Levothyroxine sodium

Levothyroxine sodium is a synthetic form of thyroxine (T4), a hormone secreted by the thyroid gland. It is primarily used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormones. Levothyroxine sodium works by replacing the missing thyroxine, thus normalizing the body's metabolic rate and alleviating the symptoms associated with hypothyroidism.

Indications

Levothyroxine sodium is indicated for the treatment of hypothyroidism of any etiology, including congenital hypothyroidism in newborns, primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism. It is also used in the management of thyroid cancer to suppress thyrotropin (TSH) secretion. Additionally, it is employed in the TSH suppression test to diagnose suspected hyperthyroidism or thyroid gland autonomy.

Pharmacology

Levothyroxine sodium acts by replacing the deficient thyroxine hormone in the body. Thyroxine is responsible for regulating the body's energy and metabolism. Once absorbed, levothyroxine is converted to triiodothyronine (T3), the active form of thyroid hormone, in the liver and kidneys. This conversion is necessary for the medication to exert its physiological effects.

Dosage and Administration

The dosage of levothyroxine sodium is highly individualized based on the patient's age, body weight, cardiovascular status, and the nature and severity of the condition being treated. It is typically started at a low dose, especially in elderly patients and those with cardiovascular conditions, with gradual increments until the desired therapeutic effect is achieved.

Side Effects

Common side effects of levothyroxine sodium include, but are not limited to, increased heart rate, heart palpitations, nervousness, headache, muscle weakness, and weight loss. Excessive doses can lead to symptoms of hyperthyroidism, including increased appetite, insomnia, heat intolerance, and sweating.

Interactions

Levothyroxine sodium's absorption can be affected by certain foods and medications. For instance, calcium and iron supplements, as well as some cholesterol-lowering drugs, can decrease the absorption of levothyroxine. Therefore, it is recommended to take levothyroxine on an empty stomach, at least 30 to 60 minutes before breakfast or at least 3 to 4 hours after dinner.

Precautions

Patients with underlying cardiovascular diseases should be monitored closely as levothyroxine can increase heart rate and blood pressure. Dose adjustments may be necessary in patients with severe long-standing hypothyroidism, as rapid correction of the condition can precipitate acute myocardial infarction or arrhythmias.

Conclusion

Levothyroxine sodium is a vital medication in the management of hypothyroidism and other conditions requiring thyroid hormone replacement or suppression. Its use must be carefully monitored to avoid adverse effects and interactions with other medications.