Levothyroxine Natrium Uni-Pharma (Levothyroxine Sodium)

Levothyroxine Sodium is used to treat disorders of thyroid hormone deficiency and related metabolic conditions.

• Hypothyroidism: normalises low thyroid hormone levels and alleviates fatigue, weight gain and cold intolerance.
• Post‑thyroidectomy replacement: provides the missing thyroxine after surgical removal of the thyroid gland.
• Goitre: reduces gland enlargement by supplying adequate hormone feedback.

• Levothyroxine Sodium is a synthetic form of the endogenous hormone thyroxine (T4). After oral absorption, it is converted to the active hormone triiodothyronine (T3) in peripheral tissues. The hormone binds nuclear thyroid receptors, modulating gene transcription that regulates basal metabolic rate, protein synthesis, and growth. By restoring circulating T4, the drug re‑establishes normal feedback to the hypothalamic‑pituitary‑thyroid axis, normalising thyroid‑stimulating hormone (TSH) secretion.

Levothyroxine Sodium may cause a range of adverse reactions, most of which are dose‑related.

Common Side Effects

• Headache: mild to moderate discomfort often reported during dose adjustments.
• Insomnia: difficulty falling or staying asleep, especially with higher doses.
• Palpitations: sensation of rapid or irregular heartbeat.
• Heat intolerance: increased sensitivity to warm environments.
• Tremor: fine shaking of hands or limbs.
• Weight loss: unintended reduction in body weight.

Serious or Rare Side Effects

• Cardiac arrhythmia: irregular heart rhythm that may require medical attention.
• Angina pectoris: chest pain due to reduced coronary blood flow.
• Myocardial infarction: rare but possible in susceptible individuals.
• Severe bone loss: accelerated osteoporosis with long‑term overtreatment.
• Anaphylaxis: rare allergic reaction with rash, swelling, or breathing difficulty.
• Acute adrenal crisis: precipitated in patients with untreated adrenal insufficiency.

Levothyroxine Sodium requires careful clinical monitoring to avoid over‑ or under‑replacement.

• Dose titration: adjust gradually, especially in elderly or cardiac patients.
• Thyroid function monitoring: check TSH and free T4 levels regularly after dose changes.
• Cardiovascular risk: use caution in patients with ischemic heart disease or arrhythmias.
• Adrenal insufficiency: ensure adequate glucocorticoid replacement before initiating levothyroxine.
• Pregnancy and lactation: discuss risks with a healthcare professional; dosing may need adjustment.
• Store at ambient temperature: keep below 25 °C, in the original container, protected from moisture and light.

Levothyroxine Sodium can interact with several medicines, altering its absorption or pharmacodynamic effect.

Major Interactions (Avoid)

• Calcium supplements: bind levothyroxine in the gut, reducing absorption.
• Iron salts: significantly decrease oral bioavailability when taken concurrently.
• Antacids containing aluminum or magnesium: impair absorption if taken within 4 hours.
• Cholestyramine and other bile‑acid sequestrants: lower systemic exposure.
• Sucralfate: forms insoluble complexes, decreasing effectiveness.

Moderate Interactions (Monitor Closely)

• Warfarin: levothyroxine may enhance anticoagulant effect, requiring INR monitoring.
• Oral contraceptives: may increase levothyroxine binding proteins, altering dose needs.
• Amiodarone: affects thyroid hormone metabolism, necessitating closer TSH checks.
• Beta‑blockers: may mask symptoms of thyrotoxicosis.
• Diabetes medications: thyroid status influences glucose control, requiring dose adjustments.