Levothyroxine 500mcg Inj, 1 Vial

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 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.

Urgent Side Effects: Seek Medical Help Right Away

While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention immediately:

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, or anxious
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 experience no side effects or only 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)
Other side effects not listed here

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

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 to do so. This will help prevent potential interactions and ensure the safe use of this medication with your other treatments and health conditions.

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 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 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 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 getting pregnant or fathering a child. If you plan to become pregnant or father a child, 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 you and your baby.

Pediatric Patients

If you are giving this medication to a child and their 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.

• Amiodarone (may alter thyroid function and metabolism of levothyroxine)
• Anticoagulants (e.g., Warfarin - increased anticoagulant effect)
• Beta-blockers (may reduce conversion of T4 to T3)
• Cardiac glycosides (e.g., Digoxin - reduced therapeutic effect of digoxin)
• Insulin/Oral Hypoglycemics (increased insulin/hypoglycemic requirements)
• Sympathomimetics (increased risk of cardiac adverse effects)

• Antacids (e.g., aluminum hydroxide, calcium carbonate - reduced absorption if given orally, but less relevant for IV)
• Iron supplements (reduced absorption if given orally, but less relevant for IV)
• Sucralfate (reduced absorption if given orally, but less relevant for IV)
• Cholestyramine/Colestipol (reduced absorption if given orally, but less relevant for IV)
• Certain anticonvulsants (e.g., Phenytoin, Carbamazepine - increased metabolism of thyroid hormones)
• Estrogens/Oral Contraceptives (increased TBG, potentially increasing levothyroxine requirements)
• Androgens/Anabolic Steroids (decreased TBG, potentially decreasing levothyroxine requirements)
• Glucocorticoids (may inhibit TSH secretion and T4 to T3 conversion)
• SSRIs (may affect thyroid function tests)

• Dietary fiber (reduced absorption if given orally, but less relevant for IV)

• Fatigue
• Weight changes (gain or loss)
• Cold intolerance
• Constipation
• Dry skin
• Hair loss
• Bradycardia
• Depression
• Memory impairment
• Muscle aches
• Heat intolerance
• Palpitations
• Nervousness
• Tremor
• Diarrhea
• Insomnia
• Weight loss
• Tachycardia

Levothyroxine requirements often increase during pregnancy. It is crucial to maintain euthyroidism to support fetal development. Category A: Studies in pregnant women have not shown an increased risk of fetal abnormalities.

Levothyroxine is excreted in breast milk in minimal amounts and is considered compatible with breastfeeding. It does not appear to have adverse effects on the nursing infant.

Dosing is highly individualized based on age, weight, and severity of hypothyroidism. IV formulation is generally reserved for severe cases (e.g., myxedema coma) or when oral administration is not possible. Close monitoring of thyroid function tests and growth/development is essential.

Elderly patients may require lower doses of levothyroxine due to decreased metabolic clearance and increased sensitivity to thyroid hormones. Start with lower doses and titrate slowly. Increased risk of cardiac adverse effects, especially in those with underlying cardiovascular disease.

• IV levothyroxine is typically 50-75% of the patient's usual oral dose due to 100% bioavailability.
• For myxedema coma, a large IV loading dose is often given, followed by daily maintenance doses.
• Always check for co-existing adrenal insufficiency in myxedema coma and treat with glucocorticoids before or concurrently with levothyroxine to avoid precipitating an adrenal crisis.
• Administer IV levothyroxine slowly, usually over 1-3 minutes.
• Monitor cardiac status closely, especially in elderly patients or those with pre-existing heart disease, as rapid thyroid hormone replacement can precipitate angina or arrhythmias.
• Thyroid function tests (TSH, Free T4) should be monitored regularly to guide dose adjustments, but clinical response is also crucial.

• Liothyronine (T3) - sometimes used in combination with levothyroxine or alone in specific situations (e.g., myxedema coma, although levothyroxine is preferred due to longer half-life and more stable levels).
• Desiccated Thyroid Extract (e.g., Armour Thyroid) - contains both T4 and T3, derived from animal thyroid glands. Not available in IV form.

If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe use, never share your medication with others or take someone else's medication. Store all medications in a secure location, out of reach of children and pets, to prevent accidental ingestion. Dispose of unused or expired medications properly; do not flush them down the toilet or pour them down the drain unless instructed to do so by a healthcare professional or pharmacist. If you are unsure about the proper disposal method, consult your pharmacist, as they can provide guidance on disposal procedures and potential drug take-back programs in your area. Additionally, some medications may have a separate patient information leaflet; check with your pharmacist for more information. If you have any questions or concerns about this medication, discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately contact your local poison control center or seek medical attention. Be prepared to provide information about the medication taken, the amount, and the time it occurred to ensure prompt and effective treatment.