Thyrox
Generic Name
Levothyroxine Sodium
Manufacturer
Sanofi India Ltd.
Country
India
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Price Details
Current market pricing information
| Variant | Unit Price | Strip Price |
|---|---|---|
| thyrox 50 mcg tablet | ৳ 2.20 | N/A |
Description
Overview of the medicine
Thyrox-50 mcg tablet contains Levothyroxine Sodium, a synthetic thyroid hormone used to treat hypothyroidism and to suppress TSH in certain thyroid cancers. It replaces the thyroid hormone that your body naturally produces.
Uses & Indications
Dosage
Adults
Initial dose typically 25-50 mcg orally once daily, adjusted in 12.5-25 mcg increments every 4-6 weeks based on TSH levels. Maintenance dose usually 75-125 mcg/day.
Elderly
Lower initial doses (e.g., 12.5-25 mcg/day) are recommended due to increased sensitivity to thyroid hormones and potential cardiovascular comorbidities. Gradual dose titration.
Renal_impairment
No dosage adjustment required; levothyroxine is minimally excreted renally.
How to Take
Take orally once daily, preferably on an empty stomach 30-60 minutes before breakfast. Do not take with food or other medications (especially antacids, iron, calcium) within 4 hours, as they can impair absorption.
Mechanism of Action
Levothyroxine acts as a synthetic form of thyroxine (T4) and is converted to its active metabolite, liothyronine (T3), in the body. T3 and T4 bind to thyroid hormone receptors in the cell nucleus, initiating gene transcription and protein synthesis, regulating metabolism, growth, and development.
Pharmacokinetics
Onset
Initial effects may be seen within 3-5 days, but full therapeutic effect may take 4-6 weeks.
Excretion
Mainly excreted via the bile into the feces. A small amount is excreted renally.
Half life
Approximately 6-7 days (euthyroid patients), but can be longer in hypothyroid patients and shorter in hyperthyroid patients.
Absorption
Variably absorbed from the gastrointestinal tract (40-80%), primarily in the small intestine. Absorption is influenced by food, gastric acidity, and other medications.
Metabolism
Primarily metabolized in the liver, kidney, and other tissues by deiodination to T3 and reverse T3 (rT3), and by conjugation with sulfates and glucuronides.
Side Effects
Contraindications
- Untreated subclinical or overt hyperthyroidism
- Acute myocardial infarction
- Acute myocarditis
- Uncorrected adrenal insufficiency
Drug Interactions
Warfarin
May increase the anticoagulant effect of warfarin. INR monitoring required.
Oral contraceptives (estrogen)
May increase thyroid-binding globulin, requiring higher levothyroxine dose.
Cholestyramine, Colestipol, Sevelamer
May bind levothyroxine and reduce absorption. Separate administration by at least 4-5 hours.
Antacids (aluminum/magnesium), Iron, Calcium supplements
May decrease levothyroxine absorption. Separate administration by at least 4 hours.
Storage
Store below 30°C in a dry place, away from light and moisture. Keep out of reach of children.
Overdose
Symptoms of overdose include signs of hyperthyroidism: palpitations, tachycardia, arrhythmias, sweating, tremors, anxiety, insomnia, weight loss, fever, diarrhea. Management involves symptomatic and supportive care, reduction or temporary discontinuation of the drug. Beta-blockers may be used for cardiovascular symptoms.
Pregnancy & Lactation
Levothyroxine is generally considered safe and essential during pregnancy and lactation. Thyroid hormone requirements usually increase during pregnancy. Regular TSH monitoring and dose adjustments are necessary. Levothyroxine is minimally secreted into breast milk and has no adverse effects on the infant.
Side Effects
Contraindications
- Untreated subclinical or overt hyperthyroidism
- Acute myocardial infarction
- Acute myocarditis
- Uncorrected adrenal insufficiency
Drug Interactions
Warfarin
May increase the anticoagulant effect of warfarin. INR monitoring required.
Oral contraceptives (estrogen)
May increase thyroid-binding globulin, requiring higher levothyroxine dose.
Cholestyramine, Colestipol, Sevelamer
May bind levothyroxine and reduce absorption. Separate administration by at least 4-5 hours.
Antacids (aluminum/magnesium), Iron, Calcium supplements
May decrease levothyroxine absorption. Separate administration by at least 4 hours.
Storage
Store below 30°C in a dry place, away from light and moisture. Keep out of reach of children.
Overdose
Symptoms of overdose include signs of hyperthyroidism: palpitations, tachycardia, arrhythmias, sweating, tremors, anxiety, insomnia, weight loss, fever, diarrhea. Management involves symptomatic and supportive care, reduction or temporary discontinuation of the drug. Beta-blockers may be used for cardiovascular symptoms.
Pregnancy & Lactation
Levothyroxine is generally considered safe and essential during pregnancy and lactation. Thyroid hormone requirements usually increase during pregnancy. Regular TSH monitoring and dose adjustments are necessary. Levothyroxine is minimally secreted into breast milk and has no adverse effects on the infant.
Frequently Asked Questions
Common questions about this medicine
Pack Sizes
Shelf Life
Typically 2-3 years from manufacturing date, refer to packaging for exact expiry.
Availability
Pharmacies, hospitals, clinics
Approval Status
Approved by health authorities worldwide (e.g., FDA, DGDA)
Patent Status
Generic (off-patent)
WHO Essential Medicine
YesClinical Trials
Levothyroxine has been extensively studied in numerous clinical trials establishing its efficacy and safety for thyroid hormone replacement and TSH suppression.
Lab Monitoring
- Thyroid Stimulating Hormone (TSH) levels (primary monitoring parameter)
- Free T4 levels
- Symptoms of hyperthyroidism or hypothyroidism
Doctor Notes
- Emphasize consistent daily dosing and strict adherence to administration instructions (empty stomach).
- Regular TSH monitoring is crucial for dose adjustment.
- Advise patients about potential drug and food interactions, especially with calcium, iron, and antacids.
Patient Guidelines
- Take at the same time each day, preferably on an empty stomach.
- Do not stop taking the medicine without consulting your doctor.
- Avoid taking with calcium, iron supplements, antacids, or certain foods within 4 hours.
- Report any signs of hyperthyroidism (e.g., rapid heartbeat, sweating, anxiety) to your doctor.
Missed Dose Advice
If a dose is missed, take it as soon as you remember, unless it is almost time for your next dose. Do not double the dose to catch up. If multiple doses are missed, consult your doctor.
Driving Precautions
Levothyroxine typically does not impair the ability to drive or operate machinery. However, if side effects like tremors or anxiety occur, exercise caution.
Lifestyle Advice
- Maintain a balanced diet.
- Engage in regular physical activity.
- Manage stress effectively.
- Avoid sudden changes in diet or supplements without consulting a doctor.
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