Levothyroxine Sodium/Thyroxine Sodium
Thyroid Therapy · Thyroid hormone
Indications
Replacemental or supplemental therapy in hypothyroidism; pituitary TSH suppression.
Dosage
Adults: Initially 50-100 mcg increasing by 50 mcg at 3-4 wk intervals until normal metabolism is steadily maintained. Elderly: > 50 yr: Do not exceed 50 mcg/day initially. Cardiac diseases: 25 mcg daily or 50 mcg on alternate days, increase at 4 wk intervals. Congenital hypothyroidism and juvenile myxoedema: Initially 25 mcg daily increasing by 25 mcg every 2-4 wk; reduce slightly once mild toxic symptoms appear. Children: Hypothyroidism: Neonate, initially 10-15 mcg/kg once daily, max 50 mcg/day, adjusted in steps of 5 mcg/kg every 2 wk or as necessary; usual maintenance dose 20-50 mcg daily; 1 mth-2 yr, initially 5 mcg/kg once daily, max 50 mcg/day adjusted in steps of 10-25 mcg/day every 2-4 wk until metabolism normalised; usual maintenance dose 25-75 mcg/day; 2-12 yr, initially 50 mcg once daily adjusted in steps of 25 mcg/day every 2-4 wk until metabolism normalised; usual…
Adverse Effects
Anginal pain, cardiac arrhythmias, palpitation, skeletal muscles cramps, tachycardia, diarrhoea, vomiting, tremor, excitability, insomnia, headaches, flushing, weight loss, muscular weakness, sweating, rash, pruritus, oedema, restlessness, menstrual disorders, pseudotumour cerebri, heat intolerance. Transient alopecia in children.
Risk Factor (Pregnancy/Lactation)
Pregnancy: Controlled studies shown no risk. Lactation: May be used in breast feeding. Contraindications: Thyrotoxicosis. Precautions: Elderly. Cardiovascular disorders, diabetes. Longstanding hypothyroidism, adrenal insufficiency.
Interactions
Anticoagulants, cholestyramine, phenytoin, digitalis, insulin, antidiabetic therapy, amiodarone, rifampicin, anticonvulsants, TCADs, sertraline, lithium, sucralfate, polystyrene, sulfonate, sevelamer, cimetidine, antacids, oral iron, digoxin, sympathomimetics, NSAIDs, Beta blockers, oestrogen, androgens, corticosteroids, protease inhibitors, tyrosine kinase inhibitors, iodine-containing contrast media, soy suppl.
Advice to Patient
Take atleast 30 minutes before meals. Best to take before breakfast because it causes insomnia. Swallow tablet with a full glass of water. Contact prescriber if there is rash, hives, palpitations, chest pain, rapid heartbeat, change in menstrual pattern, change in appetite, vomiting, fever, intolerance to heat, agitation, irritability, increased nervousness, increased sweating, lethargy, diarrhoea, weight loss, leg cramps, headache. If you increase or decrease intake of food that causes goitre (such as peas, asparagus, cabbage, broccoli, spinach, turnip greens, lettuce, brussels sprouts, soybeans) consult prescriber. If pregnancy occurs, inform prescriber because dosage may need to be increased. Medication is given for lifetime. Avoid taking iron preparations, calcium supplements or antacids within 8 hours of taking this medication. Transient hair loss may occur during first few months…
Pharmacokinetics
Onset of action: Oral: 3-5 days. IV: Within 6-8 hrs. Absorption: Oral: Erratic; may be reduced by age and specific foods and drugs. Metabolism: Hepatic to triiodothyronine (T3; active); approx. 80% thyroxine (T4) deiodinated in kidney and periphery. Bioavailability: Oral tab: 64% (non-fasting state) to 79% to 81% (fasting state). Time to peak, serum: 2-4 hrs. Half-life elimination: Euthyroid: 6-8 days. Hypothyroid: 9-10 days. Hyperthyroid: 3-4 days. Excretion: Urine (major route). Faeces (approx. 20%).
Brands with this active ingredient
Compiled by Healify Pharmacy from published drug references. How we compile it →
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