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Levothyroxine Dosage

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Last Updated: 28 October 2020

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General | Latest Info

HYPOTHYROIDISM is a common medical condition which causes deficiency or low level of Thyroid hormone. PATIENTS WITH HYPOTHYROIDISM are treated by taking Thyroid hormone pills on a daily basis. The Majority of PATIENTS WITH HYPOTHYROIDISM take synthetic form of Thyroid hormone called Levothyroxine. The Levothyroxine structure is identical to T 4, main hormone secreted into blood by the Thyroid gland. The dose of Levothyroxine for any individual patient is different; best dose should be able to keep the level of Thyroid hormone tests within normal range and help to improve symptoms of HYPOTHYROIDISM. However, many PATIENTS WITH HYPOTHYROIDISM do not take the right dose and are either over-treat or undertreated. Over-treatment may cause irregular heart beats and bone loss in the elderly and under-treatment may cause symptoms like weight gain, fatigue as well as other serious health issues like higher cholesterol level, and in SEVERE cases, heart problems and even death. In this study, authors evaluated the effect of sex, age and body weight on blood level of Thyroid hormone in PATIENTS taking Levothyroxine. Younis IR et al 2018 Stable isotope pharmacokinetic studies provide insight into the effects of age, sex, and weight on Levothyroxine metabolism. Thyroid 28: 41-49. Epub 2018 Jan 2.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

What is levothyroxine?

Get emergency medical help if you have signs OF allergic reaction to levothyroxine: hives; difficult breathing; swelling OF your face, lips, tongue, or throat. Fast or irregular heartbeats; chest pain, pain spreading to your jaw or shoulder; shortness of breath; fever, hot flashes, sweating; tremors, or if you feel unusually cold; weakness, tiredness, sleep problems; memory problems, feeling depressed or irritable; headache, leg cramps, muscle aches; feeling nervous or irritable; dryness of your skin or hair, hair loss; irregular menstrual periods; or vomiting, diarrhea, appetite changes, weight changes. Certain side effects may be more likely in older adults. Chest pain, irregular heartbeats; shortness of breath; tremors, muscle pain or weakness; headache, leg cramps; feeling nervous or irritable, trouble sleeping; increased appetite; feeling hot; weight loss; changes in your menstrual periods; diarrhea; or skin rash, partial hair loss. This is not a complete list OF side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Warnings

Thyroid Hormones, either alone or with other therapeutic agents, should not be used for treatment of obesity or 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. This medication contains Levothyroxine. Do not take SYNTHROID, Levoxyl, L Thyroxine, Levo T, Levothroid, Levothyroxine T4, Levoxine, Tirosint, or Unithroid If you are allergic to Levothyroxine or any ingredients contained in this Drug. Keep out of reach of children. In case of overdose, get medical help or contact the Poison Control Center immediately.


Side Effects

Adverse reactions associated with SYNTHROID therapy are primarily those of hyperthyroidism due to therapeutic overdosage. They include the following: general: fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating Central nervous system: headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia Musculoskeletal: tremors, muscle weakness, muscle spasm Cardiovascular: palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest Respiratory: dyspnea Gastrointestinal: diarrhea, vomiting, abdominal cramps, elevations in liver function tests Dermatologic: hair loss, flushing, rash Endocrine: decrease bone mineral density Reproductive: menstrual irregularities, impaired fertility seizures have been report rarely with institution of levothyroxine therapy.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Take as directed

Levothyroxine is a medicine used to treat people with hypothyroidism. Hypothyroidism means people's Thyroid gland doesnt make enough Thyroid hormone. People with this condition may no longer have functioning Thyroid, or hypothyroidism can be caused by a variety of other reasons that affect Thyroid hormone production. Levothyroxine is also used to prevent or treat goiter or with other therapies to treat Thyroid cancer. This drug is a hormone, which works by replacing Thyroid hormone that your body normally produce. The US Food and Drug Administration initially approved this medicine in 1969. Its market under various brands.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Proper Use

In deciding to use medicine, risks of taking medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, following should be consider: tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully. Appropriate studies performed to date have not demonstrated pediatric-specific problems that would limit the usefulness of levothyroxine in children. Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of levothyroxine in the elderly. However, elderly patients are more likely to have age-related heart or blood vessel problems, which may require caution and adjustment in dose for patients receiving levothyroxine. Studies in women suggest that this medication poses minimal risk to infant when used during breastfeeding. Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines list below. Following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive. Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both medicines. Midodrine using this medicine with any of the following medicines may cause increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both medicines. Aluminum Carbonate, Basic Aluminum Hydroxide Aluminum Phosphate Calcium Acetate Calcium Carbonate Calcium Citrate Chlorotrianisene Cholestyramine Chromium Ciprofloxacin Colesevelam conjugate Estrogens conjugate Estrogens Synthetic conjugate Estrogens Synthetic B Dexlansoprazole Dienestrol Diethylstilbestrol Dihydroxyaluminum Aminoacetate Dihydroxyaluminum Sodium Carbonate Eltrombopag Esomeprazole esterify Estrogens Estradiol Estramustine Estriol Estropipate Ethinyl Estradiol Fosphenytoin Imatinib Iron Kelp Lansoprazole Lanthanum Carbonate Lopinavir Magaldrate Magnesium Carbonate Magnesium Hydroxide Magnesium Oxide Magnesium Trisilicate Mestranol Omeprazole Pantoprazole Patiromer Phenytoin Polyestradiol Phosphate Promestriene Quinestrol Rabeprazole Rifampin Ritonavir Semaglutide Sevelamer Simvastatin Tibolone certain medicines should not be use at or around time of eating food or eating certain types of food since interactions May occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

5. Side effects

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval. Some products that may interact with this drug include: blood thinners, digoxin, sucroferric oxyhydroxide. Many Drugs can exert effects on Thyroid hormone pharmacokinetics and Metabolism and May Alter therapeutic response to SYNTHROID. Table 3: Drugs that May Alter T4 and Triiodothyronine serum Transport Without Affecting Free Thyroxine concentration Table 4: Drugs that May Alter Hepatic Metabolism of T4 Table 5: Drugs that MayDecrease Conversion of T4 to T3 addition of SYNTHROID therapy in Patients with diabetes mellitus May worsen glycemic control and result in increase antidiabetic agent or insulin requirements. Carefully monitor glycemic control, especially when Thyroid therapy is start, change, or discontinue. SYNTHROID increases response to oral anticoagulant therapy. Therefore, decrease in dose of anticoagulant may be warranted with correction of hypothyroid state or when SYNTHROID dose is increase. Closely monitor coagulation tests to permit appropriate and timely dosage adjustments. SYNTHROID may reduce the therapeutic effects of digitalis glycosides. Serum digitalis glycoside levels may decrease when hypothyroid Patient become Euthyroid, necessitating an increase in dose of digitalis glycosides. Concurrent use of tricyclic or tetracyclic antidepressants and SYNTHROID may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. Toxic effects may include increased risk of cardiac arrhythmias and central nervous system stimulation. SYNTHROID may accelerate the onset of action of tricyclics. Administration of sertraline in Patients stabilize on SYNTHROID May result in increased SYNTHROID requirements. Concurrent use of ketamine and SYNTHROID may produce marked hypertension and tachycardia. Closely monitor blood pressure and heart rate in these patients. Concurrent use of sympathomimetics and SYNTHROID may increase the effects of sympathomimetics or Thyroid hormone. Thyroid Hormones may increase the risk of coronary insufficiency when sympathomimetic agents are administered to patients with coronary artery disease. Concurrent use of tyrosine-kinase inhibitors such as imatinib may cause hypothyroidism. Closely monitor TSH levels in such patients. Consumption of certain foods may affect SYNTHROID absorption, thereby necessitating adjustments in dosing. Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease absorption of SYNTHROID from the gastrointestinal tract. Grapefruit juice may delay absorption of levothyroxine and reduce its bioavailability. Consider changes in TBG concentration when interpreting T4 and T3 values. Measure and evaluate unbound hormones and / or determine the Free-T4 index in these circumstance. Pregnancy, infectious hepatitis, estrogens, estrogen-containing oral contraceptives, and acute intermittent porphyria increase TBG concentration. Nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, androgens, and corticosteroids decrease TBG concentration. Familial hyper-or hypo-Thyroxine binding globulinemias have been describe, with incidence of TBG deficiency approximating 1 in 9000.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

7. Cautions with other medicines

This medicine will need to be taken for the rest of your life of your child's life. Do not stop taking this medicine or change your doses without first checking with your doctor. It may take several weeks before you start to notice improvement in your symptoms. If you use medicine to treat high cholesterol, kayexalate, or sevelamer, take liothyronine at least 4 hours before you take any of these medicines. The dose of this medicine will be different for different patients. Follow your doctor's orders or directions on the label. The following information includes only average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so. The amount of medicine that you take depends on the strength of medicine. Also, number of doses you take each day, time allowed between doses, and length of time you take medicine depend on the medical problem for which you are using medicine. For oral dosage form: for hypothyroidism: AdultsAt first, 25 micrograms once a day. Your doctor may adjust your dose as needed However, dose is usually not more than 75 mcg per day. Older AdultsAt first, 5 mcg once a day. Your doctor may adjust your dose as needed ChildrenAt first, 5 mcg once a day. Your doctor may adjust your dose as needed For Thyroid cancer: Adults and ChildrenUse and dose must be determined by your doctor. For Thyroid problem diagnosis: Adults 75 to 100 micrograms once day for 7 days. Your doctor will give you radioactive iodine before and after 7-Day liothyronine. ChildrenUse's and dose must be determined by your doctor. If you miss dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip missing dose and go back to your regular dosing schedule. Do not double doses. Store medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing. Do not keep outdated medicine or medicine no longer need. Ask your healthcare professional how you should dispose of any medicine you do not use.


Interactions

Medicines that interact with levothyroxine may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with levothyroxine. Interaction between two medications does not always mean that you must stop taking one of medications. However, sometimes it does. Speak to your doctor about how drug interactions should be manage. Amiodarone or other medications that affect iodine, such as radioactive iodine amphetamines, such as dexamphetamine or phentermine anticoagulants, such as warfarin anticonvulsants such as carbamazepine, phenobarbital, or phenytoin antidepressants, such as sertraline or anti-anxiety medications aspirin ciprofloxacin estrogens and oral contraceptives heart medications, such as digoxin, metoprolol, or propranolol HIV medications medications for diabetes, including insulin medications that can affect absorption of levothyroxine, such as antacids, calcium carbonate, cholestyramine, iron, orlistat sucralfate, sevelamer, or proton pump inhibitors rifampin. Note that this list is not all-inclusive and includes only common medications that may interact with levothyroxine. You should refer to prescribing information for levothyroxine for a complete list of interactions.


Side Effects

You may wonder how often certain side effects occur with this drug. Heres some detail on several of the side effects this drug may cause. In some cases, Synthroid may cause weight loss. This is because thyroid hormones are responsible for your bodys metabolism. * If you dont have enough thyroid hormones in your body, your metabolism will be slower than usual. And this may lead to weight gain. However, if youre taking Synthroid, your thyroid hormone level should be within normal range. So with Synthroid treatment, your metabolism rate may increase, and you may lose weight. Its important to note that even though Synthroid may cause weight loss, Drug shouldnt be used specifically to aid in weight loss. In fact, Synthroid has boxed warning advising against using Drug for weight loss. A Boxed warning is the strongest warning required by the Food and Drug Administration. Boxed warnings alert doctors and patients about drug effects that may be dangerous. The Synthroids box warning states that it shouldnt be used to treat obesity or to help with weight loss. If your thyroid function is normal, Synthroid wo help you lose weight. In fact, using drugs at typical dosages in people without certain thyroid problems does lead to weight loss. And using doses larger than those recommended by manufacturer may cause serious side effects. These side effects can include confusion, seizures, coma, and even death. In addition, taking Synthroid along with drugs used for weight loss may cause very serious or even life - threatening side effects. If you have concerns or questions about weight loss while youre taking Synthroid, talk with your doctor. They can recommend ways to help you manage body weight. Thats healthy for you. There isnt any clinical study information that show how many people lose weight while taking Synthroid. However, small study looked at how many people lose weight while taking levothyroxine. This study shows that 52% of people taking levothyroxine lose weight after taking the drug for up to 24 months. And peoples average weight loss was 3. 8 kilograms. In some cases, Synthroids may lead to weight gain. This is because Drug can increase your appetite, which may make you eat more food than usual. It is also possible for you to gain weight if your dose of Synthroid isnt high enough for your body's needs. This is because if your thyroid hormone levels are high enough, your metabolism * may be slow. And this might make it easier for you to gain weight. But theres no information from clinical studies that show how many people have gained weight while taking Synthroid. If you have concerns about weight gain while youre taking Synthroid, talk with your doctor. They can recommend ways to help you manage body weight. Thats healthy for you. Hair loss is a rare side effect of Synthroid. But there are any clinical studies that show how many people have had hair loss while taking this drug.


Uses

Levothyroxine is used to treat underactive Thyroid. It replaces or provides more Thyroid hormone, which is normally produced by Thyroid gland. Low Thyroid hormone levels can occur naturally or when the Thyroid gland is injured by radiation / medications or removed by surgery. Having enough Thyroid hormone is important for maintaining normal mental and physical activity. In children, having enough Thyroid hormone is important for normal mental and physical development. This medication is also used to treat other types of Thyroid disorders. This medication should not be used to treat infertility unless it is caused by low Thyroid hormone levels.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

ADMINISTRATION

Table 1: LEVOXYL Dosing Guidelines for Pediatric Hypothyroidism

AgeDaily Dose Per Kg Body Weight
0 to 3 months10 mcg/kg daily to 15 mcg/kg daily
3 to 6 months8 mcg/kg daily to 10 mcg/kg daily
6 to 12 months6 mcg/kg daily to 8 mcg/kg daily
1 to 5 years5 mcg/kg daily to 6 mcg/kg daily
6 to 12 years4 mcg/kg daily to 5 mcg/kg daily
Greater than 12 years but growth and puberty incomplete2 mcg/kg daily to 3 mcg/kg daily
Growth and puberty complete1.6 mcg/kg daily

Administer on an empty stomach, at least 30 to 60 minutes before breakfast. Administer at least 4 hours apart from medications or food known to decrease absorption, and 4 hours apart from enteral feedings; evaluate need for dose adjustments when patient is regularly administering their dose within 1 hour of certain foods that may affect absorption. Soybean flour, cotton seed meal, walnuts, and dietary fiber decrease Levothyroxine absorption. Bioavailability is best when administered in a fasting state. May be administered intravenously or by intramuscular Injection. Intravenous route is prefer. Visually inspect parenteral products for particulate matter and discoloration before administration whenever solution and container permit. Reconstitution: Reconstitute by aseptically adding 5 mL of preservative-Free 0. 9% Sodium Chloride Injection, USP to vial of lyophilized Levothyroxine Sodium for Injection. Do not use other solutions to Reconstitute. Shake well to dissolve completely. The resultant solution will have final concentration as follow: approximately 20 mcg / mL for 100 mcg vial. Approximately 40 mcg / mL for 200 mcg vial. Approximately 100 mcg / mL for 500 mcg vial. The reconstituted injection is preservative free and is stable for 4 hours; unused portions should be discard. Levothyroxine oral solution may be administered in water or directly into the mouth. To administer in water, squeeze the contents of 1 single unit-dose ampule into a glass or cup containing water and stir. Do not dilute with any liquid other than water. Preparation should be administered immediately and consumed in its entirety to ensure all of the dose is receive. Rinse glass or cup with additional water and drink contents to ensure the entire dose is take. To administer directly, either squeeze it into your mouth or onto a spoon and immediately consume. Storage: Store unopened oral solution ampules in original container at 77 degrees F; excursions are permitted to 59 to 86 degrees F. Discard any unused ampules 15 days after opening pouch. Extemporaneous preparation of 25 mcg / mL Levothyroxine oral suspension: NOTE: Levothyroxine is not available as an FDA-approve oral suspension. With mortar and pestle, grind twenty-five 0. 1 mg Levothyroxine tablets into fine powder. In a separate container, measure 40 mL of glycerol. Add a small amount of glycerol to fine powder and mix into a uniform paste. Add geometric amounts of glycerol until the suspension is pourable. Transfer suspension to calibrated 100 mL amber bottle. In approximately 10 mL portions, rinse the mortar with remaining glycerol and transfer washings into amber bottle, trying to leave no Levothyroxine in the mortar. Add water to amber bottle to bring total volume to 100 mL. Label bottle appropriately, including'shake well before each use' and 'Refrigerate'. Suspension is stable for 8 days when stored at approximately 4 degrees C.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

CONTRAINDICATIONS / PRECAUTIONS

IF you will be taking this medicine for a long time, it is very important that your doctor check the progress of you or your child at regular visits. This will allow your doctor to see IF medicine is working properly and to decide IF you should continue to take it. Blood tests will be needed to check for unwanted effects. Levothyroxine should not be used for treatment of obesity or for the purpose of losing weight. This medicine is not effective for weight reduction. If taken in large amounts, Levothyroxine may cause serious unwanted effects. HYPOTHYROIDISM can sometimes cause infertility in men and women Levothyroxine should not be used for treatment of infertility unless it is caused by HYPOTHYROIDISM. For PATIENTS WITH diabetes: It is very important that you keep track of your blood or urine sugar levels as instructed by your doctor. Check WITH your doctor right away IF you notice any changes in your sugar levels. IF you think you have become PREGNANT while using this medicine, tell your doctor right away. You may need a larger dose of Levothyroxine while you are PREGNANT. WOMEN who are post-menopausal or who use this medicine for a long time may have some bone loss, which could lead to osteoporosis. Talk WITH your doctor IF you have questions or concerns about this. Call your doctor right away IF you or your child start to have rapid or irregular heartbeats, chest pain, leg cramps, headaches, nervousness, irritability, sleeplessness, tremors, change in appetite, weight gain or loss, vomiting, diarrhea, excessive sweating, heat intolerance, fever, changes in menstrual periods, hives, or skin rash. These could be symptoms of too much medicine in your body. Do not suddenly stop taking this medicine without first checking WITH your doctor. Your doctor may want you or your child to gradually reduce the amount you are using before stopping completely. Make sure any doctor or dentist who treats you knows that you or your child are using this medicine. You or your child may need to stop using this medicine several days before having surgery or medical tests. Temporary loss of hair may occur during the first few months of Levothyroxine therapy. Ask your doctor about this IF you have any concerns. Do not take other medicines unless they have been discussed WITH your doctor. This includes prescription or nonprescription - medicines and herbal or vitamin supplements.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

ADVERSE REACTIONS

Levothyroxine is administered orally or intravenously. Over 99% of levothyroxine is bind to proteins, primarily Thyroxine-binding globulin, prealbumin, and albumin. These proteins have a higher affinity for T4 than for liothyronine. Many medications and concurrent clinical conditions may affect T4 protein-binding, resulting in clinically significant changes in Thyroid hormone activity since Free drug is metabolically active. Thyroid Hormones do not readily cross the placental barrier, and only minimal amounts are distributed into breast milk. Levothyroxine exhibits slow metabolic clearance. The major pathway of Thyroid hormone Metabolism is through sequential deiodination. Approximately 80% of circulating T3 is derived from peripheral T4 by monodeiodination. Liver is a major site of degradation for both T4 and T3, WITH T4 deiodination also occurring at a number of additional sites, including kidney and other tissues. Approximately 80% of the daily dose of T4 is deiodinated to yield equal amounts of T3 and reverse T3. T3 and rT3 are further deiodinated to diiodothyronine. Thyroid Hormones are also metabolize via conjugation WITH glucuronides and sulfates and excrete directly into bile and gut where they undergo enterohepatic recirculation. Thyroid Hormones are primarily eliminated by the kidneys. Portion of conjugate hormone reach colon unchanged and is eliminated in feces. Approximately 20% of T4 is eliminated in feces. Urinary excretion of T4 decreases WITH age. Elimination half-life of levothyroxine is 6 to 7 days in Euthyroid PATIENTS, 9 to 10 days in hypothyroid PATIENTS, and 3 to 4 days in hyperthyroid PATIENTS. Elimination half-life of T3 is 2 days or less. Levothyroxine has a slower ONSET of action and longer duration than liothyronine. Full therapeutic effects of levothyroxine may not be evident for 1 to 3 weeks following oral administration and persist for the same amount of time following cessation of therapy. As hypothyroid patients become Euthyroid, TSH secretion decreases. Affect cytochrome P450 are and drug transporters: uridine 5'-diphospho-glucuronosyltransferase, and possibly intestinal P-glycoprotein induction of uridine 5'-diphospho-glucuronosyltransferase by other medications increase L-Thyroxine Hepatic Metabolism and lead to lower T4 serum levels. Literature has reported that levothyroxine might inhibit P-gp, and lower cyclosporine concentrations; However, this action of levothyroxine requires further study. Absorption of orally administering levothyroxine from the gastrointestinal tract ranges from 40% to 80%. Base on medical practice, relative bioavailability of oral levothyroxine is 48 to 74% that of injectable levothyroxine sodium. The majority of levothyroxine dose is absorbed from the jejunum and upper ileum. Relative bioavailability of oral tablets, compared to equal nominal dose of oral levothyroxine sodium solution, is approximately 93%. T4 absorption is increased by fasting, and decrease in malabsorption syndromes and by certain foods such as soybeans. Dietary fiber decreases bioavailability of T4. Absorption may also decrease WITH age. In addition, many drugs and foods affect T4 absorption. Certain foods, like soybean infant formula, enteral feedings, and dietary fiber, decrease T4 absorption. Consistent tablet potency was issued WITH oral levothyroxine products prior to 1984.


ADMINISTRATION

In patients with congenital hypothyroidism, assess the adequacy of replacement therapy by measuring both serum TSH and total or free-T4. Monitor TSH and total or free-T4 in children as follow: 2 and 4 weeks after initiation of treatment, 2 weeks after any change in dosage, and then every 3 to 12 months thereafter following dose stabilization until growth is complete. Poor compliance or abnormal values may necessitate more frequent monitoring. Perform routine clinical examination, including assessment of development, mental and physical growth, and bone maturation, at regular intervals. While the general aim of therapy is to normalize serum TSH level, TSH may not normalize in some patients due to in utero hypothyroidism causing resetting of pituitary-thyroid feedback. Failure of serum T4 to increase into the upper half of normal range within 2 weeks of initiation of SYNTHROID therapy and / or of serum TSH to decrease below 20 IU per liter within 4 weeks may indicate child is not receiving adequate therapy. Assess compliance, dose of medication administer, and method of administration prior to increasing the dose of SYNTHROID.


SIDE EFFECTS

Adverse reactions associated with levothyroxine therapy are primarily those of hyperthyroidism due to therapeutic overdosage. They include the following: General: fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating; central nervous system: Headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia; cardiac: Palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest; pseudotumor cerebri and slip capital femoral epiphysis have been report in children receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants and premature closure of epiphyses in children with resultant compromise adult height. Seizures have been reported rarely with institution of levothyroxine therapy. Inadequate levothyroxine dosage will produce or fail to ameliorate signs and symptoms of hypothyroidism. Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various GI symptoms, fever, arthralgia, Serum sickness and wheezing. Hypersensitivity to levothyroxine itself is not known to occur. In addition to the above events, following has been report, predominately when Levoxyl tablets were not take with water: choking, gagging, tablet stuck in throat and dysphagia. Read entire FDA prescribing INFORMATION for Levoxyl

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

MECHANISM OF ACTION

Levothyroxine is a synthetic version of the principle thyroid hormone, thyroxine that is made and released by the thyroid gland. Thyroid hormone increases the metabolic rate of cells of all tissues in the body. In fetus and newborn, thyroid hormones are important for growth and development of all tissues, including bones and the brain. In adults, thyroid hormones help to maintain brain function, utilization of food, and body temperature, among other effects. GENERIC AVAILABLE: Yes. GENERIC and branded tablets of levothyroxine may differ: in amount of levothyroxine they contain, absorption of levothyroxine into the body, and distribution of levothyroxine throughout the body. This means that ingestion of 1 mg of GENERIC levothyroxine may not have the same effect on the body as 1 mg of another GENERIC or branded levothyroxine. Practically speaking, this means that when changing between levothyroxine manufactured by different pharmaceutical companies, change in dose may be necessary to maintain the desired effect or to prevent toxicity. When switching between brands or generics, it is important to ensure that both preparations are equivalent or to check blood thyroid levels weekly. For adult HYPOTHYROIDISM, levothyroxine starts at 12. 5-125 mcg / day administer orally. Starting doses and dose changes may differ WITH individual PATIENTS based upon age, presence of cardiovascular DISEASE, development of tolerance, side effects of medication, and blood levels of thyroid hormone. It may take one to three weeks after initiating therapy WITH levothyroxine or changing dose before effects are see. The goal of replacement therapy is to maintain normal blood thyroxine level. Initiation or discontinuation of therapy WITH levothyroxine in diabetic PATIENTS may create the need for an increase or decrease in the required dose of insulin and / or antidiabetic drug,. Levothyroxine may increase the effect of blood thinners such as warfarin. Therefore, monitoring of blood clotting is necessary, and decrease in dose of warfarin May be necessary. Intravenous administration of epinephrine to PATIENTS WITH coronary artery DISEASE may lead to complications ranging from difficulty in breathing to heart attack. These complications may occur more frequently among PATIENTS also taking levothyroxine. Therefore, careful observation is needed when intravenous epinephrine is given to PATIENTS receiving levothyroxine who also have coronary artery DISEASE. Converting state of HYPOTHYROIDISM to normal state WITH levothyroxine May decrease actions of certain beta-blocking drugs,. It may be necessary, therefore, to change the dose of beta-blocker. For the same reason, dose of digoxin, drug used to manage heart failure or irregular heart rhythm, also may need to be change. Converting HYPOTHYROIDISM to an euthyroid state WITH levothyroxine may increase the blood level of theophylline, and it may be necessary to change the dose of theophylline. Taking levothyroxine at the same time as calcium carbonate, ferrous sulfate, cholestyramine or colestipol may decrease the effect of levothyroxine and lead to HYPOTHYROIDISM. This occurs because levothyroxine binds to these drugs and is not absorb.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Dosing Considerations

Avoid under-treatment or over-treatment with this drug. This may result in adverse effects. Initiate lower dose of medicine in the elderly, those with angina pectoris, cardiovascular disease, or in those with severe hypothyroidism. Long-term therapy decreases bone mineral density; use lowest dose in postmenopausal women and women using suppressive doses. Lower dose of Tirosint capsules may be required compared with standard T4 tablets for hypothyroidism in patients with impaired gastric acid secretion to reach their target TSH levels; Tirosint has shown improved absorption compared with conventional T4 tablets. Check for bioequivalence if switching brands / generics, or every week after switching from one levothyroxine sodium preparation to another.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

What happens if I miss a dose?

0 to 3 months: 10 to 15 mcg / kg orally once day 3 to 6 months: 8 to 10 mcg / kg orally once day 6 to 12 months: 6 to 8 mcg / kg orally once day 1 to 5 years: 5 to 6 mcg / kg orally once day 6 to 12 years: 4 to 5 mcg / kg orally once day 12 years or older and incomplete growth and puberty: 2 to 3 mcg / kg orally once day 12 years or older with growth and puberty complete: 1. 6 mcg / kg orally per day Newborns at Risk For Cardiac Failure: Consider lower INITIAL DOSE; increase DOSE every 4 to 6 weeks As need based on clinical and laboratory response Pediatric Patients at Risk For Hyperactivity: INITIAL DOSE should be one-fourth recommended Full replacement DOSE; increase weekly by one-fourth to Full recommended replacement DOSE Comments:-DOSE should be individualize with regular monitoring of clinical status and laboratory parameters; peak effect may not be attain For 4 to 6 weeks.-Not indicate For treatment of Hypothyroidism during recovery phase of subacute thyroiditis.-Co-administer food and concomitant medications may significantly affect absorption; take on empty stomach and at least 4 hours before or after drugs know to interfere with levothyroxine absorption.-Capsule formulation is indicate For Patients 6 years or older As capsule should be swallow whole; see Other Comment / Administration Advice For specific Administration instructions including instructions For those unable to swallow intact tablets. Use: For treatment of congenital or acquire Hypothyroidism.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Thyroid Hormone Replacement

Most otherwise healthy adult patients with hypothyroidism require thyroid hormone replacement in dosage of 1. 7 g per kg per day, with requirements falling to 1 g per kg per day for the elderly. Thus, levothyroxine in dosage of 0. 10 to 0. 15 mg per day is needed to achieve euthyroid status. For full replacement, children may require up to 4 g per kg per day. 9 in young patients without risk factors for cardiovascular disease, thyroid hormone replacement can start close to target goal. In most healthy young adults, replacement is initiated using levothyroxine in dosage of 0. 075 mg per day, with dosage increasing slowly as indicated by continued elevation of TSH level. Levothyroxine should be initiated in low dosage in older patients and those at risk for cardiovascular compromise that could occur with rapid increase in resting heart rate and blood pressure. 9 in these patients, usual starting dosage is 0. 025 mg per day. This dosage can be increased in increments of 0. 025 to 0. 050 mg every four to six weeks until TSH level returns to normal. Thyroid hormone is usually given once daily, but some evidence suggests that weekly dosing may also be effective. In a small study, 10 of 12 patients with hypothyroidism, bolus dose of thyroid hormone equal to seven times the usual daily dose was well tolerate. Before weekly replacement can be recommend, however, more investigation is require, including definitions of populations in which this approach is indicate. In study 11 of 33 middle-age patients with stable hypothyroidism who were already receiving levothyroxine, small improvements in mood, memory and cold tolerance occurred after triiodothyronine was add, at dosage of 0. 0125 mg per day, with concomitant 0. 05-mg decrease in usual levothyroxine dosage. Although this study was small, it suggests that some patients who are chemically euthyroid but have lingering neuropsychiatric problems might benefit from triiodothyronine. Further investigation is required to determine the role of triiodothyronine in these patients, as well as the long-term consequences of its use.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Sources

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

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