| Recommended Dose and Dosage Regimen | The recommended starting dose of levothyroxine for hypothyroidism in adults is usually 25-50 mcg once daily. The dosage may be adjusted based on the patient’s age, weight, underlying thyroid condition, and response to treatment, with increments of 25-50 mcg every 4-6 weeks until the desired thyroid function is achieved. Maintenance doses typically range from 50-200 mcg once daily. Follow your healthcare provider’s instructions regarding dosing. |
| Frequency of Administration | Levothyroxine is usually taken once daily, preferably in the morning on an empty stomach, at least 30 minutes to 1 hour before breakfast. |
| Route of Administration | Levothyroxine is administered orally in the form of tablets or capsules. |
| Mechanism of Action (MOA) | Levothyroxine is a synthetic form of thyroxine (T4), a thyroid hormone. It acts as a replacement for endogenous T4, restoring thyroid hormone levels in patients with hypothyroidism. Levothyroxine is converted to triiodothyronine (T3) in peripheral tissues, where it regulates metabolic processes, growth, and development. |
| Pharmacokinetics (PK) | Levothyroxine is well absorbed after oral administration, with peak plasma concentrations occurring within 2-4 hours. Absorption may be affected by various factors, including gastrointestinal motility, food, and other medications. It has a long elimination half-life of approximately 6-7 days, necessitating once-daily dosing for steady-state levels. |
| Pharmacodynamics (PD) | Levothyroxine exerts its pharmacodynamic effects by replacing deficient or absent thyroid hormone, thereby restoring metabolic function, energy levels, and overall well-being in patients with hypothyroidism. It regulates gene transcription and protein synthesis in target tissues throughout the body. |
| Pathophysiology | Levothyroxine is used in the management of hypothyroidism, a condition characterized by insufficient thyroid hormone production by the thyroid gland. Hypothyroidism may result from various etiologies, including autoimmune thyroiditis (Hashimoto’s thyroiditis), thyroid surgery, radioactive iodine therapy, and congenital thyroid disorders. |
| Primary Indications | Hypothyroidism (primary and secondary). |
| Contraindications | Contraindications to levothyroxine use include hypersensitivity to levothyroxine or its components, untreated thyrotoxicosis, acute myocardial infarction, and uncorrected adrenal insufficiency. Use caution in patients with cardiovascular disease, diabetes mellitus, and adrenal insufficiency. |
| Purpose of Taking Medication | The purpose of levothyroxine therapy is to replace deficient or absent thyroid hormone, restoring normal metabolic function and alleviating symptoms associated with hypothyroidism, such as fatigue, weight gain, cold intolerance, and depression. |
| Usage Instructions | Take levothyroxine exactly as prescribed by your healthcare provider. It is usually taken as a single daily dose in the morning, on an empty stomach, with water, at least 30 minutes to 1 hour before breakfast or other medications. Avoid taking levothyroxine with calcium supplements, iron supplements, or certain antacids, as they may interfere with absorption. |
| Precautions and Care | Patients taking levothyroxine should be monitored regularly for thyroid function tests, including serum thyroid-stimulating hormone (TSH) levels. Dosage adjustments may be necessary based on clinical response and laboratory results. Avoid abrupt discontinuation of therapy, as it may lead to recurrence of hypothyroidism symptoms. |
| Dietary Considerations | Levothyroxine absorption may be affected by dietary factors, including fiber, soy, and certain medications. Take levothyroxine consistently with regard to meals and other medications to maintain stable thyroid hormone levels. |
| Missed Dose | If a dose of levothyroxine is missed, take it as soon as you remember, unless it is almost time for your next dose. Do not double the dose to catch up. |
| Possible Side Effects | Common side effects of levothyroxine may include palpitations, tachycardia, weight loss, insomnia, heat intolerance, and gastrointestinal disturbances. Overreplacement may lead to thyrotoxicosis or exacerbation of cardiovascular symptoms. |
| Storage and Disposal | Store levothyroxine tablets at room temperature away from light and moisture. Keep the medication in its original packaging and out of reach of children and pets. Dispose of unused or expired medication according to local regulations. |
| Overdose or Emergency | In case of overdose, seek emergency medical attention or contact a poison control center immediately. Symptoms may include tachycardia, chest pain, tremors, agitation, confusion, and seizures. |
| Monitoring and Laboratory Tests | Patients taking levothyroxine may require regular monitoring of thyroid function tests, including serum TSH levels. Additional laboratory tests may be performed based on individual clinical needs and risk factors. |
