Indications 

Levothyroxine is a medication prescribed for the treatment of hypothyroidism, a condition characterized by an underactive thyroid gland. It functions by replacing or supplementing the deficient thyroid hormone, which is typically produced by the thyroid gland. Hypothyroidism can occur naturally or result from thyroid gland injury due to radiation, medications, or surgical removal.  

Adequate levels of thyroid hormone are crucial for maintaining optimal mental and physical activity. In children, sufficient thyroid hormone is essential for normal mental and physical development. Levothyroxine is utilized for managing various thyroid disorders, including thyroid cancer. However, it should not be employed for infertility treatment unless low thyroid hormone levels are identified as the underlying cause. 

Uses and Dosage 

Follow these instructions for taking this medication: 

• Take the medication orally as prescribed by your doctor, usually once a day on an empty stomach, 30 minutes to 1 hour before breakfast. 
• Swallow the capsule form of the medication whole; do not split, crush, or chew it. 
• If you or your child cannot swallow the capsule, use the tablet form of the medication instead. 
• For infants or children who cannot swallow whole tablets, crush the tablet and mix it with 1 to 2 teaspoons (5 to 10 milliliters) of water. Administer the mixture using a spoon or dropper immediately. Avoid preparing the mixture in advance or mixing the tablet with soy infant formula. Consult your pharmacist for further guidance. 
• The dosage of the medication is determined based on factors such as your age, weight, medical condition, laboratory test results, response to treatment, and other medications you may be taking. Inform your doctor and pharmacist about all the products you are using, including prescription drugs, nonprescription drugs, and herbal products. 
• Use this medication regularly to obtain the maximum benefit. To help you remember, take it at the same time each day. 

Side Effects 

While taking levothyroxine (Eltroxin), you may experience certain side effects. Although not all of these side effects are common, be aware of them and seek medical attention if they occur. Contact your doctor immediately if you experience any of the following side effects: 

Less Common Side Effects  

• Chest pain, discomfort, or tightness 
• Decreased urine output 
• Difficult or labored breathing 
• Difficulty with swallowing 
• Dilated neck veins 
• Extreme fatigue 
• Fainting 
• Fast, slow, irregular, pounding, or racing heartbeat or pulse 
• Fever 
• Heat intolerance 
• Hives or welts, skin itching, rash, or redness 
• Irregular breathing 
• Irritability 
• Menstrual changes 
• Nausea 
• Pain or discomfort in the arms, jaw, back, or neck 
• Sweating 
• Swelling of the eyes, face, lips, throat, or tongue 
• Tremors 

Rare Side Effects  

• Blurred or double vision 
• Dizziness 
• Eye pain 
• Lack or slowing of normal growth in children 
• Limp or favoring one leg while walking 
• Pain in the hip or knee 
• Seizures 
• Severe headache 

Cautions 

Prior to using this medication, inform your doctor or pharmacist about your medical history, particularly if you have any of the following conditions: increased thyroid hormones (thyrotoxicosis), decreased adrenal gland function, heart disease (such as coronary artery disease, irregular heartbeat), high blood pressure, or diabetes. 

If you have diabetes, monitor your blood sugar regularly as directed and share the results with your doctor. This medication may affect your blood sugar levels. Promptly inform your doctor if you experience symptoms such as increased thirst/urination, shakiness, unusual sweating, dizziness, or hunger. Your doctor may need to adjust your diabetes medication, exercise program, or diet accordingly. 

Before undergoing surgery, disclose to your doctor or dentist all the products you are using, including prescription drugs, nonprescription drugs, and herbal products. This information will help ensure a safe and effective surgical procedure. 

Children may be more susceptible to certain side effects of this drug, such as headache, vision changes, and hip/leg pain. Elevated thyroid hormone levels can potentially affect bone development and growth, leading to a reduced final adult height. Attend all scheduled lab and medical appointments so that your doctor can closely monitor the treatment and its effects.