Levothyroxine Sod 100mcg Inj, 1vial

Levothyroxine sodium is a synthetic L-isomer of thyroxine (T4). T4 is converted to its active metabolite, L-triiodothyronine (T3), in peripheral tissues. T3 and T4 bind to thyroid receptor proteins in the cell nucleus and exert metabolic effects through gene transcription and protein synthesis, regulating metabolism, 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 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)

Reporting Side Effects

This is not a complete list of possible side effects. If you have questions or concerns about side effects, contact 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 and its symptoms.
Certain health conditions, including:
+ Overactive thyroid gland (hyperthyroidism)
+ Weak adrenal gland (adrenal insufficiency)

This list is not exhaustive, and it is crucial to discuss all your health problems and medications with your doctor.

To ensure safe treatment, provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter (OTC) medications you are taking
Natural products and vitamins you are using
* Any health problems you have

Do not start, stop, or change the dosage of any medication without first consulting your doctor to confirm it is safe to do so.

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 allow your supply of this medication to run out. You may not experience the full effects of this medication for several weeks.

If you have diabetes (high blood sugar), consult your doctor, as this medication may affect your blood sugar control. Your doctor may need to adjust your diabetes medications. 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.

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 of developing osteoporosis.

This medication may affect fertility, making it more difficult to become pregnant or father a child. If you plan to conceive, consult your doctor before starting treatment.

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 potential benefits and risks of this medication to you and your baby.

Special Considerations for Children

If your child is taking this medication and experiences a change in weight, consult 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. Consult your doctor to discuss any concerns.

• Amiodarone (can cause hypo- or hyperthyroidism, alters T4 to T3 conversion)
• Anticoagulants (e.g., Warfarin - may increase anticoagulant effect)
• Beta-blockers (e.g., Propranolol - may decrease T3 conversion)
• Cardiac glycosides (e.g., Digoxin - may decrease digoxin levels)
• Sympathomimetics (e.g., Epinephrine - increased risk of cardiac adverse effects)
• Tyrosine kinase inhibitors (e.g., Sunitinib, Imatinib - may increase levothyroxine requirements)

• Antacids (e.g., Aluminum hydroxide, Calcium carbonate - may impair absorption of oral levothyroxine, less relevant for IV but important if transitioning)
• Iron supplements (may impair absorption of oral levothyroxine, less relevant for IV)
• Sucralfate (may impair absorption of oral levothyroxine, less relevant for IV)
• Bile acid sequestrants (e.g., Cholestyramine, Colestipol - may impair absorption of oral levothyroxine, less relevant for IV)
• Proton pump inhibitors (e.g., Omeprazole - may impair absorption of oral levothyroxine, less relevant for IV)
• Estrogens (e.g., Oral contraceptives, HRT - increase TBG, increasing levothyroxine requirements)
• Androgens (decrease TBG, decreasing levothyroxine requirements)
• Glucocorticoids (e.g., Dexamethasone - may decrease TSH secretion, alter T4 to T3 conversion)
• Phenytoin, Carbamazepine, Rifampin (induce hepatic metabolism, increasing levothyroxine requirements)
• Sertraline (may increase levothyroxine requirements)
• Orlistat (may impair absorption of oral levothyroxine, less relevant for IV)

• Dietary fiber (may impair absorption of oral levothyroxine, less relevant for IV)

• Fatigue
• Weight changes (gain or difficulty losing)
• Cold intolerance
• Constipation
• Dry skin
• Hair loss
• Bradycardia
• Depression
• Memory impairment
• Muscle aches and weakness
• Hoarseness
• Puffiness in face/eyes
• Menstrual irregularities (in women)
• Nervousness
• Palpitations
• Tremor
• Heat intolerance
• Diarrhea
• Weight loss (unintended)
• Insomnia

Levothyroxine is Category A. Thyroid hormone requirements often increase during pregnancy. It is crucial to continue levothyroxine therapy and monitor TSH levels frequently (e.g., every 4-6 weeks) to ensure adequate thyroid hormone replacement for both maternal and fetal health. Untreated maternal hypothyroidism can lead to adverse pregnancy outcomes.

Levothyroxine is compatible with breastfeeding (L1 - Safest). Minimal amounts are excreted into breast milk, and it does not adversely affect the nursing infant. It is essential for the mother's health and does not pose a risk to the infant.

Dosing is highly individualized based on age, weight, and TSH levels. Oral administration is preferred for chronic therapy. IV levothyroxine is reserved for severe cases (e.g., myxedema coma) or when oral administration is not possible. Careful monitoring of growth, development, and thyroid function is essential.

Elderly patients may be more sensitive to the effects of levothyroxine, particularly cardiovascular effects. Lower initial doses and slower titration are recommended. Close monitoring for cardiac symptoms is crucial.

• Levothyroxine IV is primarily used for patients unable to take oral medication or in emergency situations like myxedema coma.
• The IV dose is typically 50% of the patient's usual oral maintenance dose due to 100% bioavailability.
• For myxedema coma, a large loading dose is often given, followed by daily maintenance.
• Always assess for adrenal insufficiency before initiating thyroid hormone replacement, especially in myxedema coma, to avoid precipitating an adrenal crisis.
• Monitor TSH and Free T4 levels closely, as well as clinical symptoms, to guide dose adjustments.
• Be cautious when administering to patients with pre-existing cardiovascular disease; start low and titrate slowly.
• Many drugs can interact with levothyroxine, affecting its absorption, metabolism, or protein binding. Review concomitant medications carefully.

• Liothyronine (T3) injection (e.g., Triostat) - used in specific situations, often in combination with levothyroxine for myxedema coma, due to its faster onset and shorter half-life.
• Oral levothyroxine (e.g., Synthroid, Levoxyl, Unithroid) - the standard long-term treatment for hypothyroidism.

If your symptoms or health problems persist or worsen, it is essential to contact your doctor for further guidance. To ensure safe use, never share your medication with others, and do not take medication prescribed for someone else. 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. If you are unsure about the proper disposal method, consult your pharmacist, who can also inform you about potential drug take-back programs in your area. Some medications may come with an additional patient information leaflet, which your pharmacist can provide. If you have any questions or concerns about your 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 emergency medical attention. Be prepared to provide information about the medication taken, the amount, and the time it was taken to ensure prompt and effective treatment.