Thyrox
Generic Name
Levothyroxine Sodium
Manufacturer
Macleods Pharmaceuticals
Country
India
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Price Details
Current market pricing information
| Variant | Unit Price | Strip Price |
|---|---|---|
| thyrox 100 mcg tablet | ৳ 3.10 | N/A |
Description
Overview of the medicine
Thyrox-100 mcg tablet contains Levothyroxine Sodium, a synthetic thyroid hormone used to treat an underactive thyroid gland (hypothyroidism) and certain types of thyroid cancer. It replaces the natural hormone thyroxine, which is essential for normal physical and mental development and metabolism.
Uses & Indications
Dosage
Adults
Initial dose typically 25-50 mcg daily, adjusted by 12.5-25 mcg increments every 4-6 weeks based on TSH levels. Maintenance dose usually 100-200 mcg daily.
Elderly
Lower initial doses (12.5-25 mcg daily) and slower titration are recommended due to increased risk of cardiac side effects.
Renal_impairment
No specific dosage adjustment required, as levothyroxine is not primarily renally excreted.
How to Take
Oral, once daily, preferably on an empty stomach 30-60 minutes before breakfast. It should be taken with a full glass of water.
Mechanism of Action
Levothyroxine acts as a synthetic replacement for endogenous thyroxine (T4). It is converted to its active metabolite, liothyronine (T3), which then binds to thyroid hormone receptors in the cell nucleus. This binding stimulates gene expression and protein synthesis, regulating various metabolic processes, including growth, energy metabolism, and tissue development.
Pharmacokinetics
Onset
Clinical effects are usually seen within 3-5 days; full therapeutic effect may take several weeks.
Excretion
Primarily renal (approximately 80%), with a smaller amount eliminated via bile in feces.
Half life
6-7 days (euthyroid individuals); can be longer in hypothyroidism and shorter in hyperthyroidism.
Absorption
Approximately 40-80% absorbed, primarily from the small intestine. Absorption can be affected by food and other medications.
Metabolism
Primarily deiodination in the liver and kidneys to T3 and reverse T3 (rT3), followed by conjugation and enterohepatic recirculation.
Side Effects
Contraindications
- Untreated thyrotoxicosis
- Acute myocardial infarction
- Acute myocarditis
- Acute panhypopituitarism (unless adrenal insufficiency is corrected)
- Hypersensitivity to levothyroxine or any excipients
Drug Interactions
Warfarin
Levothyroxine may increase the anticoagulant effect of warfarin; monitor INR.
Amiodarone
May alter thyroid function.
Beta-blockers
May reduce conversion of T4 to T3.
Proton pump inhibitors
May decrease levothyroxine absorption.
Antacids, iron, calcium supplements
Decrease levothyroxine absorption. Separate administration by at least 4 hours.
Estrogens (e.g., oral contraceptives)
May increase levothyroxine requirements.
Bile acid sequestrants (e.g., cholestyramine)
Decrease levothyroxine absorption. Separate by 4-6 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 may include fever, insomnia, tremors, palpitations, anxiety, sweating, weight loss, and diarrhea. Management involves symptomatic and supportive treatment. Beta-blockers may be used to control cardiovascular symptoms.
Pregnancy & Lactation
Pregnancy Category A. Levothyroxine is essential for fetal neurological development. Dosage requirements may increase during pregnancy. It is generally considered safe during lactation; small amounts are excreted in breast milk but are not known to adversely affect the infant.
Side Effects
Contraindications
- Untreated thyrotoxicosis
- Acute myocardial infarction
- Acute myocarditis
- Acute panhypopituitarism (unless adrenal insufficiency is corrected)
- Hypersensitivity to levothyroxine or any excipients
Drug Interactions
Warfarin
Levothyroxine may increase the anticoagulant effect of warfarin; monitor INR.
Amiodarone
May alter thyroid function.
Beta-blockers
May reduce conversion of T4 to T3.
Proton pump inhibitors
May decrease levothyroxine absorption.
Antacids, iron, calcium supplements
Decrease levothyroxine absorption. Separate administration by at least 4 hours.
Estrogens (e.g., oral contraceptives)
May increase levothyroxine requirements.
Bile acid sequestrants (e.g., cholestyramine)
Decrease levothyroxine absorption. Separate by 4-6 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 may include fever, insomnia, tremors, palpitations, anxiety, sweating, weight loss, and diarrhea. Management involves symptomatic and supportive treatment. Beta-blockers may be used to control cardiovascular symptoms.
Pregnancy & Lactation
Pregnancy Category A. Levothyroxine is essential for fetal neurological development. Dosage requirements may increase during pregnancy. It is generally considered safe during lactation; small amounts are excreted in breast milk but are not known to adversely affect the infant.
Frequently Asked Questions
Common questions about this medicine
Pack Sizes
Shelf Life
Typically 2-3 years from manufacturing date.
Availability
Pharmacies, Hospitals
Approval Status
FDA Approved, DGDA Approved
Patent Status
Generic available (patent expired)
WHO Essential Medicine
YesClinical Trials
Levothyroxine has undergone extensive clinical trials demonstrating its efficacy and safety for treating hypothyroidism and related conditions, dating back decades. Ongoing research focuses on optimal dosing, interactions, and specific populations.
Lab Monitoring
- Serum TSH (Thyroid-Stimulating Hormone) levels: Primary test to monitor treatment efficacy; aims for TSH within normal range.
- Free T4 levels: May be monitored, especially in central hypothyroidism or TSH resistance.
- Periodic monitoring of thyroid function tests (TSH, Free T4) is crucial, usually every 4-8 weeks until stable, then every 6-12 months.
Doctor Notes
- Emphasize consistent administration (same time daily, empty stomach).
- Counsel patients on symptoms of both hypothyroidism and hyperthyroidism, and to report changes.
- Advise patients about potential drug and food interactions, especially with calcium, iron, and antacids.
Patient Guidelines
- Take your medicine exactly as prescribed by your doctor.
- Take it on an empty stomach, 30-60 minutes before breakfast.
- Do not stop taking this medicine without consulting your doctor.
- Inform your doctor about all other medications, supplements, and herbal products you are taking.
- Regular blood tests are necessary to monitor your thyroid hormone levels.
Missed Dose Advice
If a dose is missed, take it as soon as you remember, unless it is almost time for your next dose. In that case, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one.
Driving Precautions
Levothyroxine typically does not impair the ability to drive or operate machinery. However, if you experience side effects like dizziness or tremors, avoid driving until you feel well.
Lifestyle Advice
- Maintain a balanced diet and regular exercise as advised by your healthcare provider.
- Avoid foods that interfere with levothyroxine absorption (e.g., soy, high fiber) for several hours after taking the medicine.
- Manage stress to support overall well-being.
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