Levothyroxine 0.3mg (300mcg) Tab

Levothyroxine (T4) is a synthetic form of the naturally occurring thyroid hormone, L-thyroxine. It is converted to its active metabolite, L-triiodothyronine (T3), in peripheral tissues. T3 and T4 act by binding to thyroid hormone receptors in the cell nucleus, regulating gene expression and controlling numerous metabolic processes, including protein, carbohydrate, and lipid metabolism, and influencing growth and development.

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 irritability, nervousness, excitability, anxiety, or other emotional changes
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.

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.

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 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. You may need to adjust your diabetes medications. Monitor your blood sugar levels as directed by your doctor and undergo regular blood tests as advised.

When taking biotin or products containing biotin, stop using them 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 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 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 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.

• Amiodarone (can cause hypo- or hyperthyroidism)
• Antacids (aluminum, magnesium, calcium) - decrease absorption
• Bile acid sequestrants (cholestyramine, colestipol) - decrease absorption
• Calcium carbonate/supplements - decrease absorption
• Cation exchange resins (sodium polystyrene sulfonate) - decrease absorption
• Iron supplements - decrease absorption
• Orlistat - decrease absorption
• Proton pump inhibitors (PPIs) - may decrease absorption
• Sucralfate - decrease absorption
• Soy products/soy formula - decrease absorption
• Warfarin (increased anticoagulant effect)
• Antidiabetic agents (may increase blood glucose, requiring dose adjustment)
• Digoxin (decreased digoxin levels)
• SSRIs (sertraline) - may increase levothyroxine requirements
• Tyrosine kinase inhibitors (e.g., imatinib, sunitinib) - may increase levothyroxine requirements

• Beta-blockers (may decrease T4 to T3 conversion)
• Carbamazepine, Phenobarbital, Phenytoin, Rifampin (increase levothyroxine metabolism)
• Estrogens (increase TBG, increasing levothyroxine requirements)
• Androgens (decrease TBG, decreasing levothyroxine requirements)
• Glucocorticoids (may inhibit TSH secretion and T4 to T3 conversion)
• Iodine-containing products (e.g., contrast media) - can affect thyroid function
• Propylthiouracil (PTU) and Methimazole (inhibit thyroid hormone synthesis)
• Dietary fiber (decreased absorption)

• Coffee (may decrease absorption if taken concurrently)

• Fatigue
• Weight changes (gain or loss)
• Cold intolerance
• Constipation
• Dry skin
• Hair loss
• Bradycardia
• Depression
• Memory impairment
• Muscle aches/weakness
• Hoarseness
• Puffiness in face/eyes
• Nervousness
• Irritability
• Heat intolerance
• Palpitations
• Tremor
• Diarrhea
• Insomnia
• Weight loss (unexplained)
• Chest pain
• Shortness of breath

Levothyroxine is essential for maintaining euthyroid state during pregnancy. Thyroid hormone requirements often increase during pregnancy (by 25-50% or more), especially in the first trimester. Close monitoring of TSH (every 4-6 weeks) and dose adjustment are crucial to ensure adequate fetal neurological development. Category A: Studies in pregnant women have not shown an increased risk of fetal abnormalities.

Levothyroxine is compatible with breastfeeding. Only small amounts are excreted into breast milk, which are not clinically significant to the infant. It is considered safe for use during lactation (L1).

Dosing is weight-based and higher per kg in younger children due to higher metabolic rates. Close monitoring of TSH and FT4 is essential, especially in infants with congenital hypothyroidism, to ensure normal growth and neurodevelopment. Tablets can be crushed and suspended in a small amount of water or breast milk/formula and given by spoon or dropper; do not store suspension.

Lower starting doses are often recommended in elderly patients, especially those with underlying cardiovascular disease, due to increased sensitivity to thyroid hormones and risk of cardiac adverse events. Dose adjustments should be made in smaller increments and less frequently. Close monitoring for cardiac symptoms is important.

• Levothyroxine is a narrow therapeutic index drug; small changes in dose can have significant effects.
• Consistency is key: take at the same time each day, on an empty stomach, and avoid switching brands unless medically necessary and with close monitoring.
• Many medications and foods can interfere with levothyroxine absorption; counsel patients on separation times.
• TSH is the primary lab test for monitoring, but clinical symptoms are also important.
• Patients may not feel the full effect of a dose change for several weeks due to the long half-life.
• Over-replacement can lead to atrial fibrillation, osteoporosis, and other cardiac issues, especially in the elderly.
• Under-replacement can lead to persistent hypothyroid symptoms and long-term complications.

• Liothyronine (T3) - used in specific situations like myxedema coma or for short-term TSH suppression before radioactive iodine, but not typically for chronic replacement due to shorter half-life and greater fluctuations.

If your symptoms or health issues persist or worsen, it's 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 be sure 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 medical attention. When seeking help, be prepared to provide details about the overdose, including the medication taken, the amount, and the time it occurred.