with resolution of malabsorption.
• Educate patients about symptoms of both under- and over-replacement.
• Never use for weight loss in euthyroid individuals due to serious cardiac risks.

• Liothyronine (T3, Cytomel): Synthetic T3, shorter half-life, more potent, used in specific cases (e.g., thyroid cancer withdrawal, myxedema coma).
• Desiccated Thyroid Extract (Armour Thyroid, Nature-Throid): Natural thyroid hormone from porcine thyroid glands, contains both T4 and T3. Dosing can be less precise due to variable T4/T3 ratios.
• Liotrix (Thyrolar): Synthetic combination of T4 and T3 in a fixed 4:1 ratio.

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 is a good idea to check with your pharmacist for more information. If you have any questions or concerns about your medication, do not 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 emergency medical attention. When seeking help, be prepared to provide details about the overdose, including the medication taken, the amount, and the time it occurred.