Generic
Levothyroxine Sodium
36 brands available in the market
At a glance
Levothyroxine Sodium is a medicine used to treat an underactive thyroid gland (hypothyroidism). It replaces the hormone which was not being produced by your thyroid gland in sufficient quantity and helps regulate your body's energy and metabolism.
Description
Levothyroxine Sodium is a synthetic Levothyroxine (Thyroxine or T4) which is identical to the natural hormone T4 produced in the thyroid gland. About 30% of T4 is converted to the much more active Triiodothyronine (T3) in peripheral tissues. TBG (Thyroxine Binding Globulin) is the major carrier of T4. This binding protects T4 from metabolism and excretion resulting in its long half-life in the circulation. The half-life of elimination of T4 is 6 to 7 days.
Indications
- Hypothyroidism - replacement therapy of any etiology
- Suppression of Thyroid Stimulating Hormone (TSH) levels - goitres, nodules, and after treatment of thyroid cancer
- Suppression of goitrogenic effects of other drugs (e.g., lithium)
- Diagnostic aid in suppression tests
Therapeutic class
Thyroid Drugs & Hormones
Pharmacological class
Thyroxine Analog
Pharmacology
Levothyroxine Sodium is a synthetic thyroxine identical to natural T4. It increases basal metabolic rate (BMR) and utilization and mobilization of glycogen stores and stimulates protein synthesis. These effects are mediated at the cellular level by the thyroxine metabolite, tri-iodothyronine (T3).
Mechanism of action
Replaces thyroid hormone to relieve symptoms of hypothyroidism.
Dosage
Adult Dose (Oral):
- Mild Hypothyroidism: 1.7 mcg/kg or 100-125 mcg daily; max 300 mcg/day
- >50 years or with CVD: 12.5-25 mcg daily start; adjust 12.5-25 mcg every 4-6 weeks
- Severe Hypothyroidism: 12.5-25 mcg daily start; increase 25 mcg every 2-4 weeks
- TSH suppression in thyroid cancer: >2 mcg/kg/day
Pediatric Dose: 0-3 months: 10-15 mcg/kg/day; 3-6 months: 8-10; 6-12 months: 6-8; 1-5 years: 5-6; 6-12 years: 4-5; >12 years: 2-3 mcg/kg/day
Administration
- Swallow tablet whole; do not chew, crush or break
- Take on an empty stomach (first thing in the morning)
- No food 1 hour before and 2 hours after taking
- Take at the same time each day
Missed dose
If you miss a dose, take it as soon as possible. If it's almost time for your next dose, skip the missed dose and go back to your regular schedule. Do not double the dose.
Side effects
Common Side Effects (due to overdose):
- Palpitations
- Vomiting
- Anxiety
- Diarrhea
- Flushing
- Weight loss
- Nervousness
- Restlessness
Precautions & warnings
- Monitor thyroid hormone levels regularly
- Dose adjustment needed with weight changes
- Maintain 4-hour gap with antacids, calcium, or iron supplements
- Inform doctor before changing brand
- Dose may need to be increased during pregnancy
Contraindications
- Untreated hyperthyroidism
- Uncorrected adrenal failure
- Recent myocardial infarction
Drug interactions
- Iron, antacids, cholestyramine, calcium carbonate, sucralfate reduce absorption
- Amiodarone and propranolol reduce T3 levels
- Carbamazepine, phenytoin, rifampicin reduce T4 levels
- May alter requirements of antidiabetic drugs
- May increase anticoagulant effect of warfarin
Food interactions
Alcohol consumption with Levothyroxine Sodium is safe.
Use in pregnancy
Use in Pregnancy: Levothyroxine Sodium is safe during pregnancy (Category A). Low or no risk to the developing baby. Dose may need to be increased during pregnancy.
Pregnancy Category: A — always consult a doctor before taking during pregnancy.
Use in lactation
Use in Lactation: Levothyroxine Sodium is safe during breastfeeding; does not pass into breastmilk in significant amounts.
Pediatric use
Pediatric doses are established (age and weight-based); doses established for neonates.
Geriatric use
Dose adjustment needed in elderly (start with lower dose due to cardiac risk).
Renal / hepatic impairment
Renal Impairment: Limited information available; consult your doctor.
Hepatic Impairment: Limited information available; consult your doctor.
Overdose effects
Overdose symptoms: agitation, confusion, irritability, hyperactivity, headache, sweating, tachycardia, arrhythmias, coma. Symptomatic treatment.
Storage conditions
Store below 30°C in a dry place, protected from light; keep out of reach of children.
Chemical structure
Levothyroxine Sodium