Dosing & Uses
Dosage Forms & Strengths
tablet (Levo-T, Levoxyl, Unithroid, generic)
- 25mcg, 50mcg, 75mcg, 88mcg, 100mcg, 112mcg
- 125mcg, 137mcg, 150mcg, 175mcg, 200mcg, 300mcg
capsule (Tirosint, generic)
- 13mcg, 25mcg, 50mcg, 75mcg, 88mcg
- 100mcg, 112 mcg, 125mcg, 137 mcg, 150mcg
oral solution
-
Tirosint-SOL
- 13mcg/mL, 25mcg/mL, 37.5mcg/mL, 44mcg/mL, 50mcg/mL, 62.5mcg/mL
- 75mcg/mL, 88mcg/mL, 100mcg/mL, 112mcg/mL, 125mcg/mL, 137mcg/mL
- 150mcg/mL, 175mcg/mL, 200mcg/mL
-
Thyquidity
- 20mcg/mL
injection, lyophilized powder for reconstitution
- 100mcg/vial
- 200mcg/vial
- 500mcg/vial
Mild Hypothyroidism
1.7 mcg/kg or 100-125 mcg PO qDay; not to exceed 300 mcg/day
>50 years (or <50 yr with CV disease)
- Usual initial dose: 25-50 mcg/day
- May adjust dose by 12.5-25 mcg q6-8Week
>50 years with CV disease
- Usual initial dose: 12.5-25 mcg PO qDay
- May adjust dose by 12.5-25 mcg q4-6weeks until patient becomes euthyroid and serum TSH concentration normalized; adjustments q6-8weeks also used
- Dose range: 100-125 mcg PO qDay
Severe Hypothyroidism
Initial: 12.5-25 mcg PO qDay
Adjust dose by 25 mcg/day q2-4Week PRN
Subclinical Hypothyroidism
Initial: 1 mcg/kg PO qDay may be adequate, OR
If replacement therapy not initiated, monitor patient annually for clinical status
Myxedema Coma
300-500 mcg IV once, THEN 50-100 mcg qDay until patient is able to tolerate oral administration; may consider smaller doses in patients with cardiovascular disease
Organ Preservation (Orphan)
Preservation of organ function in brain-dead organ donors
Orphan indication sponsor
- Fera Pharmaceuticals, LLC; 134 Birch Hill Road; Locust Valley, NY 11560
Dosing Considerations
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
Monitor serum thyroid levels; patient may be asymptomatic
Monitoring
- Initially evaluate patients q6-8Week
- Once normalization of thyroid function and serum TSH conc achieved, evaluate q6-12mo
Dosage Forms & Strengths
Dosage Forms & Strengths
tablet (Levo-T, Levoxyl, Unithroid, generic)
- 25mcg, 50mcg, 75mcg, 88mcg, 100mcg, 112mcg
- 125mcg, 137mcg, 150mcg, 175mcg, 200mcg, 300mcg
capsule (Tirosint, generic)
- 13mcg, 25mcg, 50mcg, 75mcg, 88mcg
- 100mcg, 112 mcg, 125mcg, 137 mcg, 150mcg
oral solution
-
Tirosint-SOL
- 13mcg/mL, 25mcg/mL, 37.5mcg/mL, 44mcg/mL, 50mcg/mL, 62.5mcg/mL
- 75mcg/mL, 88mcg/mL, 100mcg/mL, 112mcg/mL, 125mcg/mL, 137mcg/mL
- 150mcg/mL, 175mcg/mL, 200mcg/mL
-
Thyquidity
- 20mcg/mL
injection, lyophilized powder for reconstitution
- 100mcg/vial
- 200mcg/vial
Hypothyroidism
Age 1-3 months
- 10-15 mcg/kg/day PO
- 5-7.5 mcg/kg/day IV/IM
- Use lower starting dose (25 mcg/day) if patient at risk of cardiac failure; if initial serum T4 lower than 5 mcg/dL begin treatment at higher dose (50 mcg/day)
Age 3-6 months
Age 6-12 months
Age 1-5 years
Age 6-12 years
>12 years
Dosing considerations
- Check for bioequivalence if switching brands/generics
- May minimize hyperactivity in older children by initiating dose at 1/4 of recommended dose; increase by that amount each week until full dose achieved
- Start children with severe or chronic hypothyroidism at 25 mcg/day; adjust dose by 25 mcg qweek
Because of increased prevalence of cardiovascular disease among the elderly, initiate therapy at less than full replacement dose; atrial arrhythmias can occur in elderly patients; atrial fibrillation is the most common of arrhythmias observed with levothyroxine overtreatment in the elderly
Interactions
Interaction Checker
No Results
Contraindicated
Serious - Use Alternative
Significant - Monitor Closely
Minor
Contraindicated (2)
- sodium iodide I-131
levothyroxine will decrease the level or effect of sodium iodide I-131 by Other (see comment). Contraindicated. Use of thyroid products or iodine before and during treatment with sodium iodide I-131 decreases uptake of sodium iodide I-131 by the thyroid gland
- sucroferric oxyhydroxide
sucroferric oxyhydroxide decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Contraindicated. No interaction anticipated with parenteral levothyroxine.
Serious - Use Alternative (12)
- antithrombin alfa
levothyroxine increases effects of antithrombin alfa by pharmacodynamic synergism. Avoid or Use Alternate Drug.
- antithrombin III
levothyroxine increases effects of antithrombin III by pharmacodynamic synergism. Avoid or Use Alternate Drug.
- argatroban
levothyroxine increases effects of argatroban by pharmacodynamic synergism. Avoid or Use Alternate Drug.
- bemiparin
levothyroxine increases effects of bemiparin by pharmacodynamic synergism. Avoid or Use Alternate Drug.
- bivalirudin
levothyroxine increases effects of bivalirudin by pharmacodynamic synergism. Avoid or Use Alternate Drug.
- bremelanotide
bremelanotide will decrease the level or effect of levothyroxine by Other (see comment). Avoid or Use Alternate Drug. Bremelanotide may slow gastric emptying and potentially reduces the rate and extent of absorption of concomitantly administered oral medications. Avoid use when taking any oral drug that is dependent on threshold concentrations for efficacy. Interactions listed are representative examples and do not include all possible clinical examples.
- fondaparinux
levothyroxine increases effects of fondaparinux by pharmacodynamic synergism. Avoid or Use Alternate Drug.
- heparin
levothyroxine increases effects of heparin by pharmacodynamic synergism. Avoid or Use Alternate Drug.
- lycopus
lycopus decreases effects of levothyroxine by pharmacodynamic antagonism. Contraindicated. Lycopus blocks peripheral conversion of T4 to T3.
- phenindione
levothyroxine increases effects of phenindione by pharmacodynamic synergism. Avoid or Use Alternate Drug.
- protamine
levothyroxine increases effects of protamine by pharmacodynamic synergism. Avoid or Use Alternate Drug.
- warfarin
levothyroxine increases effects of warfarin by pharmacodynamic synergism. Avoid or Use Alternate Drug.
Monitor Closely (43)
- apalutamide
apalutamide will decrease the level or effect of levothyroxine by increasing elimination. Use Caution/Monitor. Apalutamide induces UGT and may decrease systemic exposure of drugs that are UGT substrates.
- caffeine
caffeine decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. COFFEE binds levothyroxine in the GI tract. Separate by 2 hours.
- calcium acetate
calcium acetate decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate administration by 4 hours.
- calcium carbonate
calcium carbonate decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.
- calcium chloride
calcium chloride decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.
- calcium citrate
calcium citrate decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.
- calcium gluconate
calcium gluconate decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.
- carbonyl iron
carbonyl iron decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
- cholestyramine
cholestyramine decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
- colesevelam
colesevelam decreases levels of levothyroxine by drug binding in GI tract. Use Caution/Monitor. Concomitant administration decreases levothyroxine absorption; however, absorption is not reduced when levothyroxine is administered 4 hr before colesevelam.
- crofelemer
crofelemer increases levels of levothyroxine by Other (see comment). Use Caution/Monitor. Comment: Crofelemer has the potential to inhibit transporters MRP2 and OATP1A2 at concentrations expected in the gut; unlikely to inhibit systemically because minimally absorbed.
- didanosine
didanosine will decrease the level or effect of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Applies to didanosine chewable tablets and powder for oral solution; administer 2 hr before or several hours after didanosine oral solution or chewable tablet administration
- digoxin
levothyroxine decreases effects of digoxin by unknown mechanism. Use Caution/Monitor.
- dulaglutide
dulaglutide, levothyroxine. Other (see comment). Use Caution/Monitor. Comment: Dulaglutide slows gastric emptying and may impact absorption of concomitantly administered oral medications; be particularly cautious when coadministered with drugs that have a narrow therapeutic index.
- eluxadoline
eluxadoline increases levels of levothyroxine by decreasing metabolism. Use Caution/Monitor. Eluxadoline may increase the systemic exposure of coadministered OATP1B1 substrates.
- epinephrine
levothyroxine will increase the level or effect of epinephrine by unspecified interaction mechanism. Use Caution/Monitor.
- ferric maltol
ferric maltol decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
ferric maltol, levothyroxine. Either increases effects of the other by unspecified interaction mechanism. Modify Therapy/Monitor Closely. Coadministration of ferric maltol with certain oral medications may decrease the bioavailability of either ferric maltol and some oral drugs. For oral drugs where reductions in bioavailability may cause clinically significant effects on its safety or efficacy, separate administration of ferric maltol from these drugs. Duration of separation may depend on the absorption of the medication concomitantly administered (eg, time to peak concentration, whether the drug is an immediate or extended release product). - ferrous fumarate
ferrous fumarate decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
- ferrous gluconate
ferrous gluconate decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
- ferrous sulfate
ferrous sulfate decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
- food
food decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. COFFEE binds levothyroxine in the GI tract. Separate by 2 hours.
- insulin degludec
levothyroxine decreases effects of insulin degludec by pharmacodynamic antagonism. Use Caution/Monitor. Thyroid hormones regulate carbohydrate metabolism, gluconeogenesis, and glycogen stores mobilization; dose of antidiabetic agents may need adjustment and increased frequency of glucose monitoring may be required.
- insulin degludec/insulin aspart
levothyroxine decreases effects of insulin degludec/insulin aspart by pharmacodynamic antagonism. Use Caution/Monitor. Thyroid hormones regulate carbohydrate metabolism, gluconeogenesis, and glycogen stores mobilization; dose of antidiabetic agents may need adjustment and increased frequency of glucose monitoring may be required.
- insulin inhaled
levothyroxine decreases effects of insulin inhaled by pharmacodynamic antagonism. Use Caution/Monitor. Thyroid hormones regulate carbohydrate metabolism, gluconeogenesis, and glycogen stores mobilization; dose of antidiabetic agents may need adjustment and increased frequency of glucose monitoring may be required.
- iron dextran complex
iron dextran complex decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
- iron sucrose
iron sucrose decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
- ketamine
levothyroxine increases toxicity of ketamine by unspecified interaction mechanism. Use Caution/Monitor. Coadministration may cause marked hypertension and tachycardia.
- lanthanum carbonate
lanthanum carbonate decreases levels of levothyroxine by cation binding in GI tract. Use Caution/Monitor. Administer oral thyroid products at least 2 hr before or after lanthanum. Interaction applies only to oral thyroid products only. .
- letermovir
letermovir increases levels of levothyroxine by Other (see comment). Use Caution/Monitor. Comment: Letermovir, an OATP1B1/3 inhibitor may increase plasma concentrations of coadministered OATP1B1/3 substrates.
- levonorgestrel oral/ethinylestradiol/ferrous bisglycinate
levonorgestrel oral/ethinylestradiol/ferrous bisglycinate will decrease the level or effect of levothyroxine by unknown mechanism. Modify Therapy/Monitor Closely. The estrogen component of combined hormonal contraceptives (CHCs) may raise the serum concentrations of thyroxine-binding globulin. Women on thyroid hormone replacement therapy may need increased doses of thyroid hormone with use of CHCs.
- magnesium supplement
magnesium supplement will decrease the level or effect of levothyroxine by Other (see comment). Modify Therapy/Monitor Closely. Drug may adsorb to magnesium; may decrease absorption by the intestinal tract; applies to oral forms; may separate administration of drugs by 4 hr
- metformin
levothyroxine decreases effects of metformin by pharmacodynamic antagonism. Use Caution/Monitor. Patient should be closely observed for loss of blood glucose control; when drugs are withdrawn from a patient receiving metformin, patient should be observed closely for hypoglycemia.
- nateglinide
levothyroxine decreases effects of nateglinide by pharmacodynamic antagonism. Use Caution/Monitor. Coadministration may reduce nateglinide's hypoglycemic action.
- orlistat
orlistat decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Risk of hypothyroidism. Separate by 4 hours.
- patiromer
patiromer will decrease the level or effect of levothyroxine by drug binding in GI tract. Use Caution/Monitor. May administer 3 hours apart
- polysaccharide iron
polysaccharide iron decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
- raloxifene
raloxifene decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
- rose hips
rose hips decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
- sodium sulfate/?magnesium sulfate/potassium chloride
sodium sulfate/?magnesium sulfate/potassium chloride decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Administer levothyroxine at least 4 hr after each dose to avoid chelation with magnesium. .
- sodium sulfate/potassium sulfate/magnesium sulfate
sodium sulfate/potassium sulfate/magnesium sulfate decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Administer levothyroxine at least 4 hr after each dose to avoid chelation with magnesium. .
- teduglutide
teduglutide increases levels of levothyroxine by Other (see comment). Use Caution/Monitor. Comment: Teduglutide may increase absorption of concomitant PO medications; caution with with drugs requiring titration or those with a narrow therapeutic index; dose adjustment may be necessary.
- trimagnesium citrate anhydrous
trimagnesium citrate anhydrous decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
- ustekinumab
ustekinumab, levothyroxine. Other (see comment). Use Caution/Monitor. Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, normalizing the formation of CYP450 enzymes. Upon initiation or discontinuation of ustekinumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.
Minor (31)
- alendronate
levothyroxine decreases levels of alendronate by unspecified interaction mechanism. Minor/Significance Unknown. Bioavailability of alendronate decreases slightly.
- amobarbital
amobarbital decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- butabarbital
butabarbital decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- butalbital
butalbital decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- carbamazepine
carbamazepine decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- colestipol
colestipol decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- dexlansoprazole
dexlansoprazole decreases levels of levothyroxine by increasing gastric pH. Applies only to oral form of both agents. Minor/Significance Unknown. Conflicting evidence regarding this interaction exists.
- eptifibatide
levothyroxine decreases levels of eptifibatide by increasing renal clearance. Minor/Significance Unknown.
- eslicarbazepine acetate
eslicarbazepine acetate decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- esomeprazole
esomeprazole decreases levels of levothyroxine by increasing gastric pH. Applies only to oral form of both agents. Minor/Significance Unknown. Conflicting evidence regarding this interaction exists.
- ethotoin
ethotoin decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
ethotoin decreases levels of levothyroxine by plasma protein binding competition. Minor/Significance Unknown. - fosphenytoin
fosphenytoin decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
fosphenytoin decreases levels of levothyroxine by plasma protein binding competition. Minor/Significance Unknown. - furosemide
furosemide increases toxicity of levothyroxine by Other (see comment). Minor/Significance Unknown. Comment: High doses (greater than 80 mg) of furosemide may inhibit binding of thyroid hormones to carrier proteins and result in transient increase in free thyroid hormones, followed by overall decrease in total thyroid hormone levels.
- glandular products
glandular products increases effects of levothyroxine by pharmacodynamic synergism. Minor/Significance Unknown. Additive effects with thyroid glandular extract.
- guggul
guggul decreases effects of levothyroxine by pharmacodynamic antagonism. Minor/Significance Unknown.
- lansoprazole
lansoprazole decreases levels of levothyroxine by increasing gastric pH. Applies only to oral form of both agents. Minor/Significance Unknown. Conflicting evidence regarding this interaction exists.
- omeprazole
omeprazole decreases levels of levothyroxine by increasing gastric pH. Applies only to oral form of both agents. Minor/Significance Unknown. Conflicting evidence regarding this interaction exists.
- oxcarbazepine
oxcarbazepine decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- pantoprazole
pantoprazole decreases levels of levothyroxine by increasing gastric pH. Applies only to oral form of both agents. Minor/Significance Unknown. Conflicting evidence regarding this interaction exists.
- pentobarbital
pentobarbital decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- phenobarbital
phenobarbital decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- phenytoin
phenytoin decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
phenytoin decreases levels of levothyroxine by plasma protein binding competition. Minor/Significance Unknown. - piracetam
piracetam, levothyroxine. Mechanism: unknown. Minor/Significance Unknown. Combination of piracetam and T3+T4 produced confusion, sleep disorder in single case.
- primidone
primidone decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- rabeprazole
rabeprazole decreases levels of levothyroxine by increasing gastric pH. Applies only to oral form of both agents. Minor/Significance Unknown. Conflicting evidence regarding this interaction exists.
- rifampin
rifampin decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- secobarbital
secobarbital decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- shepherd's purse
shepherd's purse decreases effects of levothyroxine by unspecified interaction mechanism. Minor/Significance Unknown. Theoretical interaction.
- sodium polystyrene sulfonate
sodium polystyrene sulfonate decreases levels of levothyroxine by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- theophylline
levothyroxine decreases levels of theophylline by increasing elimination. Minor/Significance Unknown.
- tirofiban
levothyroxine decreases levels of tirofiban by increasing renal clearance. Minor/Significance Unknown.
Adverse Effects
Frequency Not Defined
Angina pectoris
Arthralgia
Congestive heart failure
Flushing
Increased pulse
Myocardial infarction
Palpitations
Arrhythmias
Cramps
Diarrhea
Nervousness
Anxiety
Choking sensation
Emotional lability
Headache
Heat intolerance
Insomnia
Myasthenia
Pseudomotor cerebri
Alopecia
Weight loss
Infertility
Dyspnea
Fever
Tachycardia
Tremor
Decreased bone mineral density
Postmarketing Reports
Musculoskeletal: Muscle weakness, muscle spasm
Dermatologic: Hair loss, rash
Slipped capital femoral epiphysis (children)
Warnings
Black Box Warnings
Thyroid hormones, either alone or with other therapeutic agents, should not be used for the 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
Contraindications
Hypersensitivity to thyroid hormone or other ingredients
Acute MI, thyrotoxicosis, uncorrected adrenal insufficiency
Treatment of obesity or infertility
No contraindications reported by manufacturer for myxedema coma when treated with injection
Cautions
Avoid undertreatment or overtreatment, which may result in adverse effects
Proper dose titration and careful monitoring is critical to prevent persistence of hypothyroidism or development of hyperthyroidism
Use caution in cardiovascular disease, HTN, endocrine disorders, osteoporosis, or myxedema
Over-treatment with levothyroxine may cause increase in heart rate, cardiac wall thickness, and cardiac contractility; may precipitate angina or arrhythmias, particularly in patients with cardiovascular disease and in elderly patients; monitor patients receiving concomitant levothyroxine and sympathomimetic agents for signs and symptoms of coronary insufficiency; initiate lower dose in elderly, those with angina pectoris, cardiovascular disease, or in those with severe hypothyroidism
Over- or under-treatment with levothyroxine may have negative effects on growth and development, cardiovascular function, bone metabolism, reproductive function, cognitive function, emotional state, gastrointestinal function, and on glucose and lipid metabolism; titrate dose carefully and monitor response to titration to avoid these effects
Monitor for presence of drug or food interactions when using levothyroxine and adjust dose as necessary; symptoms may be exacerbated or aggravated in patients with diabetes mellitus and insipidus; addition of levothyroxine therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements
Use of oral thyroid hormone drug products is not recommended to treat myxedema coma; administer thyroid hormone products formulated for intravenous administration to treat myxedema coma; myxedema coma is a life-threatening emergency characterized by poor circulation and hypometabolism, and may result in unpredictable absorption of levothyroxine sodium from the gastrointestinal tract
Do NOT generally use levothyroxine sodium preparations interchangeably, due to narrow therapeutic index
Check for bioequivalence if switching brands/generics
Synthroid and unithroid tabs contain lactose
Not recommended for TSH suppression in patients with thyroid nodules
Levoxyl tabs swell in mouth: take with full glass of water to avoid choking
Avoid use in postmenopausal women >60 years with osteoporosis, cardiovascular disease, or systemic illness
Avoid use in patients with large thyroid nodules or long-standing goiters, or low-normal TSH levels
Long-term therapy decreases bone mineral density; use lowest dose in postmenopausal women and women using suppressive doses
Use caution in patients with adrenal insufficiency; may exacerbate symptoms or agravate them; treatment with glucocorticoids should precede levothyroxine therapy adrenal insufficiency present; initiation of thyroid hormone therapy prior to initiating glucocorticoid therapy may precipitate acute adrenal crisis in patients with adrenal insufficiency
Monitor for presence of drug or food interactions when using levothyroxine and adjust dose as necessary
Pregnancy & Lactation
Pregnancy
Experience with levothyroxine use in pregnant women, including data from post-marketing studies, have not reported increased rates of major birth defects or miscarriages; there are risks to mother and fetus associated with untreated hypothyroidism in pregnancy; since TSH levels may increase during pregnancy, TSH should be monitored and levothyroxine dosage adjusted during pregnancy; untreated maternal hypothyroidism may have adverse effect on fetal neurocognitive development
Maternal hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, gestational hypertension, pre-eclampsia, stillbirth, and premature delivery; untreated maternal hypothyroidism may have adverse effect on fetal neurocognitive development
Pregnancy may increase thyroid hormone requirements. serum TSH level should be monitored and the dosage adjusted during pregnancy; since postpartum TSH levels are similar to preconception values, the dosage should return to the pre-pregnancy dose immediately after delivery
Lactation
Limited published studies report that levothyroxine is present in human milk; however, there is insufficient information to determine effects of levothyroxine on breastfed infant and no available information on effects of levothyroxine on milk production; adequate levothyroxine treatment during lactation may normalize milk production in hypothyroid lactating mothers; developmental and health benefits of breastfeeding should be considered along with mother’s clinical need for levothyroxine and any potential adverse effects on breastfed infant from levothyroxine or from underlying maternal condition
Pregnancy Categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk. C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done. D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk. X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist. NA: Information not available.Pharmacology
Mechanism of Action
Synthetic T4; thyroid hormone increases basal metabolic rate, increases utilization and mobilization of glycogen stores, promotes gluconeogenesis; involved in growth development and stimulates protein synthesis
Absorption
40-80% from GI tract (PO)
Bioavailability: 64% (nonfasting); 79-81% (fasting)
Peak plasma time: 2-4 hr (PO)
Duration: Hypothyroidism, several weeks
Onset, hypothyroidism
- Initial response: 3-5 days (PO); 6-8 hr (IV)
- Maximum effect: Several weeks
- Peak effect: 24 hr (IV)
Onset, myxedema coma
- Initial response: 6-12 hr (IV)
- Peak effect: 24 hr
Distribution
Protein bound: 99%
Vd: 9-10 L
Metabolism
Deiodinated in blood and then 50% converted to active metabolite, triiodothyronine (T3), also by liver
Metabolites: T3 (active)
Elimination
Half-life: 9-10 days (hypothyroid); 3-4 days (hyperthyroid); 6-7 days (euthyroid)
Total body clearance: 0.8-1.4 L/day
Excretion: Urine (major), feces (20%)
Administration
IV Preparation
Add 5 mL of NS to vial containing 200 or 500 mcg and shake until a clear solution is obtained; resultant solutions contain approximately 40 or 100 mcg/mL, respectively
Use reconstituted solutions immediately; discard any unused portions
Alternatively, add 2 mL NS to vial containing 200 mcg to produce Synthroid solution containing approximately 100 mcg/mL
Do not admix with IV infusion solutions
Oral Administration
Take tabs with full glass of water preferably 30 min to 1 hr before breakfast on empty stomach
Do not use foods that decrease absorption (soybean products) for administering levothyroxine
Administer oral levothyroxine >4 hr apart from drugs known to interfere with absorption
IV/IM: Administer 50% of PO dose
Patients unable to swallow intact tabs
- Crush appropriate dose and place in 5-10 mL of water
- Administer resultant suspension by spoon or dropper immediately, do NOT store
Images
| BRAND | FORM. | UNIT PRICE | PILL IMAGE |
|---|---|---|---|
| Euthyrox oral - | 200 mcg tablet |  | |
| Euthyrox oral - | 175 mcg tablet |  | |
| Euthyrox oral - | 150 mcg tablet |  | |
| Euthyrox oral - | 137 mcg tablet |  | |
| Euthyrox oral - | 125 mcg tablet |  | |
| Euthyrox oral - | 112 mcg tablet |  | |
| Euthyrox oral - | 100 mcg tablet |  | |
| Euthyrox oral - | 88 mcg tablet |  | |
| Euthyrox oral - | 75 mcg tablet |  | |
| Euthyrox oral - | 50 mcg tablet |  | |
| Euthyrox oral - | 25 mcg tablet |  | |
| Levoxyl oral - | 200 mcg tablet |  | |
| Levoxyl oral - | 125 mcg tablet |  | |
| Levoxyl oral - | 112 mcg tablet |  | |
| Levoxyl oral - | 100 mcg tablet |  | |
| Levoxyl oral - | 88 mcg tablet |  | |
| Levoxyl oral - | 75 mcg tablet |  | |
| Levoxyl oral - | 50 mcg tablet |  | |
| Levoxyl oral - | 25 mcg tablet |  | |
| Levoxyl oral - | 175 mcg tablet |  | |
| Levoxyl oral - | 150 mcg tablet |  | |
| Levoxyl oral - | 137 mcg tablet |  | |
| Synthroid oral - | 25 mcg tablet |  | |
| Synthroid oral - | 137 mcg tablet |  | |
| Synthroid oral - | 150 mcg tablet |  | |
| Synthroid oral - | 75 mcg tablet |  | |
| Synthroid oral - | 50 mcg tablet |  | |
| Synthroid oral - | 100 mcg tablet |  | |
| Synthroid oral - | 100 mcg tablet |  | |
| Synthroid oral - | 125 mcg tablet |  | |
| Synthroid oral - | 112 mcg tablet |  | |
| Synthroid oral - | 125 mcg tablet |  | |
| Synthroid oral - | 300 mcg tablet |  | |
| Synthroid oral - | 200 mcg tablet |  | |
| Synthroid oral - | 175 mcg tablet |  | |
| Synthroid oral - | 150 mcg tablet |  | |
| Synthroid oral - | 88 mcg tablet |  | |
| Synthroid oral - | 75 mcg tablet |  | |
| Synthroid oral - | 50 mcg tablet |  | |
| Tirosint-Sol oral - | 200 mcg/mL solution |  | |
| Tirosint-Sol oral - | 200 mcg/mL solution |  | |
| Tirosint-Sol oral - | 175 mcg/mL solution |  | |
| Tirosint-Sol oral - | 150 mcg/mL solution |  | |
| Tirosint-Sol oral - | 125 mcg/mL solution |  | |
| Tirosint-Sol oral - | 112 mcg/mL solution |  | |
| Tirosint-Sol oral - | 175 mcg/mL solution |  | |
| Tirosint-Sol oral - | 150 mcg/mL solution |  | |
| Tirosint-Sol oral - | 137 mcg/mL solution |  | |
| Tirosint-Sol oral - | 137 mcg/mL solution |  | |
| Tirosint-Sol oral - | 125 mcg/mL solution |  | |
| Tirosint-Sol oral - | 112 mcg/mL solution |  | |
| Tirosint-Sol oral - | 100 mcg/mL solution |  | |
| Tirosint-Sol oral - | 88 mcg/mL solution |  | |
| Tirosint-Sol oral - | 100 mcg/mL solution |  | |
| Tirosint-Sol oral - | 88 mcg/mL solution |  | |
| Tirosint-Sol oral - | 75 mcg/mL solution |  | |
| Tirosint-Sol oral - | 75 mcg/mL solution |  | |
| Tirosint-Sol oral - | 50 mcg/mL solution |  | |
| Tirosint-Sol oral - | 50 mcg/mL solution |  | |
| Tirosint-Sol oral - | 25 mcg/mL solution |  | |
| Tirosint-Sol oral - | 13 mcg/mL solution |  | |
| Tirosint-Sol oral - | 13 mcg/mL solution |  | |
| Tirosint-Sol oral - | 25 mcg/mL solution |  | |
| levothyroxine oral - | 125 mcg tablet |  | |
| levothyroxine oral - | 100 mcg tablet |  | |
| levothyroxine oral - | 88 mcg tablet |  | |
| levothyroxine oral - | 112 mcg tablet |  | |
| levothyroxine oral - | 50 mcg tablet |  | |
| levothyroxine oral - | 137 mcg tablet |  | |
| levothyroxine oral - | 300 mcg tablet |  | |
| levothyroxine oral - | 200 mcg tablet |  | |
| levothyroxine oral - | 175 mcg tablet |  | |
| levothyroxine oral - | 150 mcg tablet |  | |
| levothyroxine oral - | 137 mcg tablet |  | |
| levothyroxine oral - | 125 mcg tablet |  | |
| levothyroxine oral - | 112 mcg tablet |  | |
| levothyroxine oral - | 100 mcg tablet |  | |
| levothyroxine oral - | 88 mcg tablet |  | |
| levothyroxine oral - | 75 mcg tablet |  | |
| levothyroxine oral - | 50 mcg tablet |  | |
| levothyroxine oral - | 25 mcg tablet |  | |
| levothyroxine oral - | 25 mcg tablet |  | |
| levothyroxine oral - | 75 mcg tablet |  | |
| levothyroxine oral - | 175 mcg tablet |  | |
| levothyroxine oral - | 75 mcg tablet |  | |
| levothyroxine oral - | 75 mcg tablet |  | |
| levothyroxine oral - | 88 mcg tablet |  | |
| levothyroxine oral - | 50 mcg tablet |  | |
| levothyroxine oral - | 25 mcg tablet |  | |
| levothyroxine oral - | 88 mcg tablet |  | |
| levothyroxine oral - | 112 mcg tablet |  | |
| levothyroxine oral - | 100 mcg tablet |  | |
| levothyroxine oral - | 137 mcg tablet |  | |
| levothyroxine oral - | 175 mcg tablet |  | |
| levothyroxine oral - | 112 mcg tablet |  | |
| levothyroxine oral - | 88 mcg tablet |  | |
| levothyroxine oral - | 125 mcg tablet |  | |
| levothyroxine oral - | 112 mcg tablet |  | |
| levothyroxine oral - | 25 mcg tablet |  | |
| levothyroxine oral - | 150 mcg tablet |  | |
| levothyroxine oral - | 100 mcg tablet |  | |
| levothyroxine oral - | 300 mcg tablet |  | |
| levothyroxine oral - | 200 mcg tablet |  | |
| levothyroxine oral - | 125 mcg tablet |  | |
| levothyroxine oral - | 100 mcg tablet |  | |
| levothyroxine oral - | 300 mcg tablet |  | |
| levothyroxine oral - | 200 mcg tablet |  | |
| levothyroxine oral - | 150 mcg tablet |  | |
| levothyroxine oral - | 175 mcg tablet |  | |
| levothyroxine oral - | 200 mcg tablet |  | |
| levothyroxine oral - | 300 mcg tablet |  | |
| levothyroxine oral - | 175 mcg tablet |  | |
| levothyroxine oral - | 150 mcg tablet |  | |
| levothyroxine oral - | 137 mcg tablet |  | |
| levothyroxine oral - | 50 mcg tablet |  | |
| levothyroxine oral - | 25 mcg tablet |  | |
| levothyroxine oral - | 75 mcg tablet |  | |
| levothyroxine oral - | 137 mcg tablet |  | |
| levothyroxine oral - | 112 mcg tablet |  | |
| levothyroxine oral - | 75 mcg tablet |  | |
| levothyroxine oral - | 150 mcg tablet |  | |
| levothyroxine oral - | 25 mcg tablet |  | |
| levothyroxine oral - | 125 mcg tablet |  | |
| levothyroxine oral - | 50 mcg tablet |  | |
| levothyroxine oral - | 175 mcg tablet |  | |
| levothyroxine oral - | 125 mcg tablet |  | |
| levothyroxine oral - | 100 mcg tablet |  | |
| levothyroxine oral - | 88 mcg tablet |  | |
| levothyroxine oral - | 50 mcg tablet |  | |
| levothyroxine oral - | 300 mcg tablet |  | |
| levothyroxine oral - | 200 mcg tablet |  | |
| Tirosint oral - | 200 mcg capsule |  | |
| Tirosint oral - | 100 mcg capsule |  | |
| Tirosint oral - | 88 mcg capsule |  | |
| Tirosint oral - | 25 mcg capsule |  | |
| Tirosint oral - | 175 mcg capsule |  | |
| Tirosint oral - | 137 mcg capsule |  | |
| Tirosint oral - | 112 mcg capsule |  | |
| Tirosint oral - | 13 mcg capsule |  | |
| Tirosint oral - | 125 mcg capsule |  | |
| Tirosint oral - | 100 mcg capsule |  | |
| Tirosint oral - | 50 mcg capsule |  | |
| Tirosint oral - | 25 mcg capsule |  | |
| Tirosint oral - | 150 mcg capsule |  | |
| Tirosint oral - | 75 mcg capsule |  | |
| Tirosint oral - | 88 mcg capsule |  | |
| Tirosint oral - | 75 mcg capsule |  | |
| Tirosint oral - | 50 mcg capsule |  | |
| Tirosint oral - | 13 mcg capsule |  | |
| Tirosint oral - | 150 mcg capsule |  | |
| Tirosint oral - | 137 mcg capsule |  | |
| Tirosint oral - | 112 mcg capsule |  | |
| Tirosint oral - | 125 mcg capsule |  | |
| Levo-T oral - | 175 mcg tablet | | |
| Levo-T oral - | 150 mcg tablet | | |
| Levo-T oral - | 137 mcg tablet | | |
| Levo-T oral - | 125 mcg tablet | | |
| Levo-T oral - | 112 mcg tablet | | |
| Levo-T oral - | 100 mcg tablet | | |
| Levo-T oral - | 88 mcg tablet | | |
| Levo-T oral - | 75 mcg tablet | | |
| Levo-T oral - | 50 mcg tablet | | |
| Levo-T oral - | 25 mcg tablet | | |
| Levo-T oral - | 300 mcg tablet | | |
| Levo-T oral - | 200 mcg tablet | | |
| Unithroid oral - | 150 mcg tablet |  | |
| Unithroid oral - | 125 mcg tablet | | |
| Unithroid oral - | 112 mcg tablet | | |
| Unithroid oral - | 100 mcg tablet | | |
| Unithroid oral - | 88 mcg tablet | | |
| Unithroid oral - | 75 mcg tablet | | |
| Unithroid oral - | 50 mcg tablet | | |
| Unithroid oral - | 25 mcg tablet | | |
| Unithroid oral - | 300 mcg tablet |  | |
| Unithroid oral - | 200 mcg tablet | | |
| Unithroid oral - | 175 mcg tablet | | |
| Unithroid oral - | 137 mcg tablet | | |
| levothyroxine intravenous - | 500 mcg vial |  | |
| levothyroxine intravenous - | 200 mcg vial |  | |
| levothyroxine intravenous - | 500 mcg vial |  | |
| levothyroxine intravenous - | 200 mcg vial |  | |
| levothyroxine intravenous - | 100 mcg vial |  | |
| levothyroxine intravenous - | 100 mcg vial |  | |
| levothyroxine intravenous - | 200 mcg vial |  | |
| levothyroxine intravenous - | 500 mcg vial |  | |
| levothyroxine intravenous - | 100 mcg vial |  |
Copyright © 2010 First DataBank, Inc.
Patient Handout
levothyroxine oral
LEVOTHYROXINE SOLUTION - ORAL
(LEE-voe-thye-ROX-een)
COMMON BRAND NAME(S): Thyquidity, Tirosint-Sol
WARNING: This medication should not be used for weight loss. Normal doses of this medication will not work for weight loss, and large doses of this medication may cause serious, possibly fatal side effects, especially when taken with diet pills.
USES: Levothyroxine is used to treat an underactive thyroid gland (hypothyroidism). It replaces or provides more thyroid hormone, which is normally produced by the 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 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 (such as certain types of goiters, thyroid cancer).This medication should not be used to treat infertility unless it is caused by low thyroid hormone levels.
HOW TO USE: Read the Patient Information Leaflet and Instructions for Use if available from your pharmacist before you start taking levothyroxine and each time you get a refill. If you have any questions, ask your doctor or pharmacist.Take this medication by mouth as directed by your doctor, usually once daily on an empty stomach, 30 minutes to 1 hour before breakfast.If you are using the medication that comes in a bottle, carefully measure the dose using a special measuring device/spoon. Do not use a household spoon because you may not get the correct dose. Take the medication directly from the measuring device. Do not mix with any other liquid.If you are using the medication that comes in an ampule, the medication may be taken by first mixing it in water, or it may be taken directly (without water). To take it by mixing in water, open the ampule as directed. Then turn the ampule upside down and slowly squeeze the soft (middle) part of the ampule to empty the contents into a glass or cup of water. Release pressure and wait a few seconds. Repeat squeezing and releasing the ampule at least 5 times, until no more liquid comes out of the ampule. Stir the solution and drink all of the liquid right away. Rinse the glass or cup with more water and drink to make sure you have taken all the medicine. Do not prepare a supply ahead of time. To take this medication directly, slowly squeeze the soft (middle) part of the open ampule to empty the contents into the mouth or onto a spoon. Release pressure and wait a few seconds. Repeat squeezing and releasing the ampule at least 5 times, until no more liquid comes out of the ampule. Take all of the liquid right away.The dosage is based on your age, weight, medical condition, and response to treatment.Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day.Do not stop taking this medication without consulting your doctor. Thyroid replacement treatment is usually taken for life.There are different brands of levothyroxine available. Do not change brands without first consulting your doctor or pharmacist.Certain medications (such as cholestyramine, colestipol, colesevelam, antacids, sucralfate, simethicone, iron, sodium polystyrene sulfonate, calcium supplements, orlistat, lanthanum, sevelamer, among others) can decrease the amount of thyroid hormone that is absorbed by your body. If you are taking any of these drugs, separate them from this medication by at least 4 hours.Symptoms of low thyroid hormone levels include tiredness, muscle aches, constipation, dry skin, weight gain, slow heartbeat, or sensitivity to cold. Tell your doctor if your condition does not get better or if it gets worse after several weeks of taking this medication.
SIDE EFFECTS: See also Precautions section.Hair loss may occur during the first few months of treatment. This effect is usually temporary as your body adjusts to this medication. If this effect lasts or gets worse, tell your doctor or pharmacist promptly.Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.Tell your doctor right away if you have any serious side effects, including: increased sweating, sensitivity to heat, mental/mood changes (such as nervousness, mood swings), tiredness, diarrhea, shaking (tremor), headache, shortness of breath, bone pain, easily broken bones.Get medical help right away if you have any very serious side effects, including: chest pain, fast/pounding/irregular heartbeat, swelling hands/ankles/feet, seizures.A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.In the US -Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
PRECAUTIONS: Before taking levothyroxine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.Before using this medication, tell your doctor or pharmacist your medical history, especially of: increased thyroid hormones (thyrotoxicosis), decreased adrenal gland function, heart disease (such as coronary artery disease, irregular heartbeat), high blood pressure, diabetes.If you have diabetes, this drug may affect your blood sugar. Check your blood sugar regularly as directed and share the results with your doctor. Tell your doctor right away if you have symptoms such as increased thirst/urination, shakiness, unusual sweating, dizziness, or hunger. Your doctor may need to adjust your diabetes medication, exercise program, or diet.Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).Children may be more sensitive to certain side effects of this drug, especially headache, vision changes, and hip/leg pain. High thyroid hormone levels may lead to decreased bone development/growth and reduced final adult height. Keep all lab/medical appointments so the doctor can monitor treatment.Older adults may be more sensitive to the side effects of this drug, especially fast/pounding/irregular heartbeat.This drug may be used during pregnancy. Tell your doctor if you are pregnant because your doctor may need to change your dose.Levothyroxine passes into breast milk but is unlikely to harm a nursing infant. Consult your doctor before breast-feeding.
DRUG INTERACTIONS: See also How to Use section.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 (including prescription/nonprescription drugs and herbal products) 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 are: "blood thinners" (such as warfarin), digoxin, sucroferric oxyhydroxide.
OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: fast/pounding/irregular heartbeat, loss of consciousness, confusion, seizures.
NOTES: Do not share this medication with others.Lab and/or medical tests (such as thyroid function) should be done while you are taking this medication. Keep all medical and lab appointments.
MISSED DOSE: If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up unless your doctor tells you to do so. Call your doctor if you miss 2 or more doses in a row. Ask your doctor ahead of time what to do about a missed dose and follow your doctor's specific directions.
STORAGE: Store at room temperature away from light and moisture. This medication comes in a bottle or in ampules. If the medication comes in a bottle, store the medication in the original bottle. Use the medication within 8 weeks after opening the bottle. Store ampules in the pouch until ready to use. The ampules should be used within 15 days after opening the pouch. Do not store in the bathroom. Keep all medications away from children and pets.Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.
Information last revised August 2021. Copyright(c) 2021 First Databank, Inc.
IMPORTANT: HOW TO USE THIS INFORMATION: This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.
Formulary
Adding plans allows you to compare formulary status to other drugs in the same class.
To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.
Adding plans allows you to:
- View the formulary and any restrictions for each plan.
- Manage and view all your plans together – even plans in different states.
- Compare formulary status to other drugs in the same class.
- Access your plan list on any device – mobile or desktop.
