L-Thyroxin Berlin-Chemie (Levothyroxine Sodium Pentahydrate)

Levothyroxine sodium is used to restore normal thyroid hormone levels in conditions affecting the thyroid gland.

• Hypothyroidism: normalises metabolic rate and alleviates symptoms such as fatigue and weight gain.
• Thyroid hormone replacement therapy after thyroidectomy or radioactive iodine: provides the missing thyroxine hormone.
• Goitre: reduces gland enlargement by correcting hormone deficiency.

• Levothyroxine sodium is a synthetic analogue 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, regulating gene transcription that controls basal metabolic rate, protein synthesis, and growth, thereby restoring normal physiological function in hypothyroid states.

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

Common Side Effects

• Headache: mild to moderate intensity.
• Insomnia: difficulty falling or staying asleep.
• Palpitations: sensation of rapid or irregular heartbeat.
• Weight loss: unintended reduction in body weight.
• Heat intolerance: increased sensitivity to warm environments.
• Tremor: fine shaking of hands or limbs.

Serious or Rare Side Effects

• Chest pain: possible sign of cardiac ischemia.
• Arrhythmia: abnormal heart rhythm, especially in high doses.
• Allergic reaction: rash, itching, swelling, or anaphylaxis.
• Angioedema: rapid swelling of face, lips, or throat.
• Severe bone loss: increased risk of osteoporosis with long‑term overtreatment.

Levothyroxine requires careful monitoring and patient education to minimise risks.

• Thyroid function monitoring: regularly check TSH and free T4 levels to adjust dose.
• Dose adjustment in the elderly: start with lower doses to avoid cardiac stress.
• Cardiovascular disease caution: assess heart condition before initiating therapy.
• Avoid abrupt discontinuation: taper under medical supervision to prevent hypothyroid crisis.
• Pregnancy and lactation: use only if clearly needed and under physician guidance.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Levothyroxine may interact with several medicines, altering its absorption or effect.

Major Interactions (Avoid)

• Antacids containing aluminum or magnesium: reduce levothyroxine absorption.
• Calcium supplements: bind levothyroxine in the gut, decreasing bioavailability.
• Iron supplements: interfere with absorption when taken concurrently.
• Cholestyramine or other bile‑acid sequestrants: markedly lower levothyroxine levels.
• Sucralfate: forms complexes that impede absorption.

Moderate Interactions (Monitor Closely)

• Amiodarone: may affect thyroid hormone metabolism.
• Estrogen therapy or oral contraceptives: can increase levothyroxine requirement.
• Carbamazepine and phenytoin: induce hepatic enzymes, lowering levothyroxine levels.
• Rifampin: accelerates metabolism, potentially reducing efficacy.
• Warfarin: levothyroxine may enhance anticoagulant effect, requiring INR monitoring.