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Levothyroxine

 
Drug Info:

Levothyroxine

Home > Library > Health > Drug Info

Brand names: Estre™, Levo-T®, Levothroid®, Levoxyl®, Synthroid®, Thyro-Tabs®, Unithroid®

Chemical formula:



Levothyroxine Sodium Oral tablet

What is this medicine?

LEVOTHYROXINE (lee voe thye ROX een) is a thyroid hormone. This medicine can improve symptoms of thyroid deficiency such as slow speech, lack of energy, weight gain, hair loss, dry skin, and feeling cold. It also helps to treat goiter (an enlarged thyroid gland). It is also used to treat some kinds of thyroid cancer along with surgery and other medicines.
 
This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:
•angina
•blood clotting problems
•diabetes
•dieting or on a weight loss program
•fertility problems
•heart disease
•high levels of thyroid hormone
•pituitary gland problem
•previous heart attack
•an unusual or allergic reaction to levothyroxine, thyroid hormones, other medicines, foods, dyes, or preservatives
•pregnant or trying to get pregnant
•breast-feeding

How should I use this medicine?

Take this medicine by mouth with plenty of water. It is best to take on an empty stomach, at least 30 minutes before or 2 hours after food. Follow the directions on the prescription label. Take at the same time each day. Do not take your medicine more often than directed.

Contact your pediatrician regarding the use of this medicine in children. While this drug may be prescribed for children and infants as young as a few days of age for selected conditions, precautions do apply. For infants, you may crush the tablet and place in a small amount of (5-10 ml or 1 to 2 teaspoonfuls) of water, breast milk, or non-soy based infant formula. Do not mix with soy-based infant formula. Give as directed.

Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.
NOTE: This medicine is only for you. Do not share this medicine with others.

What if I miss a dose?

This does not apply.

What may interact with this medicine?

•amiodarone
•antacids
•anti-thyroid medicines
•calcium supplements
•carbamazepine
•cholestyramine
•colestipol
•digoxin
•female hormones, including contraceptive or birth control pills
•iron supplements
•ketamine
•liquid nutrition products like Ensure
•medicines for colds and breathing difficulties
•medicines for diabetes
•medicines for mental depression
•medicines or herbals used to decrease weight or appetite
•phenobarbital or other barbiturate medications
•phenytoin
•prednisone or other corticosteroids
•rifabutin
•rifampin
•soy isoflavones
•sucralfate
•theophylline
•warfarin

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

What should I watch for while using this medicine?

Be sure to take this medicine with plenty of fluids. Some tablets may cause choking, gagging, or difficulty swallowing from the tablet getting stuck in your throat. Most of these problems disappear if the medicine is taken with the right amount of water or other fluids.

Do not switch brands of this medicine unless your health care professional agrees with the change. Ask questions if you are uncertain.

You will need regular exams and occasional blood tests to check the response to treatment. If you are receiving this medicine for an underactive thyroid, it may be several weeks before you notice an improvement. Check with your doctor or health care professional if your symptoms do not improve.

It may be necessary for you to take this medicine for the rest of your life. Do not stop using this medicine unless your doctor or health care professional advises you to.

This medicine can affect blood sugar levels. If you have diabetes, check your blood sugar as directed.

You may lose some of your hair when you first start treatment. With time, this usually corrects itself.

If you are going to have surgery, tell your doctor or health care professional that you are taking this medicine.

What side effects may I notice from receiving this medicine?

Side effects that you should report to your doctor or health care professional as soon as possible:
•allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue
•chest pain
•excessive sweating or intolerance to heat
•fast or irregular heartbeat
•nervousness
•skin rash or hives
•swelling of ankles, feet, or legs
•tremors
 
Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):
•changes in appetite
•changes in menstrual periods
•diarrhea
•hair loss
•headache
•trouble sleeping
•weight loss
 
This list may not describe all possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Where should I keep my medicine?

Keep out of the reach of children.

Store at room temperature between 15 and 30 degrees C (59 and 86 degrees F). Protect from light and moisture. Keep container tightly closed. Throw away any unused medicine after the expiration date.

Last updated: 3/20/2006 11:23:00 AM

Important Disclaimer: The drug information provided here is for educational purposes only. It is intended to supplement, not substitute for, the diagnosis, treatment and advice of a medical professional. This drug information does not cover all possible uses, precautions, side effects and interactions. It should not be construed to indicate that this or any drug is safe for you. Consult your medical professional for guidance before using any prescription or over the counter drugs.

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Saunders Veterinary Dictionary:

levothyroxine

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Home > Library > Animal Life > Veterinary Dictionary

The pharmaceutical name for the thyroid hormone thyroxine (T4); used for replacement therapy in hypothyroidism.

Mosby's Dental Dictionary:

levothyroxine sodium

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Home > Library > Health > Dental Dictionary

n

trade names: Levo-T, Synthroid; drug class: thyroid hormone; action: increases metabolic rate, with increase in cardiac output, O2 consumption, body temperature, blood volume, growth/development at cellular level; uses: hypothroidism, myxedema coma, thyroid hormone replacement, cretinism.

Wikipedia on Answers.com:

Levothyroxine

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Home > Library > Miscellaneous > Wikipedia
Levothyroxine
Systematic (IUPAC) name
3,5,3',5'-Tetraiodo-L-thyronine
Clinical data
Trade names Euthyrox among others, Synthroid, Thyrax
AHFS/Drugs.com monograph
MedlinePlus a682461
Pregnancy cat. A(US)
Legal status ℞ Prescription only
Routes Oral, Intravenous
Pharmacokinetic data
Bioavailability ~100%
Metabolism Mainly in liver, kidneys, brain and muscles
Half-life ca. 7 days (in hyperthyroidism 3-4 days, in hypothyroidism 9-10 days)
Excretion Through feces and urine
Identifiers
CAS number 51-48-9 YesY
ATC code H03AA01
PubChem CID 5819
DrugBank APRD00235
ChemSpider 5614 YesY
UNII Q51BO43MG4 YesY
ChEBI CHEBI:18332 YesY
ChEMBL CHEMBL1624 YesY
Synonyms O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-L-tyrosine
Chemical data
Formula C15H11I4NO4 
Mol. mass 776.87
SMILES eMolecules & PubChem
 N(what is this?)  (verify)

Levothyroxine, also L-thyroxine, synthetic T4, or 3,5,3',5'-tetraiodo-L-thyronine, is a synthetic form of thyroxine (thyroid hormone), used as a hormone replacement for patients with thyroid problems. The natural hormone is chemically in the chiral L-form, as is the pharmaceutical agent. Dextrothyroxine (D-thyroxine) briefly saw research as an anticholesterol agent but was pulled due to cardiac side-effects.

Contents

Medical uses

Levothyroxine is typically used to treat hypothyroidism.[1] It may also be used to treat goiter via its ability to lower thyroid-stimulating hormone (TSH), a hormone that is considered goiter-inducing.[2][3]

Adverse effects

Dosing must be carefully controlled to achieve TSH levels within the normal reference range. Long-term suppression of TSH values below normal values will frequently cause cardiac side-effects and contribute to decreases in bone mineral density (high TSH levels are also well known to contribute to osteoporosis).[4]

Patients prescribed too high a dose of levothyroxine may experience effects that mimic hyperthyroidism.[5] Overdose can result in heart palpitations, abdominal pain, nausea, anxiousness, confusion, agitation, insomnia, weight loss, and increased appetite.[6] Allergic reactions to the drug are characterized by symptoms such as difficulty breathing, shortness of breath, or swelling of the face and tongue. Acute overdose may cause fever, hypoglycemia, heart failure, coma and unrecognized adrenal insufficiency.

Acute massive overdose may be life-threatening; treatment should be symptomatic and supportive. Massive overdose may require beta-blockers for increased parasympathetic activity.[5]

The effects of overdosing appear 6 hours to 11 days after ingestion.[6]

Interactions

There are also foods and other substances that can interfere with absorption of thyroxine replacement. People ought to avoid taking calcium and iron supplements within 4 hours,[7] as well as soy products within 3 hours of the medication, as these can reduce absorption of the drug. Grapefruit juice may delay the absorption of levothyroxine, but it is not believed to have a significant effect on bioavailability.[8] Other substances that reduce absorption are aluminium and magnesium containing antacids, simethicone or sucralfate, cholestyramine, colestipol, Kayexalate. A study of eight women suggested that coffee may interfere with the intestinal absorption of levothyroxine, though at a level less than eating bran.[9] Different substances cause other adverse effects that may be severe. Ketamine may cause hypertension and tachycardia and tricyclic and tetracyclic antidepressants increase its toxicity. On the other hand lithium can cause hyperthyroidism (but most often hypothyroidism) by affecting iodine metabolism of the thyroid itself and thus inhibits synthetic levothyroxine as well.

Dosage

Generic Levothyroxine, 25 MCG Oral Tablet

Dosages vary according to the age groups and the individual condition of the patient, body weight and compliance to the medication and diet. Monitoring of the patient's condition and adjustment of the dosage is periodical and necessary. Levothyroxine is taken on an empty stomach approximately half an hour to an hour before meals.[5]

Brand names

Common brand names include Thyrax, Euthyrox, Levaxin, L-thyroxine, Eltroxin and Thyrax Duotab in Europe; Thyrox in South Asia; Eutirox, Tirosint, Levoxyl and Synthroid in North America. There are also numerous generic versions.

References

  1. ^ Vaidya B, Pearce SH (2008). "Management of hypothyroidism in adults". BMJ (Clinical research ed.) 337: a801. doi:10.1136/bmj.a801. PMID 18662921. http://bmj.com/cgi/pmidlookup?view=long&pmid=18662921. 
  2. ^ Svensson J, Ericsson UB, Nilsson P, et al. (May 2006). "Levothyroxine treatment reduces thyroid size in children and adolescents with chronic autoimmune thyroiditis". The Journal of clinical endocrinology and metabolism 91 (5): 1729–34. doi:10.1210/jc.2005-2400. PMID 16507633. http://jcem.endojournals.org/cgi/pmidlookup?view=long&pmid=16507633. 
  3. ^ Dietlein, M; Wegscheider, K; Vaupel, R; Schmidt, M; Schicha, H (2007). "Management of multinodular goiter in Germany (Papillon 2005): do the approaches of thyroid specialists and primary care practitioners differ?". Nuklearmedizin. Nuclear medicine 46 (3): 65–75. PMID 17549317.  edit
  4. ^ Frilling, A; Liu, C; Weber, F (2004). "Benign multinodular goiter". Scandinavian journal of surgery : SJS : official organ for the Finnish Surgical Society and the Scandinavian Surgical Society 93 (4): 278–81. PMID 15658668.  edit
  5. ^ a b c "Synthroid (Levothyroxine Sodium) Drug Information: Uses, Side Effects, Drug Interactions and Warnings". RxList. http://www.rxlist.com/synthroid-drug.htm. Retrieved 2010-07-18. 
  6. ^ a b Irizarry, Lisandro (2010-04-23). "Toxicity, Thyroid Hormone". WebMd. http://www.emedicine.com/emerg/TOPIC800.HTM. Retrieved 2010-10-31. 
  7. ^ Ruth H. Michel, Patricia J. Neafsey, Laura Cox Dzurec: Self Medication Practices among Patients taking Levothyroxine. The Internet Journal of Advanced Nursing Practice. 2004. Volume 6 Number 2
  8. ^ Lilja JJ, Laitinen K, Neuvonen PJ (September 2005). "Effects of grapefruit juice on the absorption of levothyroxine". Br J Clin Pharmacol 60 (3): 337–41. doi:10.1111/j.1365-2125.2005.02433.x. PMC 1884777. PMID 16120075. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1884777. 
  9. ^ Benvenga, Salvatore; Bartolone, L.; Pappalardo, M.A.; Russo, A.; Lapa, D.; Giorgianni, G.; Saraceno, G.; Trimarchi, F. (March 2008). "Altered Intestinal Absorption of L-Thyroxine Caused by Coffee". Thyroid (New York: Mary Ann Liebert, Inc.) 18 (3): 293–301. doi:10.1089/thy.2007.0222. PMID 18341376. http://www.ncbi.nlm.nih.gov/pubmed/18341376?dopt=Citation. Retrieved 2009-05-16. 

External links

Thyroid therapy (H03)
Thyroid hormones
Levothyroxine# • Liothyronine • Tiratricol • Thyroid gland preparations
Antithyroid preparations
Block conversion of
T4 to T3
Other

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

 
 

 

Copyrights:

Drug Info. Gold Standard. Copyright © 2008 by Gold Standard. All rights reserved.  Read more
Saunders Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Mosby's Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
Wikipedia on Answers.com. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Levothyroxine.  Read more