Levothyroxine Mercury Pharma Group (Anhydrous Levothyroxine Sodium)

• Levothyroxine is a thyroid hormone replacement that restores normal metabolic function in hypothyroid conditions.
• Primary hypothyroidism: normalizes thyroid hormone levels and alleviates symptoms such as fatigue and weight gain.
• Secondary hypothyroidism: provides necessary hormone replacement when pituitary dysfunction reduces TSH production.
• Post‑thyroidectomy: supplies thyroxine to patients who have had their thyroid gland removed, maintaining metabolic stability.
• Goitre management: helps reduce gland enlargement by correcting hormone deficiency.

• Levothyroxine is a synthetic form of the endogenous hormone thyroxine (T4). After oral absorption, it enters the bloodstream and is converted to the active hormone triiodothyronine (T3) within peripheral tissues. Both T4 and T3 bind to nuclear thyroid hormone receptors, modulating gene transcription that increases basal metabolic rate, influences protein synthesis, and supports growth and development.

Levothyroxine may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Headache: mild headache reported especially during dose adjustments.
• Insomnia: difficulty sleeping or altered sleep patterns.
• Palpitations: sensation of rapid or irregular heartbeat.
• Weight loss: unintended reduction in body weight.

Serious or Rare Side Effects

• Cardiac arrhythmia: potentially life‑threatening irregular heart rhythm.
• Angina or myocardial infarction: chest pain or heart attack in susceptible patients.
• Osteoporosis: decreased bone mineral density with long‑term overtreatment.
• Severe allergic reaction: rash, itching, swelling, or anaphylaxis.

When prescribing levothyroxine, clinicians should consider several safety precautions to minimize risks.

• Dose titration: start with a low dose and adjust based on thyroid function tests.
• Cardiovascular disease: monitor patients with coronary artery disease for chest pain or arrhythmias.
• Pregnancy and lactation: use the lowest effective dose and monitor maternal thyroid status closely.
• Elderly patients: initiate therapy at reduced doses due to altered metabolism.
• Drug monitoring: regularly check serum TSH and free T4 levels to ensure appropriate dosing.
• Store at ambient temperature: keep tablets below 25 °C in the original container, protected from moisture and light.

Levothyroxine’s absorption and activity can be affected by several concomitant medicines.

Major Interactions (Avoid)

• Calcium supplements: bind levothyroxine in the gut, reducing absorption.
• Iron salts: significantly decrease oral bioavailability when taken together.
• Sucralfate: forms complexes that impair levothyroxine uptake.
• Cholestyramine and other bile‑acid sequestrants: lower serum hormone levels.
• Antacids containing aluminum or magnesium: interfere with absorption.

Moderate Interactions (Monitor Closely)

• Warfarin: levothyroxine may enhance anticoagulant effect, requiring INR monitoring.
• Oral contraceptives: may increase thyroxine binding, altering dose requirements.
• Amiodarone: can affect thyroid hormone metabolism and necessitate dose adjustments.
• Beta‑blockers: may mask symptoms of hyperthyroidism.
• SSRIs: may influence thyroid hormone levels, requiring periodic testing.