Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Levothyroxine Basics
Document related concepts
Transcript
Levothyroxine Basics Images Formulation Details Description Synthroid® [Abbott Laboratories] (200 mcg) Synthroid® [Abbott Laboratories] (137 mcg) Formulation Details Synthroid® [Abbott Laboratories] (25 mcg) Formulation Details Synthroid® [Abbott Laboratories] (50 mcg) Formulation Details Synthroid® [Abbott Laboratories] (75 mcg) Formulation Details Synthroid® [Abbott Laboratories] (88 mcg) Formulation Details Synthroid® [Abbott Laboratories] (100 mcg) Formulation Details Images Description Synthroid® [Abbott Laboratories] (125 mcg) Formulation Details Synthroid® [Abbott Laboratories] (150 mcg) Formulation Details Synthroid® [Abbott Laboratories] (175 mcg) Formulation Details Synthroid® [Abbott Laboratories] (200 mcg) Formulation Details Synthroid® [Abbott Laboratories] (300 mcg) Formulation Details Synthroid® [Abbott Laboratories] (112 mcg) Formulation Details [Mylan Pharmaceuticals Inc] (25 mcg) Formulation Details Images Description [Mylan Pharmaceuticals Inc] (50 mcg) Formulation Details [Mylan Pharmaceuticals Inc] (75 mcg) Formulation Details [Mylan Pharmaceuticals Inc] (88 mcg) Formulation Details [Mylan Pharmaceuticals Inc] (100 mcg) Formulation Details [Mylan Pharmaceuticals Inc] (112 mcg) Formulation Details [Mylan Pharmaceuticals Inc] (125 mcg) Formulation Details [Mylan Pharmaceuticals Inc] (150 mcg) Formulation Details Images Description [Mylan Pharmaceuticals Inc] (175 mcg) Formulation Details [Mylan Pharmaceuticals Inc] (200 mcg) Formulation Details Formulation Details [Mylan Pharmaceuticals Inc] (300 mcg) Formulation Details [Mylan Pharmaceuticals Inc] (137 mcg) Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (50 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (100 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (125 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (150 mcg) Formulation Details Images Description Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (200 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (300 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (25 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (50 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (75 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (100 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (125 mcg) Formulation Details Images Description Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (150 mcg) Formulation Details Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (175 mcg) Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (200 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (300 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (88 mcg) Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (112 mcg) Formulation Details Formulation Details Levothroid® [Forest Pharmaceuticals Inc Sub Forest Labs Inc] (137 mcg) [Lannett Co Inc] (25 mcg) Formulation Details Images Description [Lannett Co Inc] (50 mcg) Formulation Details [Lannett Co Inc] (75 mcg) Formulation Details [Lannett Co Inc] (88 mcg) Formulation Details Formulation Details [Lannett Co Inc] (100 mcg) Formulation Details [Lannett Co Inc] (112 mcg) [Lannett Co Inc] (125 mcg) Formulation Details Formulation Details [Lannett Co Inc] (150 mcg) Formulation Details [Lannett Co Inc] (175 mcg) Formulation Details [Lannett Co Inc] (200 mcg) Formulation Details [Lannett Co Inc] (300 mcg) Unithroid® [Lannett Co Inc] (25 mcg) Formulation Details Images Description Unithroid® [Lannett Co Inc] (50 mcg) Formulation Details Unithroid® [Lannett Co Inc] (75 mcg) Formulation Details Unithroid® [Lannett Co Inc] (88 mcg) Formulation Details Formulation Details Unithroid® [Lannett Co Inc] (100 mcg) Formulation Details Unithroid® [Lannett Co Inc] (112 mcg) Unithroid® [Lannett Co Inc] (125 mcg) Formulation Details Formulation Details Unithroid® [Lannett Co Inc] (150 mcg) Formulation Details Unithroid® [Lannett Co Inc] (175 mcg) Formulation Details Unithroid® [Lannett Co Inc] (200 mcg) Formulation Details Unithroid® [Lannett Co Inc] (300 mcg) Formulation Details [Lannett Co Inc] (137 mcg) Formulation Details [Sandoz Inc] (25 mcg) Formulation Details [Sandoz Inc] (50 mcg) Images Description [Sandoz Inc] (75 mcg) Formulation Details [Sandoz Inc] (88 mcg) Formulation Details Formulation Details [Sandoz Inc] (100 mcg) [Sandoz Inc] (112 mcg) Formulation Details [Sandoz Inc] (125 mcg) Formulation Details [Sandoz Inc] (150 mcg) Formulation Details [Sandoz Inc] (175 mcg) Formulation Details [Sandoz Inc] (200 mcg) Images Description Formulation Details [Sandoz Inc] (300 mcg) Formulation Details [Sandoz Inc] (137 mcg) Formulation Details [UDL Laboratories Inc] (50 mcg) Formulation Details [UDL Laboratories Inc] (75 mcg) Formulation Details [UDL Laboratories Inc] (100 mcg) Formulation Details [UDL Laboratories Inc] (125 mcg) Formulation Details [UDL Laboratories Inc] (25 mcg) Images Description Formulation Details [UDL Laboratories Inc] (150 mcg) Formulation Details Levoxyl® [Jones Pharma Inc] (25 mcg) Formulation Details Levoxyl® [Jones Pharma Inc] (50 mcg) Formulation Details Levoxyl® [Jones Pharma Inc] (75 mcg) Formulation Details Levoxyl® [Jones Pharma Inc] (88 mcg) Formulation Details Levoxyl® [Jones Pharma Inc] (100 mcg) Formulation Details Levoxyl® [Jones Pharma Inc] (112 mcg) Images Description Formulation Details Levoxyl® [Jones Pharma Inc] (125 mcg) Formulation Details Levoxyl® [Jones Pharma Inc] (137 mcg) Formulation Details Levoxyl® [Jones Pharma Inc] (150 mcg) Formulation Details Levoxyl® [Jones Pharma Inc] (175 mcg) Formulation Details Levoxyl® [Jones Pharma Inc] (200 mcg) Formulation Details Formulation Details Levoxyl® [Jones Pharma Inc] (300 mcg) Formulation Details [Bedford Laboratories] (200 mcg) Formulation Details [Bedford Laboratories] (500 mcg) Levoxyl® [King Pharmaceuticals Inc] (25 mcg) Images Description Formulation Details Levoxyl® [King Pharmaceuticals Inc] (50 mcg) Formulation Details Levoxyl® [King Pharmaceuticals Inc] (75 mcg) Formulation Details Levoxyl® [King Pharmaceuticals Inc] (88 mcg) Formulation Details Levoxyl® [King Pharmaceuticals Inc] (100 mcg) Formulation Details Levoxyl® [King Pharmaceuticals Inc] (112 mcg) Formulation Details Levoxyl® [King Pharmaceuticals Inc] (125 mcg) Formulation Details Levoxyl® [King Pharmaceuticals Inc] (137 mcg) Images Description Formulation Details Levoxyl® [King Pharmaceuticals Inc] (150 mcg) Formulation Details Levoxyl® [King Pharmaceuticals Inc] (175 mcg) Formulation Details Levoxyl® [King Pharmaceuticals Inc] (200 mcg) Formulation Details Formulation Details [APP Pharmaceutical] (200 mcg) Formulation Details [APP Pharmaceutical] (500 mcg) Formulation Details Levo-T® [Zoetica Pharmaceutical Corp] (25 mcg) Formulation Details Levo-T® [Zoetica Pharmaceutical Corp] (75 mcg) Formulation Details Levo-T® [Zoetica Pharmaceutical Corp] (100 mcg) Formulation Details Levo-T® [Zoetica Pharmaceutical Corp] (125 mcg) Formulation Details Levo-T® [Zoetica Pharmaceutical Corp] (175 mcg) Formulation Details Levo-T® [Zoetica Pharmaceutical Corp] (300 mcg) Formulation Details Levo-T® [Zoetica Pharmaceutical Corp] (50 mcg) Formulation Details Levo-T® [Zoetica Pharmaceutical Corp] (88 mcg) Formulation Levo-T® [Zoetica Pharmaceutical Corp] (112 mcg) Images Description Details Formulation Details Levo-T® [Zoetica Pharmaceutical Corp] (150 mcg) Formulation Details Levo-T® [Zoetica Pharmaceutical Corp] (200 mcg) Formulation Details Levo-T® [Zoetica Pharmaceutical Corp] (137 mcg) U.S. Brand Names Levothroid®; Levoxyl®; Synthroid®; Unithroid® Medication Safety Issues Sound-alike/look-alike issues: Levothyroxine may be confused with lamoTRIgine, Lanoxin®, levofloxacin, liothyronine Levoxyl® may be confused with Lanoxin®, Levaquin®, Luvox® Synthroid® may be confused with Symmetrel® To avoid errors due to misinterpretation of a decimal point, always express dosage in mcg (not mg). Significant differences exist between oral and I.V. dosing. Use caution when converting from one route of administration to another. Generic Available Yes Pharmacologic Category Thyroid Product Related Terms L-Thyroxine Sodium; Levothyroxine Sodium; T4 Clinical Pharmacology Mechanism of Action Levothyroxine (T4) is a synthetic form of thyroxine, an endogenous hormone secreted by the thyroid gland. T4 is converted to its active metabolite, L-triiodothyronine (T3). Thyroid hormones (T4 and T3) then bind to thyroid receptor proteins in the cell nucleus and exert metabolic effects through control of DNA transcription and protein synthesis; involved in normal metabolism, growth, and development; promotes gluconeogenesis, increases utilization and mobilization of glycogen stores, and stimulates protein synthesis, increases basal metabolic rate Pharmacokinetics Onset of action: Therapeutic: Oral: 3-5 days; I.V. 6-8 hours Peak effect: I.V.: 24 hours Absorption: Oral: Erratic (40% to 80%); may be decreased by age and specific foods and drugs Protein binding: >99% bound to plasma proteins including thyroxine-binding globulin, thyroxine-binding prealbumin, and albumin Metabolism: Hepatic to triiodothyronine (active); T4 deiodination in kidney and periphery; glucuronidation/conjugation also occurs; undergoes enterohepatic recirculation Time to peak, serum: 2-4 hours Half-life elimination: Euthyroid: 6-7 days; Hypothyroid: 9-10 days; Hyperthyroid: 3-4 days Excretion: Urine (major route of elimination; decreases with age); feces (~20%) Indications & Usage Use Replacement or supplemental therapy in hypothyroidism; pituitary TSH suppression Use: Unlabeled/Investigational Management of hemodynamically unstable potential organ donors increasing the quantity of organs available for transplantation Contraindications Hypersensitivity to levothyroxine sodium or any component of the formulation; acute MI; thyrotoxicosis of any etiology; uncorrected adrenal insufficiency Warnings/Precautions Boxed warnings: • Weight reduction: See “Other warnings/precautions” below. Disease-related concerns: • Adrenal insufficiency: Use with caution in patients with adrenal insufficiency; symptoms may be exaggerated or aggravated. • Benign thyroid nodules: Appropriate use: Routine use of T4 for TSH suppression is not recommended in patients with benign thyroid nodules. Treatment should never be fully suppressive (TSH <0.1 mIU/mL) (Gharib, 2006; Cooper, 2006). - Use of T4 is often physician-dependent and may be considered in select patients, including patients who reside in iodine-deficient areas, young patients with small thyroid nodules, and patients with nonfunctioning nodular goiters (Gharib, 2006). - Use should be avoided in postmenopausal women, men >60 years of age, patients with cardiovascular disease, osteoporosis, or systemic illness, and patients with large thyroid nodules or long-standing goiters with a TSH level <1 mIU/mL (Gharib, 2006). • Cardiovascular disease: Use with caution and reduce dosage in patients with angina pectoris or other cardiovascular disease; chronic hypothyroidism predisposes patients to coronary artery disease. • Diabetes: Use with caution in patients with diabetes mellitus and insipidus; symptoms may be exaggerated or aggravated. • Myxedema: Use with caution in patients with myxedema; symptoms may be exaggerated or aggravated. • Osteoporosis: Long-term therapy can decrease bone mineral density. Postmenopausal women and women using suppressive doses should receive the lowest dose necessary for clinical response. Special populations: • Elderly: Use with caution; decrease initial dose; suppressed TSH levels may increase risk of atrial fibrillation and mortality secondary to cardiovascular disease. (Gharib, 2006). Dosage form specific issues: • Levoxyl®: Product may rapidly swell and disintegrate causing choking or gagging (should be administered with a full glass of water); use caution in patients with dysphagia or other swallowing disorders. Other warnings/precautions: • Weight reduction: [U.S. Boxed Warning]: Thyroid supplements are ineffective and potentially toxic when used for the treatment of obesity or for weight reduction, especially in euthyroid patients. High doses may produce serious or even life-threatening toxic effects particularly when used with some anorectic drugs (eg, sympathomimetic amines). Pregnancy & Lactation Pregnancy Risk Factor A Pregnancy Implications Untreated maternal hypothyroidism may have adverse effects on fetal growth and development and is associated with higher rate of complications (spontaneous abortion, pre-eclampsia, stillbirth, premature delivery). Treatment should not be discontinued during pregnancy. TSH levels should be monitored during each trimester and 6-8 weeks postpartum. Increased doses may be needed during pregnancy. Lactation Enters breast milk/compatible Adverse Reactions Frequency not defined. Cardiovascular: Angina, arrhythmia, cardiac arrest, flushing, heart failure, hypertension, MI, palpitation, pulse increased, tachycardia Central nervous system: Anxiety, emotional lability, fatigue, fever, headache, hyperactivity, insomnia, irritability, nervousness, pseudotumor cerebri (children), seizure (rare) Dermatologic: Alopecia Endocrine & metabolic: Fertility impaired, menstrual irregularities Gastrointestinal: Abdominal cramps, appetite increased, diarrhea, vomiting, weight loss Hepatic: Liver function tests increased Neuromuscular & skeletal: Bone mineral density decreased, muscle weakness, tremor, slipped capital femoral epiphysis (children) Respiratory: Dyspnea Miscellaneous: Diaphoresis, heat intolerance, hypersensitivity (to inactive ingredients, symptoms include urticaria, pruritus, rash, flushing, angioedema, GI symptoms, fever, arthralgia, serum sickness, wheezing) Levoxyl®: Choking, dysphagia, gagging Interactions Drug Interactions Bile Acid Sequestrants: May decrease the absorption of Thyroid Products. Risk C: Monitor therapy Calcium Polystyrene Sulfonate: May decrease the serum concentration of Thyroid Products. Management: To minimize risk of interaction, separate dosing of oral calcium polystyrene sulfonate and thyroid products (eg, levothyroxine) or administer calcium polystyrene sulfonate rectally. Monitor for signs/symptoms of hypothyroidism with concomitant use (oral). Risk D: Consider therapy modification Calcium Salts: May diminish the therapeutic effect of Thyroid Products. Management: Separate the doses of the thyroid product and the oral calcium supplement by at least 4 hours. Risk D: Consider therapy modification CarBAMazepine: May decrease the serum concentration of Thyroid Products. Risk C: Monitor therapy Estrogen Derivatives: May diminish the therapeutic effect of Thyroid Products. Risk C: Monitor therapy Iron Salts: May decrease the serum concentration of Levothyroxine. Management: Separate oral administration of iron salts and levothyroxine by at least 4 hours. Separation of doses is not required with parenterally administered iron salts or levothyroxine. Exceptions: Ferumoxytol; Iron Dextran Complex; Iron Sucrose. Risk D: Consider therapy modification Orlistat: May decrease the serum concentration of Levothyroxine. Management: Separate administration of oral levothyroxine and orlistat by a least 4 hours. Monitor patients closely for signs and symptoms of hypothyroidism. Risk D: Consider therapy modification Phenytoin: May increase the metabolism of Thyroid Products. Phenytoin may also displace thyroid hormones from protein binding sites. Risk C: Monitor therapy Raloxifene: May decrease the absorption of Levothyroxine. Risk D: Consider therapy modification Rifampin: May decrease the serum concentration of Thyroid Products. Risk C: Monitor therapy Sevelamer: May decrease the serum concentration of Levothyroxine. Management: Consider separating administration of sevelamer and levothyroxine by at least several hours whenever possible in order to decrease the risk of a significant interaction. Risk D: Consider therapy modification Sodium Iodide I131: Thyroid Products may diminish the therapeutic effect of Sodium Iodide I131. Risk X: Avoid combination Sodium Polystyrene Sulfonate: May decrease the serum concentration of Thyroid Products. Management: To minimize risk of interaction, separate dosing of oral sodium polystyrene sulfonate and thyroid products (e.g., levothyroxine) or administer sodium polystyrene sulfonate rectally. Monitor for signs/symptoms of hypothyroidism with concomitant use (oral). Risk D: Consider therapy modification Sucralfate: May decrease the serum concentration of Levothyroxine. Risk C: Monitor therapy Theophylline Derivatives: Thyroid Products may increase the metabolism of Theophylline Derivatives. Exceptions: Dyphylline. Risk C: Monitor therapy Vitamin K Antagonists (eg, warfarin): Thyroid Products may enhance the anticoagulant effect of Vitamin K Antagonists. Risk D: Consider therapy modification Ethanol/Nutrition/Herb Interactions Food: Taking levothyroxine with enteral nutrition may cause reduced bioavailability and may lower serum thyroxine levels leading to signs or symptoms of hypothyroidism. Soybean flour (infant formula), cottonseed meal, walnuts, and dietary fiber may decrease absorption of levothyroxine from the GI tract. Lab Test Interactions Many drugs may have effects on thyroid function tests (see Additional Information or Pharmacotherapy Pearls). Pregnancy, infectious hepatitis, and acute intermittent porphyria may increase TBG concentrations; nephrosis, severe hypoproteinemia, severe liver disease, and acromegaly may decrease TBG concentrations. Dosing Dosing: Adults Doses should be adjusted based on clinical response and laboratory parameters. Hypothyroidism: Adults, healthy adults <50 years of age, children in whom growth and puberty are complete, and older adults who have been recently treated for hyperthyroidism or who have been hypothyroid for only a few months): Oral: ~1.7 mcg/kg/day; usual doses are ≤200 mcg/day (range: 100-125 mcg/day for a 70 kg adult); doses ≥300 mcg/day are rare (consider poor compliance, malabsorption, and/or drug interactions). Titrate dose every 6 weeks. Patients >50 years or patients with cardiac disease: Refer to elderly dosing. I.M., I.V.: 50% of the oral dose Severe hypothyroidism: Oral: Initial: 12.5-25 mcg/day; adjust dose by 25 mcg/day every 2-4 weeks as appropriate Subclinical hypothyroidism (if treated): Oral: 1 mcg/kg/day TSH suppression: Oral: Well-differentiated thyroid cancer: Highly individualized; Doses >2 mcg/kg/day may be needed to suppress TSH to <0.1 mIU/mL. High-risk tumors may need a target level of <0.01 mIU/mL for TSH suppression. Benign nodules and nontoxic multinodular goiter: Routine use of T4 for TSH suppression is not recommended in patients with benign thyroid nodules. In patients deemed appropriate candidates, treatment should never be fully suppressive (TSH <0.1 mIU/mL) (Gharib, 2006; Cooper, 2006). Note: Avoid use if TSH is already suppressed. Myxedema coma or stupor: I.V.: 200-500 mcg, then 100-300 mcg the next day if necessary; smaller doses should be considered in patients with cardiovascular disease Dosing: Elderly Doses should be adjusted based on clinical response and laboratory parameters. Hypothyroidism: Elderly patients may require <1 mcg/kg/day: Oral: >50 years without cardiac disease or <50 years with cardiac disease: Initial: 25-50 mcg/day; adjust dose at 6- to 8-week intervals as needed >50 years with cardiac disease: Initial: 12.5-25 mcg/day; adjust dose by 12.5-25 mcg increments at 4- to 6-week intervals (many clinicians prefer to adjust at 6- to 8-week intervals). Note: Patients with combined hypothyroidism and cardiac disease should be monitored carefully for changes in stability. I.M., I.V.: 50% of the oral dose Myxedema coma:I.V.: Refer to adult dosing; lower doses may be needed. Dosing: Pediatric Hypothyroidism: Neonates, Infants, and Children: Doses should be adjusted based on clinical response and laboratory parameters. Oral: Daily dosage based on body weight and age as listed below: 0-3 months: 10-15 mcg/kg/day; if the infant is at risk for development of cardiac failure, use a lower starting dose of 25 mcg/day; if the initial serum T4 is very low (<5 mcg/dL) begin treatment at a higher dosage of 50 mcg/day 3-6 months: 8-10 mcg/kg/day or 25-50 mcg/day 6-12 months: 6-8 mcg/kg/day or 50-75 mcg/day 1-5 years: 5-6 mcg/kg/day or 75-100 mcg/day 6-12 years: 4-5 mcg/kg/day or 100-125 mcg/day >12 years: 2-3 mcg/kg/day or ≥150 mcg/day Growth and puberty complete: 1.7 mcg/kg/day; refer to adult dosing. Note: Hyperactivity in older children may be minimized by starting at 1/4 of the recommended dose and increasing each week by that amount until the full dose is achieved (4 weeks). Children with severe or chronic hypothyroidism should be started at 25 mcg/day; adjust dose by 25 mcg every 2-4 weeks. I.M., I.V.: 50% of the oral dose Available Products Excipient information presented when available (limited, particularly for generics); consult specific product labeling. Injection, powder for reconstitution, as sodium: 200 mcg, 500 mcg Tablet, oral, as sodium: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg Levothroid®: 25 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg [scored] Levothroid®: 50 mcg [scored; dye free] Levoxyl®: 25 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg [scored] Levoxyl®: 50 mcg [scored; dye free] Synthroid®: 25 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg [scored] Synthroid®: 50 mcg [scored; dye free] Unithroid®: 25 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg [scored] Unithroid®: 50 mcg [scored; dye free] Administration Administration, Oral Administer in the morning on an empty stomach, at least 30 minutes before food. Tablets may be crushed and suspended in 1-2 teaspoonfuls of water; suspension should be used immediately. Levoxyl® should be administered with a full glass of water to prevent gagging (due to tablet swelling). Administration, I.V. Dilute vial with 5 mL normal saline; use immediately after reconstitution; do not mix with other I.V. fluids Administration, I.V. Detail Dilute vial with 5 mL normal saline. Use immediately after reconstitution. I.V. form must be prepared immediately prior to administration. Should not be admixed with other solutions. Storage & Compatibility Storage Store tablets and injection at room temperature of 15°C to 30°C (59°F to 86°F). Protect tablets from light and moisture. Additional stability data: Stability in polypropylene syringes (100 mcg/mL in NS) at 5°C ± 1°C is 7 days (Gupta, 2000). Reconstitution Dilute vial for injection with 5 mL normal saline. Reconstituted concentrations for the 200 mcg and 500 mcg vials are 40 mcg/mL and 100 mcg/mL, respectively. Shake well and use immediately after reconstitution (manufacturer recommendation); discard any unused portions. I.V. Compatibility Do not mix I.V. solution with other I.V. infusion solutions. Monitoring Monitoring Parameters Thyroid function test (serum thyroxine, thyrotropin concentrations), resin triiodothyronine uptake (rT3U), free thyroxine index (FTI), T4, TSH, heart rate, blood pressure, clinical signs of hypo- and hyperthyroidism; TSH is the most reliable guide for evaluating adequacy of thyroid replacement dosage. TSH may be elevated during the first few months of thyroid replacement despite patients being clinically euthyroid. In cases where T4 remains low and TSH is within normal limits, an evaluation of “free” (unbound) T4 is needed to evaluate further increase in dosage Infants: Monitor closely for cardiac overload, arrhythmias, and aspiration from avid suckling Infants/children: Monitor closely for under/overtreatment. Undertreatment may decrease intellectual development and linear growth, and lead to poor school performance due to impaired concentration and slowed mentation. Overtreatment may adversely affect brain maturation, accelerate bone age (leading to premature closure of the epiphyses and reduced adult height); craniosynostosis has been reported in infants. Treated children may experience a period of catch-up growth. Monitor TSH and total or free T4 at 2 and 4 weeks after starting treatment; every 1-2 months for first year of life; every 2-3 months during years 1-3; every 3-12 months until growth completed. Perform routine clinical examinations at regular intervals (to assess mental and physical growth and development). Adults: Monitor TSH every 6-8 weeks until normalized; 8-12 weeks after dosage changes; every 6-12 months throughout therapy Reference Range Pediatrics: Cord T4 and values in the first few weeks are much higher, falling over the first months and years. ≥10 years: ~5.8-11 mcg/dL (SI: 75-142 nmol/L). Borderline low: ≤4.5-5.7 mcg/dL (SI: 58-73 nmol/L); low: ≤4.4 mcg/dL (SI: 57 nmol/L); results <2.5 mcg/dL (SI: <32 nmol/L) are strong evidence for hypothyroidism. Approximate adult normal range: 4-12 mcg/dL (SI: 51-154 nmol/L). Borderline high: 11.1-13 mcg/dL (SI: 143-167 nmol/L); high: ≥13.1 mcg/dL (SI: 169 nmol/L). Normal range is increased in women on birth control pills (5.5-12 mcg/dL); normal range in pregnancy: ~5.5-16 mcg/dL (SI: ~71-206 nmol/L). TSH: 0.4-10 (for those ≥80 years) mIU/L; T4: 4-12 mcg/dL (SI: 51-154 nmol/L); T3 (RIA) (total T3): 80-230 ng/dL (SI: 1.2-3.5 nmol/L); T4 free (free T4): 0.7-1.8 ng/dL (SI: 9-23 pmol/L). Breast-Feeding Considerations Minimally excreted in human milk; adequate levels are needed to maintain normal lactation Patient Education Consult prescriber before taking new medication or herbal products during therapy; some other medications or herbals may cause adverse effects with levothyroxine. Thyroid replacement therapy is generally for life. Take as directed, in the morning 30 minutes before breakfast. Do not take antacids or iron preparations within 4 hours of thyroid medication. Do not change brands and do not discontinue without consulting prescriber. Report chest pain, rapid heart rate, palpitations, heat intolerance, excessive sweating, increased nervousness, agitation, or lethargy. Dietary Implications Should be taken on an empty stomach, at least 30 minutes before food. View the Patient Handout: English | Spanish Additional Information Equivalent doses: The following statement on relative potency of thyroid products is included in a joint statement by American Thyroid Association (ATA), American Association of Clinical Endocrinologists (AACE) and The Endocrine Society (TES): For purposes of conversion, levothyroxine sodium (T4) 100 mcg is usually considered equivalent to desiccated thyroid 60 mg, thyroglobulin 60 mg, or liothyronine sodium (T3) 25 mcg. However, these are rough guidelines only and do not obviate the careful re-evaluation of a patient when switching thyroid hormone preparations, including a change from one brand of levothyroxine to another. Joint position statement is available at http://www.thyroid.org/professionals/advocacy/04_12_08_thyroxine.html. Note: Several medications have effects on thyroid production or conversion. The impact in thyroid replacement has not been specifically evaluated, but patient response should be monitored: Methimazole: Decreases thyroid hormone secretion, while propylthiouracil decrease thyroid hormone secretion and decreases conversion of T4 to T3. Beta-adrenergic antagonists: Decrease conversion of T4 to T3 (dose related, propranolol ≥160 mg/day); patients may be clinically euthyroid. Iodide, iodine-containing radiographic contrast agents may decrease thyroid hormone secretion; may also increase thyroid hormone secretion, especially in patients with Graves' disease. Other agents reported to impact on thyroid production/conversion include aminoglutethimide, amiodarone, chloral hydrate, diazepam, ethionamide, interferon-alpha, interleukin-2, lithium, lovastatin (case report), glucocorticoids (dose-related), mercaptopurine, sulfonamides, thiazide diuretics, and tolbutamide. In addition, a number of medications have been noted to cause transient depression in TSH secretion, which may complicate interpretation of monitoring tests for levothyroxine, including corticosteroids, octreotide, and dopamine. Metoclopramide may increase TSH secretion References Bauer LA, “Simulations of Levothyroxine Bioavailability Using a Single Dose Protocol,” Am J Ther, 1995, 2:414-6. [PMID: 11850686] Berkner PD, Starkman H, and Person N, “Acute L-Thyroxine Overdose: Therapy With Sodium Ipodate: Evaluation of Clinical and Physiologic Parameters,” J Emerg Med, 1991, 9(3):129-31. [PMID: 2050969] Binimelis J, Bassas L, Marruecos L, et al, “Massive Thyroxine Intoxication: Evaluation of Plasma Extraction,” Intensive Care Med, 1987, 13(1):33-8. [PMID: 3558934] Cooper DS, Doherty GM, Haugen BR, et al, for the ATA Guidelines Task Force, “Management Guidelines for Patients With Thyroid Nodules and Differentiated Thyroid Cancer,” Thyroid, 2006, 16(2):109-42. [PMID: 16420177] de Groot JW, Zonnenberg BA, Plukker JT, et al, “Imatinib Induces Hypothyroidism in Patients Receiving Levothyroxine,” Clin Pharmacol Ther, 2005, 78(4):433-8. [PMID: 16198662] Escalante DA, Arem N, and Arem R, “Assessment of Interchangeability of Two Brands of Levothyroxine Preparations With a Third-Generation TSH Assay,” Am J Med, 1995, 98(4):374-8. [PMID: 7709950] Gharib H, Papini E, Valcavi R, et al, for the AACE/AME Task Force on Thyroid Nodules, “American Association of Clinical Endocrinologists and Associazione Medici Endocrinologi Medical Guidelines for Clinical Practice for the Diagnosis and Management of Thyroid Nodules,” Endocr Pract , 2006, 12(1):63-102. [PMID: 16596732] Gorman RL, Chamberlain JM, Rose SR, et al, “Massive Levothyroxine Overdose: High Anxiety - Low Toxicity,” Pediatrics, 1988, 82(4):666-9. [PMID: 3174321] Gupta VD, “Stability of Levothyroxine Sodium Injection in Polypropylene Syringes,” Int J Pharm Compound, 2000, 4(6):482-3. Helfand M and Crapo LM, “Monitoring Therapy in Patients Taking Levothyroxine,” Ann Intern Med, 1990, 113(6):450-4. [PMID: 2143640] Johnson DG and Campbell S, “Hormonal and Metabolic Agents,” Geriatric Pharmacology, Bressler R and Katz MD, eds, New York, NY: McGraw-Hill, 1993, 427-50. Kulig K, Golightly LK, and Rumack BH, “Levothyroxine Overdose Associated With Seizures in a Young Child,” JAMA, 1985, 254(15):2109-10. [PMID: 4046139] Mandel SH, Magnusson AR, Burton BT, et al, “Massive Levothyroxine Ingestion: Conservative Management,” Clin Pediatr (Phila), 1989, 28(8):374-6. [PMID: 2758719] Mayor GH, Orlando T, and Kurtz N, “Limitations of Levothyroxine Bioequivalence Evaluation: Analysis of an Attempted Study,” Am J Ther, 1995, 2:417-32. [PMID: 11850687] Rosendale JD, Kauffman HM, McBride MA, et al, “Aggressive Pharmacologic Donor Management Results in More Transplanted Organs,” Transplantation, 2003, 75(4):482-7. [PMID: 12605114] Rosengard BR, Feng S, Alfrey EJ, et al, “Report of the Crystal City Meeting to Maximize the Use of Organs Recovered From the Cadaver Donor,” Am J Transplant, 2002, 2(8):701-11. [PMID: 12243491] Salim A, Martin M, Brown C, et al, “Using Thyroid Hormone in Brain-Dead Donors to Maximize the Number of Organs Available for Transplantation,” Clin Transplant, 2007, 21(3):405-9. [PMID: 17488392 ] Sanders LR, “Pituitary, Thyroid, Adrenal and Parathyroid Diseases in the Elderly,” Geriatric Medicine, 1990, 475-87. Sawin CT, Geller A, Hershman JM, et al, “The Aging Thyroid. The Use of Thyroid Hormone in Older Persons,” JAMA, 1989, 261(18):2653-5. [PMID: 2709545] Singh N, Singh P, and Hershman J. “Effect of Calcium Carbonate on the Absorption of Levothyroxine,” JAMA, 2000, 283:2822-25. [PMID: 10838651] Stockley IH, Drug Interactions, 5th ed, London, UK: Pharmaceutical Press, 1999. Tunget CL, Clark RF, Turchen SG, et al, “Raising the Decontamination Level for Thyroid Hormone Ingestions,” Am J Emerg Med, 1995, 13(1):9-13. [PMID: 7832964] Watts NB, “Use of a Sensitive Thyrotropin Assay for Monitoring Treatment With Levothyroxine,” Arch Intern Med, 1989, 149(2):309-12. [PMID: 2644903] AccessPharmacy © 1978-Present McGraw-Hill and/or its respective owners.
