Names and pronunciation
(lee-voe-thye-rox′een) Eltroxin , Euthyrox, Levoxyl, Synthroid, Tirosint, Tirosint-SOL, Unithroid
Source page 784
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Individual generic drug information
Extracted information for levothyroxine (T4) only.
(lee-voe-thye-rox′een) Eltroxin , Euthyrox, Levoxyl, Synthroid, Tirosint, Tirosint-SOL, Unithroid
Source page 784
Func. class.: Thyroid hormone
Source page 784
Chem. class.: Levoisomer of thyroxine
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Do not confuse: Synthroid/Symmetrel levothyroxine/lamotrigine/Lanoxin/ liothyronine/Loxitane
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ACTION: Increases metabolic rate; controls protein synthesis; increases car- diac output, renal blood flow, O2 con- sumption, body temperature, blood vol- ume, growth, development at cellular level via action on thyroid hormone receptors
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USES: Hypothyroidism, myxedema coma, thyroid hormone replacement, thyrotoxicosis, congenital hypothyroid- ism, some types of thyroid cancer, pitu- itary TSH suppression
Source page 784
Extracted information for levothyroxine (T4) only.
CONTRAINDICATIONS: Adrenal insufficiency, recent MI, thyrotoxicosis, hypersensitivity to beef, alcohol intoler- ance (inj only)
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Black Box Warning: Obesity treatment Precautions: Pregnancy, breastfeeding, geriatric patients, angina pectoris, hyper- tension, ischemia, cardiac disease, diabetes Black Box Warning: That product is not to be taken to reduce weight • To avoid OTC preparations with iodine; to read labels; to separate antacids, iron, calcium products by 4 hr • To take in AM on empty stomach, at least 30 min before food • To avoid iodine-rich food, iodized salt, soybeans, tofu, turnips, high-iodine sea- food, some bread products • That product is not a cure but controls symptoms; that treatment is lifelong, full effect may take up to 6 wk • That all products are not interchange- able • Pregnancy/breastfeeding: to continue using during pregnancy, breastfeeding • Anticoagulants: to have anticoagulant level monitored, dose adjusted as needed HIGH ALERT
Source pages 784, 786
SIDE EFFECTS CNS: Anxiety, insomnia, tremors, headache, thyroid storm, excitability CV: Tachycardia, palpitations, angina, dysrhythmias, hypertension, cardiac arrest GI: Nausea, diarrhea, increased or decreased appetite, cramps MISC: Menstrual irregularities, weight loss, sweating, heat intolerance, fever, alo- pecia, decreased bone mineral density
Source page 785
INTERACTIONS Increase: levothyroxine need—SSRIs, antiepileptics (carbamazepine, oxcar- bazepine, phenobarbital, primidone, phenytoin), antimicrobials (rifampin, efavirenz, rifabutin, rifapentine); monitor levels of levothyroxine Increase or Decrease: glucose levels— insulin, antidiabetics; monitor blood glu- cose, adjust levels Increase: cardiac insufficiency risk— EPINEPHrine products Increase: effects of both products—tri- cyclics, tetracyclics Increase: effects of anticoagulants, sym- pathomimetics, tricyclics; monitor PT, INR if using with anticoagulants Decrease: levothyroxine absorption— bile acid sequestrants, orlistat, ferrous sulfate Decrease: levothyroxine effect—estro- gens, antacids, sucralfate, aluminum, mag- nesium, calcium, iron, rifampin, rifabutin Drug/Herb Decrease: thyroid hormone effect—soy, horseradish Drug/Lab Test Increase: blood glucose Decrease: thyroid function tests Drug/Food Decrease: product absorption—fiber, walnuts; avoid concurrent use or adjust L dose
Source page 785
Extracted information for levothyroxine (T4) only.
DOSAGE AND ROUTES Hypothyroidism • Adult ≤50 yr: PO 1.6 mcg/kg/day, 6-8 wk, average dose 100-200 mcg/day; IM/IV 50-100 mcg/day as single dose or 50% of usual oral dosage • Adult >50 yr without heart disease or <50 yr with heart disease: PO 25-50 mcg/day, titrate q6-8wk • Adult >50 yr with heart disease: PO 12.5-25 mcg/day, titrate by 12.5-25 mcg q6-8wk • Child (puberty complete): PO 1.7 mcg/ kg/day • Child >12 yr (incomplete puberty): PO 2-3 mcg/kg/day as single dose in AM • Child 6-12 yr: PO 4-5 mcg/kg/day as single dose in AM • Child 1-5 yr: PO 5-6 mcg/kg/day as single dose in AM • Child 6-12 mo: PO 6-8 mcg/kg/day as single dose in AM • Child 3-6 mo: PO 8-10 mcg/kg/day as single dose in AM • Infant/neonate to age 3 mo: PO 10-15 mcg/kg/day; use in lower dose in those at risk for cardiac failure; may increase q4- 6wk if needed Myxedema coma • Adult: IV 300-500 mcg initially, may increase by 100-300 mcg after 24 hr; give oral medication as soon as possible Subclinical hypothyroidism • Adult: PO 1 mcg/kg/day
Source page 784
Available forms: Powder for inj 100, 200, 500 mcg/vial; tabs 25, 50, 88, 100, 112, 125, 137, 150, 175, 200, 300 mcg; cap (liquid filled) 13, 25, 50, 75, 88, 100, 112, 125, 137, 150 mcg
Source page 784
Administer: • Store in tight, light-resistant container; sol should be discarded if not used im- mediately • Withdrawal of medication 4 wk before RAIU test PO route • In AM if possible as single dose to de- crease sleeplessness; at same time each day to maintain product level; take on empty stomach • Only for hormone imbalances; not to be used for obesity, male infertility, men- strual conditions, lethargy • Use 8 oz of water on empty stomach • Lowest dose that relieves symptoms; lower dose to geriatric patients and for those with cardiac diseases • Crush and mix with water, nonsoy for- mula (decreased absorption), or breast milk for infants, children; give by spoon or dropper; may crush and sprinkle over applesauce or other food • Separate antacids, iron, calcium prod- ucts by 4 hr Direct IV route • IV after reconstituting with 5 mL nor- mal saline injection (500 mcg/5 mL, 200 mcg/2 mL); shake; give through Y-tube or 3-way stopcock; give ≤100 mcg/1 min; do not add to IV infusion • Considered to be incompatible in sy- ringe with all other products
Source pages 784, 785
Extracted information for levothyroxine (T4) only.
Assess: • B/P, pulse periodically during treat- ment • Weight daily in same clothing, using same scale, at same time of day • Height, growth rate of child • Patient may require decreased antico- agulant; check for bleeding, bruising • Cardiac status: angina, palpitation, chest pain, change in VS • CAD: monitor for coronary insuffi- ciency; also watch for cardiac changes in those receiving high, rapid dosing • Bone density: test bone density base- line and periodically; bone loss may oc- cur with long-term therapy • Pregnancy/breastfeeding: may be used in pregnancy and breastfeeding Hypothyroidism: • T3, T4, FTIs, which are decreased; ra- diommunoassay of TSH, which is in- creased; radio uptake, which is increased if patient is receiving too low a dose of medication • Increased nervousness, excitability, ir- ritability, which may indicate too high a dose of medication, usually after 1-3 wk of treatment
Source page 785
Evaluate: • Therapeutic response: absence of de- pression; increased weight loss, diuresis, pulse, appetite; absence of constipation, peripheral edema, cold intolerance; pale, cool, dry skin; brittle nails, alopecia, coarse hair, menorrhagia, night blindness, pares- thesias, syncope, stupor, coma, rosy cheeks
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CLINICAL CONSIDERATIONS
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Patient and caregiver information: • That hair loss will occur in child, is temporary; that hypothyroid child will show almost immediate behavior/per- sonality change • To report excitability, irritability, anxi- ety, which indicate overdose • Not to switch brands unless approved by prescriber; to protect from light, moisture
Source page 786
Extracted information for levothyroxine (T4) only.
PHARMACOKINETICS Half-life euthyroid 6-7 days, hypothyroid 9-10 days, hyperthyroid 3-4 days, distrib- uted throughout body tissues, protein binding 99% PO: Onset 24 hr IV: Onset 6-8 hr
Source page 785
Filter the extracted dose blocks for this individual drug.
Hypothyroidism
• Adult ≤50 yr: PO 1.6 mcg/kg/day, 6-8 wk, average dose 100-200 mcg/day; IM/IV 50-100 mcg/day as single dose or 50% of usual oral dosage
Candidate age grouping · source page 784
Hypothyroidism
• Adult >50 yr without heart disease or <50 yr with heart disease: PO 25-50 mcg/day, titrate q6-8wk
Candidate age grouping · source page 784
Hypothyroidism
• Adult >50 yr with heart disease: PO 12.5-25 mcg/day, titrate by 12.5-25 mcg q6-8wk
Candidate age grouping · source page 784
Hypothyroidism
• Child (puberty complete): PO 1.7 mcg/ kg/day
Candidate age grouping · source page 784
Hypothyroidism
• Child >12 yr (incomplete puberty): PO 2-3 mcg/kg/day as single dose in AM
Candidate age grouping · source page 784
Hypothyroidism
• Child 6-12 yr: PO 4-5 mcg/kg/day as single dose in AM
Candidate age grouping · source page 784
Hypothyroidism
• Child 1-5 yr: PO 5-6 mcg/kg/day as single dose in AM
Candidate age grouping · source page 784
Hypothyroidism
• Child 6-12 mo: PO 6-8 mcg/kg/day as single dose in AM
Candidate age grouping · source page 784
Hypothyroidism
• Child 3-6 mo: PO 8-10 mcg/kg/day as single dose in AM
Candidate age grouping · source page 784
Hypothyroidism
• Infant/neonate to age 3 mo: PO 10-15 mcg/kg/day; use in lower dose in those at risk for cardiac failure; may increase q4- 6wk if needed Myxedema coma
Candidate age grouping · source page 784
Hypothyroidism
• Adult: IV 300-500 mcg initially, may increase by 100-300 mcg after 24 hr; give oral medication as soon as possible Subclinical hypothyroidism
Candidate age grouping · source page 784
Hypothyroidism
• Adult: PO 1 mcg/kg/day
Candidate age grouping · source page 784