(lee voe thye rox' een)
P / L : Caution during pregnancy and lactation
||See TERMINOLOGY & ABBREVIATIONS ||
|WARNING||Thyroid hormones, including Levothyroxine Sodium Tablets, USP, either alone or with other therapeutic agents, should not be used for the treatment of obesity for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects.|
Levothyroxine sodium is used for the following indications:
Hypothyroidism - As replacement or supplemental therapy in congenital or acquired hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Specific indications include: primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism and subclinical hypothyroidism. Primary hypothyroidism may result from functional deficiency, primary atrophy, partial or total congenital absence of the thyroid gland, or from the effects of surgery, radiation, or drugs, with or without the presence of goiter.
Pituitary TSH Suppression - In the treatment or prevention of various types of euthyroid goiters, including thyroid nodules, subacute or chronic Iymphocytic thyroiditis (Hashimoto's thyroiditis), multinodular goiter, and, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.
|Dosage & Administration||
The goal of replacement therapy is to achieve and maintain a clinical and biochemical euthyroid state. The goal of suppressive therapy is to inhibit growth and/or function of abnormal thyroid tissue. The dose of Levothyroxine Sodium Tablets, USP that is adequate to achieve these goals depends on a variety of factors including the patient's age, body weight, cardiovascular status, concomitant medical conditions, including pregnancy, concomitant medications, and the specific nature of the condition being treated. Hence, the following recommendations serve only as dosing guidelines. Dosing must be individualized and adjustments made based on periodic assessment of the patient's clinical response and laboratory parameters.
Levothyroxine Sodium Tablets, USP should be taken in the morning on an empty stomach, at least one-half hour to one hour before any food is eaten. Levothyroxine Sodium Tablets, USP should be taken at least 4 hours apart from drugs that are known to interfere with its absorption.
Due to the long half-life of levothyroxine, the peak therapeutic effect at a given dose of levothyroxine sodium may not be attained for 4-6 weeks.
Caution should be exercised when administering Levothyroxine Sodium Tablets, USP to patients with underlying cardiovascular disease, to the elderly, and to those with concomitant adrenal insufficiency .
Specific Patient Populations:
Hypothyroidism in Adults and in Children in Whom Growth and Puberty are Complete.
Therapy may begin at full replacement doses in otherwise healthy individuals less than 50 years old and in those older than 50 years who have been recently treated for hyperthyroidism or who have been hypothyroid for only a short time (such as a few months). The average full replacement dose of levothyroxine sodium is approximately 1.7 mcg/kg/day (e.g., 100-125 mcg/day for a 70 kg adult). Older patients may require less than 1 mcg/kg/day. Levothyroxine sodium doses greater than 200 mcg/day are seldom required. An inadequate response to daily doses ≥ 300 mcg/day is rare and may indicate poor compliance, malabsorption, and/or drug interactions.
For most patients older than 50 years or for patients under 50 years of age with underlying cardiac disease, an initial starting dose of 25-50 mcg/day of levothyroxine sodium is recommended, with gradual increments in dose at 6-8 week intervals, as needed. The recommended starting dose of levothyroxine sodium in elderly patients with cardiac disease is 12.5-25 mcg/day, with gradual dose increments at 4-6 week intervals. The levothyroxine sodium dose is generally adjusted in 12.5-25 mcg increments until the patient with primary hypothyroidism is clinically euthyroid and the serum TSH has normalized.
In patients with severe hypothyroidism, the recommended initial levothyroxine sodium dose is 12.5-25 mcg/day with increases of 25 mcg/day every 2-4 weeks, accompanied by clinical and laboratory assessment, until the TSH level is normalized.
In patients with secondary (pituitary) or tertiary (hypothalamic) hypothyroidism, the levothyroxine sodium dose should be titrated until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range.
Pediatric Dosage - Congenital or Acquired Hypothyroidism
In general, levothyroxine therapy should be instituted at full replacement doses as soon as possible. Delays in diagnosis and institution of therapy may have deleterious effects on the child's ininformectual and physical growth and development.
Undertreatment and overtreatment should be avoided.
Levothyroxine Sodium Tablets, USP may be administered to infants and children who cannot swallow intact tablets by crushing the tablet and suspending the freshly crushed tablet in a small amount (5-10 mL or 1-2 teaspoons) of water. This suspension can be administered by spoon or dropper. DO NOT STORE THE SUSPENSION. Foods that decrease absorption of levothyroxine, such as soybean infant formula, should not be used for administering levothyroxine sodium tablets. (see PRECAUTIONS, Drug-Food Interactions).
The recommended starting dose of levothyroxine sodium in newborn infants is 10-15 mcg/kg/day. A lower starting dose (e.g., 25 mcg/day) should be considered in infants at risk for cardiac failure, and the dose should be increased in 4-6 weeks as needed based on clinical and laboratory response to treatment. In infants with very low (< 5 mcg/dL) or undetectable serum T4 concentrations, the recommended initial starting dose is 50 mcg/day of levothyroxine sodium.
Infants and Children
Levothyroxine therapy is usually initiated at full replacement doses, with the recommended dose per body weight decreasing with age (see TABLE 3). However, in children with chronic or severe hypothyroidism, an initial dose of 25 mcg/day of levothyroxine sodium is recommended with increments of 25 mcg every 2-4 weeks until the desired effect is achieved.
Hyperactivity in an older child can be minimized if the starting dose is one-fourth of the recommended full replacement dose, and the dose is then increased on a weekly basis by an amount equal to one-fourth the full-recommended replacement dose until the full recommended replacement dose is reached.
Table 3: Levothyroxine Sodium Dosing Guidelines for Pediatric Hypothyroidism
a. The dose should be adjusted based on clinical response and laboratory parameters
The signs and symptoms of overdosage are those of hyperthyroidism. In addition, confusion and disorientation may occur. Cerebral embolism, shock, coma, and death have been reported. Seizures have occurred in a child ingesting 18 mg of levothyroxine. Symptoms may not necessarily be evident or may not appear until several days after ingestion of levothyroxine sodium.
Treatment of Overdosage
Levothyroxine sodium should be reduced in dose or temporarily discontinued if signs or symptoms of overdosage occur.
Acute Massive Overdosage - This may be a life-threatening emergency, therefore, symptomatic and supportive therapy should be instituted immediately. If not contraindicated (e.g., by seizures, coma, or loss of the gag reflex), the stomach should be emptied by emesis or gastric lavage to decrease gastrointestinal absorption. Activated charcoal or cholestyramine may also be used to decrease absorption. Central and peripheral increased sympathetic activity may be treated by administering Î²-receptor antagonists, e.g., propranolol, provided there are no medical contraindications to their use. Provide respiratory support as needed; control congestive heart failure and arrhythmia; control fever, hypoglycemia, and fluid loss as necessary. Large doses of antithyroid drugs (e.g., methimazole or propylthiouracil) followed in one to two hours by large doses of iodine may be given to inhibit synthesis and release of thyroid hormones. Glucocorticoids may be given to inhibit the conversion of T4 to T3. Plasmapheresis, charcoal hemoperfusion and exchange transfusion have been reserved for cases in which continued clinical deterioration occurs despite conventional therapy. Because T4 is highly protein bound, very little drug will be removed by dialysis.
Levothyroxine is contraindicated in patients with untreated subclinical (suppressed serum TSH level with normal T3 and T4 levels) or overt thyrotoxicosis of any etiology and in patients with acute myocardial infarction. Levothyroxine is contraindicated in patients with uncorrected adrenal insufficiency since thyroid hormones may precipitate an acute adrenal crisis by increasing the metabolic clearance of glucocorticoids . Levothyroxine Sodium Tablets, USP is contraindicated in patients with hypersensitivity to any of the inactive ingredients in Levothyroxine Sodium Tablets, USP.
|Special Precautions||Angina, heart failure; DM; diabetes insipidus; elderly; long-standing hypothyroidism; adrenal insufficiency; myxoedema. Do not use for treatment of obesity or for wt loss. Pregnancy, lactation.|
|Adverse Drug Reaction(s)||Nervousness, excitability, tremor, muscle weakness, cramps; sweating, flushing, heat intolerance, headache, insomnia, tachycardia, palpitations, angina pectoris, excessive wt loss; menstrual irregularities; diarrhoea, vomiting.
Potentially Fatal: Convulsions, cardiac arrhythmia, heart failure, coma.
|Drug Interactions||Reduced absorption with iron, colestyramine, colestipol, aluminium- and magnesium-containing antacids, calcium carbonate, simethicone, sucralfate. May alter requirements of antidiabetic drugs. Reduced efficacy of thyroid replacement therapy with imatinib. Reduced tri-iodothyronine serum levels with amiodarone. Reduced serum levels of thyroxine with carbamazepine, phenytoin, phenobarbital, rifampicin, oestrogens.
Potentially Fatal: Increased therapeutic and toxic effects of levothyroxine and TCAs. May change hypoprothrombinaemic response to warfarin and other oral anticoagulants (markedly increased response during replacement). Increased risk of significant hypertension and tachycardia with ketamine.
|Food Interaction||Decreased bioavailability and lower serum levels of thyroxine with enteral nutrition. Reduced absorption with soybean infant formula, cottonseed meal, walnuts and dietary fibre.|
|Lab Interference||May alter thyroid function tests.|
|Pregnancy Category (FDA) and use in Specific Population||
Pregnancy - Category A
Studies in women taking levothyroxine sodium during pregnancy have not shown an increased risk of congenital abnormalities. Therefore, the possibility of fetal harm appears remote. Levothyroxine Sodium Tablets, USP should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated.
Hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, pre-eclampsia, stillbirth and premature delivery. Maternal hypothyroidism may have an adverse effect on fetal and childhood growth and development. During pregnancy, serum T4 levels may decrease and serum TSH levels increase to values outside the normal range. Since elevations in serum TSH may occur as early as 4 weeks gestation, pregnant women taking Levothyroxine Sodium Tablets, USP should have their TSH measured during each trimester. An elevated serum TSH level should be corrected by an increase in the dose of Levothyroxine Sodium Tablets, USP. Since postpartum TSH levels are similar to preconception values, the Levothyroxine Sodium Tablets, USP dosage should return to the pre-pregnancy dose immediately after delivery. A serum TSH level should be obtained 6-8 weeks postpartum.
Thyroid hormones cross the placental barrier to some extent as evidenced by levels in cord blood of athyroceotic fetuses being approximately one third maternal levels. Transfer of thyroid hormone from the mother to the fetus, however, may not be adequate to prevent in utero, hypothyroidism.
Although thyroid hormones are excreted only minimally in human milk, caution should be exercised when Levothyroxine Sodium Tablets, USP is administered to a nursing woman. However, adequate replacement doses of levothyroxine are generally needed to maintain normal lactation.
The goal of treatment in pediatric patients with hypothyroidism is to achieve and maintain normal ininformectual and physical growth and development.
The initial dose of levothyroxine varies with age and body weight (see Table 3). Dosing adjustments are based on an assessment of the individual patient's clinical and laboratory parameters.
In children in whom a diagnosis of permanent hypothyroidism has not been established, it is recommended that levothyroxine administration be discontinued for a 30-day trial period, but only after the child is at least 3 years of age. Serum T4 and TSH levels should then be obtained. If the T4 is low and the TSH high, the diagnosis of permanent hypothyroidism is established, and levothyroxine therapy should be reinstituted. If the T4 and TSH levels are normal, euthyroidism may be assumed and, therefore, the hypothyroidism can be considered to have been transient. In this instance, however, the physician should carefully monitor the child and repeat the thyroid function tests if any signs or symptoms of hypothyroidism develop. In this setting, the clinician should have a high index of suspicion of relapse. If the results of the levothyroxine withdrawal test are inconclusive, careful follow-up and subsequent testing will be necessary.
Since some more severely affected children may become clinically hypothyroid when treatment is discontinued for 30 days, an alternate approach is to reduce the replacement dose of levothyroxine by half during the 30-day trial period. If, after 30 days, the serum TSH is elevated above 20 mU/L, the diagnosis of permanent hypothyroidism is confirmed, and full replacement therapy should be resumed. However, if the serum TSH has not risen to greater than 20 mU/L, levothyroxine treatment should be discontinued for another 30-day trial period followed by repeat serum T4 and TSH.
The presence of concomitant medical conditions should be considered in certain clinical circumstances and, if present, appropriately treated .
Rapid restoration of normal serum T4 concentrations is essential for preventing the adverse effects of congenital hypothyroidism on ininformectual development as well as on overall physical growth and maturation. Therefore, Levothyroxine Sodium Tablets, USP therapy should be initiated immediately upon diagnosis and is generally continued for life.
During the first 2 weeks of Levothyroxine Sodium Tablets, USP therapy, infants should be closely monitored for cardiac overload, arrhythmias, and aspiration from avid suckling.
The patient should be monitored closely to avoid undertreatment or overtreatment. Undertreatment may have deleterious effects on ininformectual development and linear growth. Overtreatment has been associated with craniosynostosis in infants, and may adversely affect the tempo of brain maturation and accelerate the bone age with resultant premature closure of the epiphyses and compromised adult stature.
Acquired Hypothyroidism in Pediatric Patients
The patient should be monitored closely to avoid undertreatment and overtreatment. Undertreatment may result in poor school performance due to impaired concentration and slowed mentation and in reduced adult height. Overtreatment may accelerate the bone age and result in premature epiphyseal closure and compromised adult stature.
Treated children may manifest a period of catch-up growth, which may be adequate in some cases to normalize adult height. In children with severe or prolonged hypothyroidism, catch-up growth may not be adequate to normalize adult height.
Because of the increased prevalence of cardiovascular disease among the elderly, levothyroxine therapy should not be initiated at the full replacement dose.
|Storage||Store at 15-30°C (59-86°F).|
|Pharmacology||Levothyroxine sodium increases the basal metabolic rate (BMR) of carbohydrates, fats and proteins. It is also involved in the regulation and differentiation of cell growth. These effects are mediated at the cellular level by the thyroxine metabolite, tri-iodothyronine.
Onset: Oral: 3-5 days; IV: 6-8 hr.
Absorption: Variable but adequate from the GI tract (oral); increased in fasting state.
Distribution: Crosses the placenta; enters breast milk. Protein-binding: Extensive to thyroxine-binding globulin.
Metabolism: Hepatic and renal; converted to liothyronine and inactive reverse triiodothyronine; undergoes enterohepatic recirculation.
Excretion: Via faeces. Half-life: 6-7 days (euthyroid); prolonged in hypothyroidism and reduced in hyperthyroidism.
|ATC Classification||H03AA01 - levothyroxine sodium; Belongs to the class of thyroid hormones. Used in the management of thyroid diseases.|
|Brand Name||Manufacturer/Marketer||Composition||Dosage Form||Pack Size & Price|
|ELTROXIN||GlaxoSmithKline Bangladesh Limited||Levothyroxine sodium 50mcg||Tablet||100's: 255.60 MRP|
|Euthycin||Incepta Pharmaceuticals Limited||Levothyroxine Sodium 50 mcg Tablet||Tablet||10x10's:MRP 120 Tk|
|JAROXIN-50||Jayson Pharmaceuticals Ltd.||Levothyroxine sodium 50mcg||Tablet||100's: 120.00 IP|
|LEROXIN-50||Popular Pharmaceuticals Ltd.||Levothyroxine sodium 50mcg||Tablet||100's: 120.00 MRP|
|THYRIN||Square Pharmaceuticals Ltd.||Levothyroxine Sodium 50 mcg||Tablet||6x15's: 144.00 MRP|
|THYRIN 25||Square Pharmaceuticals Ltd.||Levothyroxine Sodium 25 mcg||Tablet||4x15's: 66.60 MRP|
|THYROLAR||The Acme Laboratories Ltd.||Thyroxine sodium 50mcg||Tablet||90's: 108.00 MRP|
|THYRONOR||Nuvista Pharma Limited||Thyroxine sodium 50mcg||Tablet||60's, 100's: 124.20 & 207.00 MRP|
|THYROX||Renata Limited||Thyroxine sodium 50mcg||Tablet||90's: 135.00 MRP|
Thyroid hormone should not be used to treat obesity in patients with normal thyroid function. Levothyroxine is ineffective for weight reduction in normal thyroid patients and may cause serious or life-threatening toxicity, especially when taken with amphetamines. Talk to your doctor about the potential risks associated with Levothyroxine.
Why is Levothyroxine prescribed?
Levothyroxine, a thyroid hormone, is used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. Without this hormone, the body cannot function properly, resulting in: poor growth; slow speech; lack of energy; weight gain; hair loss; dry, thick skin; and increased sensitivity to cold. When taken correctly, levothyroxine reverses these symptoms. Levothyroxine is also used to treat congenital hypothyroidism (cretinism) and goiter (enlarged thyroid gland).
Levothyroxine is sometimes prescribed for other uses; ask your doctor for more information.
How should Levothyroxine be used?
Levothyroxine comes as a tablet to take by mouth. It usually is taken once a day on an empty stomach, one half to one hour before breakfast. Follow the directions on your prescription label carefully, and ask your doctor to explain any part you do not understand. Take levothyroxine exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
The tablets may get stuck in your throat or cause choking or gagging; therefore, the tablet should be taken with a full glass of water.
If you are giving levothyroxine to an infant or child who cannot swallow the tablet, crush the tablet and mix it in 1 to 2 teaspoons of plain water. Give this mixture by spoon or dropper right away. Do not store this mixture. Only mix the crushed tablets with water. Do not mix with food or soybean infant formula.
Your doctor will probably start you on a low dose of levothyroxine and gradually increase your dose.
Levothyroxine controls hypothyroidism, but does not cure it. It may take several weeks before you notice a change in your symptoms. Continue to take levothyroxine even if you feel well. Do not stop taking levothyroxine without talking to your doctor.
What special precautions to follow?
Before taking levothyroxine,
- inform your doctor if you are allergic to levothyroxine, thyroid hormone, any other medications, or any of the ingredients in levothyroxine. Ask your pharmacist for a list of the ingredients.
- inform your doctor what prescription and nonprescription medications you are taking, especially amphetamines; anticoagulants ('blood thinners') such as warfarin; antidepressants or anti-anxiety agents; arthritis medicine; aspirin; beta-blockers such as metoprolol, propranolol or timolol; cancer chemotherapy agents; diabetes medications (insulin and tablets); digoxin; estrogens; methadone; oral contraceptives; phenytoin; steroids; theophylline and vitamins.
- if you take an antacid, calcium carbonate, cholestyramine , colestipol, iron, orlistat (Xenical), simethicone, sodium polystrene sulfonate, or sucralfate, take it at least 4 hours before or 4 hours after you take levothyroxine.
- inform your doctor if you have or have ever had diabetes; hardening of the arteries (atherosclerosis); kidney disease; hepatitis; cardiovascular disease such as high blood pressure, chest pain (angina), arrhythmias, or heart attack; or an underactive adrenal or pituitary gland.
- inform your doctor if you are pregnant, plan to become pregnant or are breast-feeding. If you become pregnant while taking levothyroxine, call your doctor.
- if you have surgery, including dental surgery, inform the doctor or dentist that you are taking levothyroxine.
What special dietary instructions to follow?
Unless your doctor informs you otherwise, continue your normal diet.
What to do if I forget a dose?
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
What side effects can Levothyroxine cause?
Levothyroxine may cause side effects. inform your doctor if any of these symptoms are severe or do not go away:
excessiv e sweating
changes in menstrual cycle
sensitivity to heat
- temporary hair loss, particularly in children during the first month of therapy
If you experience either of the following symptoms, call your doctor immediately or get emergency medical treatment:
chest pain (angina)
- rapid or irregular heartbeat or pulse
What to know about storage and disposal of Levothyroxine?
Keep Levothyroxine in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.
In case of emergency/overdose
In case of overdose, consult your doctor. If the victim has collapsed or is not breathing, consult local medical emergency services.
What other information to know?
Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to Levothyroxine.
Do not let anyone else use your medication. If you still have symptoms and need further treatment, consult your doctor.
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.
Ref: U.S. National Library of Medicine.
This information is provided for reference only and not a replacement for and should only be used in conjunction with full consultation with a registered medical practitioner. It may not contain all the available information you require and cannot substitute professional medical care, nor does it take into account all individual circumstances. Although great effort has been made to ensure content accuracy, mph-bd shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise.
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