Medithyrox (Levothyroxine Sodium)

Medithyrox is a synthetic thyroid hormone that restores normal hormone levels in conditions affecting thyroid function.

• Hypothyroidism: normalizes metabolic rate and alleviates fatigue, weight gain, and cold intolerance.
• Post‑thyroidectomy replacement: provides necessary hormone after surgical removal of the thyroid gland.
• Goiter: reduces gland size by correcting hormone deficiency.
• Congenital hypothyroidism: supports growth and neurodevelopment in affected infants.

• Levothyroxine Sodium is a synthetic form of thyroxine (T4) that is absorbed into the bloodstream after oral administration. It binds to nuclear thyroid hormone receptors in target cells, modulating gene transcription that increases basal metabolic rate, promotes protein synthesis, and supports normal growth and development. By restoring circulating T4 levels, it compensates for endogenous thyroid hormone deficiency.

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

Common Side Effects

• Headache: mild to moderate pain often occurring early in therapy.
• 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

• Cardiac arrhythmia: irregular heart rhythm that may require medical attention.
• Angina pectoris: chest pain due to reduced blood flow to the heart.
• Myocardial infarction: heart attack in susceptible patients.
• Severe allergic reaction: rash, swelling, or difficulty breathing.
• Bone loss (osteoporosis): decreased bone mineral density with long‑term overtreatment.
• Adrenal crisis: precipitated in patients with untreated adrenal insufficiency.

When prescribing Medithyrox, clinicians should consider several safety measures.

• Dose adjustment in elderly: start with lower doses and titrate slowly.
• Monitor thyroid function: regularly check TSH and free T4 levels.
• Cardiovascular disease caution: assess risk of angina or arrhythmias before dose increases.
• Avoid use in untreated adrenal insufficiency: may precipitate adrenal crisis.
• Do not discontinue abruptly: taper under medical supervision to prevent hypothyroid rebound.
• Store at room temperature: keep in the original container, protect from moisture and light.

Levothyroxine absorption and activity can be altered by several concomitant medicines.

Major Interactions (Avoid)

• Calcium supplements: bind levothyroxine and reduce its absorption.
• Iron preparations: significantly decrease oral bioavailability.
• Antacids containing aluminum or magnesium: impair absorption when taken simultaneously.
• Amiodarone: may increase thyroid hormone levels and require dose adjustment.
• Warfarin: levothyroxine can enhance anticoagulant effect, necessitating INR monitoring.

Moderate Interactions (Monitor Closely)

• Cholesterol‑lowering agents (e.g., cholestyramine): may lower levothyroxine levels.
• Antidepressants (SSRIs): can affect thyroid hormone metabolism.
• Diabetes medications: altered thyroid status may influence glucose control.