- Hyperthyroidism Slideshow Pictures
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- Thyroid Symptoms and Solutions Slideshow Pictures
- What is levothyroxine sodium, and how does it work (mechanism of action)?
- What brand names are available for levothyroxine sodium?
- Is levothyroxine sodium available as a generic drug?
- Do I need a prescription for levothyroxine sodium?
- What are the side effects of levothyroxine sodium?
- What is the dosage for levothyroxine sodium?
- Which drugs or supplements interact with levothyroxine sodium?
- Is levothyroxine sodium safe to take if I'm pregnant or breastfeeding?
- What else should I know about levothyroxine sodium?
What is the dosage for levothyroxine sodium?
For adult hypothyroidism, levothyroxine is started at 12.5-125 mcg/day administered orally. Starting doses and dose changes may differ with individual patients based upon age, the presence of cardiovascular disease, the development of tolerance (reduced effectiveness with continued use), side effects to the medication, and blood levels of thyroid hormone. It may take one to three weeks after initiating therapy with levothyroxine or changing the dose before effects are seen. The goal of replacement therapy is to maintain a normal blood thyroxine level.
Which drugs or supplements interact with levothyroxine sodium?
Initiation or discontinuation of therapy with levothyroxine in diabetic patients may create a need for an increase or decrease in the required dose of insulin and/or antidiabetic drug, (for example, glyburide [Micronase]).
Intravenous administration of epinephrine to patients with coronary artery disease may lead to complications ranging from difficulty in breathing to a heart attack. These complications may occur more frequently among patients also taking levothyroxine. Therefore, careful observation is needed when intravenous epinephrine is given to patients receiving levothyroxine who also have coronary artery disease.
Converting a state of hypothyroidism (under activity) to a normal state (euthyroid state) with levothyroxine may decrease the actions of certain beta-blocking drugs, (for example, metoprolol [Lopressor] or propranolol [Inderal]). It may be necessary, therefore, to change the dose of beta-blocker. For the same reason, the dose of digoxin (Lanoxin), a drug used to manage heart failure or an irregular heart rhythm (for example, atrial fibrillation), also may need to be changed.
Taking levothyroxine at the same time as calcium carbonate, ferrous sulphate, cholestyramine (Questran) or colestipol (Colestid) may decrease the effect of levothyroxine and lead to hypothyroidism. This occurs because the levothyroxine binds to these drugs and is not absorbed. Taking the levothyroxine one hour before or four hours after these drugs is necessary to prevent binding.
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